I have been brainstorming ideas for where to build a high security shelter. I live in a suburban house, built in the mid-1960s.
We could allocate a room in our basement for this, but my wife will probably object to the loss of living space. The next possibility might be to dig out an area beneath our garage, which is attached to the house. Does anyone here have experience with the "garage retrofit" approach?
Pro:
+ No impact on existing living space
+ Easier to hide the secure area from searchers (If the shelter were built in our basement, its presensence would be obvious to visitors.)
Con:
- Obvious "major" construction project would attract attention of neighbors and building inspectors.
- May affect the house foundation.
- Heavy equipment on the brick driveway leading to the garage may damage the bricks.
- Would have to cut an entrance in the current foundation wall from basement through to new shelter.
Please share your suggestions and opinions.
I know someone who has done it, although I think they did not excavate under the entire garage. They only did a portion of it. I have not seen the shelter but the person who told me they did it said they dug it out a little at a time and dumped buckets of dirt into the neighboring field. They did not use heavy equip. for obvious reasons. This person also recommended that instead of doing that, it would be better to create a patio or something under a deck. I presume the reason they said this was either they thought the "under the garage" approach was too hard or there were some other design or engineering aspects/costs that could be avioded by making a patio on one part of your house.
I started an E-mail thread a long time ago about creating this patio thing, but have not yet figured out how to do it. A respondee to my original message (read about it in this same section of Joel's forums) talked about how hard it is to cut into an existing foundation. We should talk on the phone about this as I have a lot of other details/ideas that are too extensive to put in an E-mail thread. Respond to me if you are interested in talking and include your phone number.
I thought of putting in the shelter, then pouring a slab around it and erecting one of those pre-fab gazebos you can order at Home Depot or Lowe's with a big umbrella awning that can be used to hide some vents or antennas. All you would need to do is make a floor in the gazebo. You could use the space between the shelter lid and the gazebo floor for re-inforced (ballistically) viewing ports.
digging into an existing foundation brings the risk of cracking the existing work and besides, its probably already well settled already. It just never looks right, or at least it takes a long time to make it look like it matches.
OK... perhaps digging under/through an existing concrete slab in my garage is too much work and risks damaging existing structure.
Plan B is to dig out the crawl space... bucket by bucket. I don't relish the effort ahead of me, but I suppose I'll be toughened by it. It'll take me months, but the work will be discrete.
Does anyone have any concerns about digging down into the crawl space of a house? I don't think dampness will be a big issue, since my crawl space is bone dry.
Plumbing outflow is a concern. If the floor of my shelter is lower than my house basement floor, I may have to raise the toilet and sink well above the shelter's floor to ensure proper drainage.
Suggestions?
To comment on some of your concerns:
Plumbing: Ejector pumps are common when sewer/septic lines are above desired toilet/sink.They drain into a closed sump container buried at a lower level which contains a macerator to grind waste and an ejector pump to pump waste up or horizontally. power is required for motors. If distance is not great, a hand pump marine or RV version might work. Crawl space or garage digout: foundations are not deep enough and if your dig near them without support you will cause the structure above to collapse! Probable most strict building code in country requires footing(base for foundation wall) at a depth of four feet. Garages are not heavy and in your area may require only two foot deep foundation! You can dig holes (one at a time - do not start #2 until #1 is completed and cured) at an angle next to foundation to insert a steel column, set on a proper concrete base, and then stood upright under existing foundation to support it. This procedure is called "underpinning" and should be designed by a structural engineer - likewise, digging a smaller space within the boundries of shallow foundations can lead to collapse of both digout area and structure above due to lateral forces.Not inexpensive or discrete solutions. But, good news is that you can safely "punch" a doorway through your existing basement wall because you already have foundation base below it to support lintel which supports structure above. Any competent local builder can do/advise. Outside of this "exit" I would have steps/ramp down to desired level(floor of new "root cellar"), through short(4-8ft)section of concrete sewer pipe"hallway" to security entrance door to new shelter. In addition to Joel's books, see finalphase.com for shelter solutions.
Thank you for your practical advice, Rokonmi. You may have saved me a very expensive mistake... undermining my own foundations! This makes me reconsider sacrificing a room in my basement.
You could add the patio outside with a shelter under it, and then conceal a tunnel from the basement to the shelter using corrugated culvert. The culvert wouldnt need to be extremely deep, just maybe 3 or 4 feet down perhaps, but lay a bunch of scrap chain link fence, old wire, some ready-mix to stiffen the whole mess up, whatever that would make it a real tough job for anyone with handtools (cause thats all thats gonna be left later on)to dig it up.
I dont know a slick way to quietly excavate and then put a shelter in the open, unless you do it fast, which costs $$$. There are prefab fiberglass shelters that are claimed to be installable in 1 day if the excavation is pre-prepared. I have seen the fiberglass shelters on www.gasmasks.com
If you dont have enough land or seclusion to prevent nosy neighbors, maybe you would need to do it one bucket at a time like you say. Its tough work, but its worthwhile. Beats breaking your keester for a faceless corporation, doesnt it?
I know these are "old" postings, but I was wondering how TrueNorth's home shelter is going? I've been reading everything I can get my hands on about shelters. One thing that's come up frequently is NOT to build a shelter in your basement (in case house catches on fire) or too close to buildings because smoke, if they should catch fire, would be toxic. I'm new to all of this; by no means an expert on the subject. What does anyone else think?
Status Update: I have started building a concrete water cistern next to my house foundation. It will hold about 1000 gallons. I have almost completed digging the hole (by hand, as I live in a suburban environment and do not have space for a back-hoe).
The cistern excavation will give me an opportunity to examine the type of foundation my house has. A friend (local foundation repair specialist) says that a lot of homes in my area are built on case-ons (sp?), which are like concrete piles. This design counteracts the foundation disturbances caused by soil expansion (high bentonite content). Anyway, I've got a few more feet of cistern digging before I can determine whether my house has a standard footing or these "case-ons". If the latter, my friend says that my house foundation probably WON'T be compromized/disturbed by excavating the crawl space, since the foundation rests on the case-on itself, not the footer sill. If that's the case, I'll dig, dig, dig to excavate my crawl space for the high security shelter. The excavating will take me until after August 2002. Then I'll begin work on the frame.
In the mean time, I will purchase strategic supplies. I already have a set of Honeywell CPZ and HEPA filters. I also got a pair of calibrated quality radiation meters for about $20 each on eBay (before Sept 11).
Soon I will get a set of deep cycle batteries, a trickle charger, and perhaps a solar panel. I am considering gettng a ham radio license.
The shelter door is another area ready for investigation. Vault doors are now very expensive. I'm considering a steel utility door filled with gravel as Joel suggests.
All this is keeping me busy... with my other responsibilities (bed time stories for the kids, etc.)
Happy to hear of your progress and potential use of your crawl space idea. I once lived on a man-made island which was constructed by driving seawall - 4" thick hemlock boards driven into lake bed, secured on the inside, pumped-out free of water,and filled in with dirt. Foundations were built by driving 6" dia pipes, welding on additional sections, until they hit bedrock 40, 50, 60ft. Pipes were driven at 8' intervals to outline foundation of house and "bridging steel" welded to top of ground level pipes became base for building. At this point, basements were dug within the secure foundation structure and concrete poured. After 35+ years, mild earthquakes, freeze-thaw cycles, and 80+ buildings, there has not been even minor failure! The pipe/pile/pole/caison you describe is a well documented winner! Keep in mind though: 1. pole/caison must be "securely grounded" (resting on bedrock or virgin soil below your frost depth, and 2.You cannot dig below the level(depth) of your current caisons at any area too close to them
One concern I have of homes built before 1980 is the asbestos commonly used in the popcorn ceilings and in the flooring (vinyl and adhesives). (The firefighters, police, and rescue workers at the WTC were victims of this). Seems better to either have your house tested for this before considering a basement shelter or opt for the garage.
Status Update: I have been excavating the crawl space for five weekends now. Two of my friends are helping me. We fill 5 gallon buckets, pass them out the crawlspace and haul them out of the house.
We work four hour shifts. That's long enough for a desk-jockey like me. We track our progress (count the number of wheelbarrow loads, with 5 buckets of dirt per wheelbarrow.)
Soon we'll cut the 9" thick basement wall to enlarge the crawlspace opening to be door-sized. The very heavy 3'x4'x9" slab will fall inward into the crawl space into a "grave" that we've dug. I will lay ropes in the grave to assist us with manouvering the slab in case it doesn't fall the way I'd like. Once it's flat, the concrete floor will be poured over it.
Excavating with buckets is made more efficient if you find ways to minimize the amount of shoveling. We do this by digging a deep trench and then enlarging it. As we widen the trench, we work from top downward. The dirt near the top of the trench is dislodged (with pick or electric jack hammer) and is caught by the buckets. When the bottom row of buckets are nearly full, a second row of empty buckets is placed on top of the full ones. They too are filled with cascading dirt. Gravity does our work and this technique minimizes the amount of dirt that's lifted with a shovel.
When we're moving a low pile of soft dirt (or gravel) we grab a bucket with both hands and ram it into the pile to scoop as much as we can. Leaving the bucket tipped over on its side, we straddle it and use a small shovel to pull dirt into the bucket. It's quicker to move the loose dirt horizontally into the bucket than filling it the "regular" way.
The dirt in my crawlspace is hard packed, except for the top 12" which is powder dry. The deeper we dig the wetter it gets. We'll be digging to within 18" of the footer. (We're digging 6 feet lower than the footer.) The soil under the footer is very stable. To ensure that we don't undermine it (causing the load bearing wall to collapse), I'll be building two support posts 10' in from each end of the 26' long footer. These posts will rest on 2'x2' concrete pads. The posts will be made from cinder block reinforced with rebar and mortar.
I have excavated a hole under the footer. It will serve as an alternate exit. It's also where the concrete pumper truck will snake its hose in order to pour the floor.
I will pour a concrete cistern at the same time as the floor is poured.
>I have excavated a hole under the footer< You are "underpinning" your foundation (which is not now on posts/pilings/casions)? I would span the posts with steel I-beam as wide as foundation (beam immediately under foundation and on top of posts). Sounds like you have developed the physical and mental stamina for survival! Will your new shelter be large enough & available to your helpers? What do your inevitably curious neighbors think is going on? I am happy to hear of your progress and innovative solutions to the hard work at hand! Keep us posted!
several more comments: pads for your new posts should be sized as if they are "footers for your foundation wall" - in other words 1.5 to 2 x wider than width of wall they are supporting - consult a book re "footers". Also in cutting crawl space wall, are you using gas powered concrete saw?? Remenber that CO-2 falls to lowest point - heavier than oxygen AND IS ODORLESS AND CAN KILL YOU! Make 3-sided plywood box to support a good exhaust fan and connect to exit of fan flexible duct(home depot, heating & cooling shop) & put exit hose outside so CO-2 cannot fall back into your work space!!!
Thanks for your interests and comments, Rokonmi. My shelter will be 25'x7'x7' (internal dimensions). This will be sufficient for my family, but does not leave much room for others on a long term basis. We may be able to accommodate one or two "guests". My helpers are being paid for the work they do for me. I would like to build something big enough to support everyone I care about, but I cannot. Hard decisions.
My helpers understand this project as a "secure, fire-proof storage area". (Which it will be.) When we travel for extended periods, we will move some of our valuables into the fireproof storage area. Our curious friends and neighbors know that we are building a storage area in the crawlspace. That satisfies their curiosity without requiring me to be deceptive.
Thanks for your concerns about carbon monoxide (CO) poisoning. I'll have a contractor cut the wall. I beleive he'll use a hydraulic saw, so that eliminates the fumigation problem. A compressor at his truck pumps hydraulic fluid down some lines to the saw. The moving fluid spins the blade.
The foundation footer "underpinning" is being done as a precaution in case of earthquake. I believe the soil in place under the short foundation wall will be strong enough to support its load under normal circumstances.
Perhaps the cryptic diagram below will give you a better idea of what I'm doing. Note: This diagram will look goofy unless you view it in a non-proportional font like Courier. Copy and paste it into Notepad or MS Word and change the font to Courier.
w = concrete wall
f = concrete footer
h = hole I'm digging
s = compact soil (like clay)
j = wooden floor/ceiling joists
www.............................www
wwwjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj
www.............................www
www.............................www
ssswww.............................www
ssfffff............................www
ssfffff............................www
ssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhwww
ssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhwww finished
ssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhwww basement
ssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhwww
ssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhwww
ssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhwww
ssssssssshhhhhhhhhhhhhhhhhhhhhhhhhfffffffffffffff
ssssssssshhhhhhhhhhhhhhhhhhhhhhhhhfffffffffffffff
ssssssssshhhhhhhhhhhhhhhhhhhhhhhhhsssssssssssssss
ssssssssshhhhhhhhhhhhhhhhhhhhhhhhhsssssssssssssss
ssssssssshhhhhhhhhhhhhhhhhhhhhhhhhsssssssssssssss
sssssssssssssssssssssssssssssssssssssssssssssssss
Once the hole (h) has been dug, I'll support the short left hand wall with two piers (P) made from cinder block build on poured footers. Then I'll pour a concrete floor (F), then build cinder block walls (W) and a cinder block roof (R).
wwwjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj
www.............................www
www...RRRRRRRRRRRRRRRRRRRRRRRRR.www
ssswww...WW.....................WW.www
ssfffff..WW.....................WW.www
ssfffff..WW.....................WW.www Entrance
sssPPPsssWW.....................WW.www <====
sssPPPsssWW.....................WW.www finished
sssPPPsssWW.....................WW.www basement
sssPPPsssWW......Shelter........WW.www
sssPPPsssWW.....................WW.www
sssPPPsssWW.....................WW.www
sssPPPsssWW.....................WWfffffffffffffff
sssPPPsssWW.....................WWfffffffffffffff
sssPPPsssWW.....................WWsssssssssssssss
sssPPPsssWW.....................WWsssssssssssssss
sssPPPsssFFFFFFFFFFFXXXXFFFFFFFFFFsssssssssssssss
ssPPPPPsssssssssssssXXXXsssssssssssssssssssssssss
ssssssssssssssssssssXXXXsssssssssssssssssssssssss
Lastly, I'll build an alternative exit (X) that travels under a foundation wall, under the concrete water cistern, and up, on the other side of the cistern.
Sounds like you have handled the worker and curious others well! Your plan seems well thought out and executed and should be an inspiration for others, even of limited resources and circumstances, to use their heads and backs and do what is necessary! Keep us posted as to progress and other info which would be helpful to others - thanks!
Status Update: For $250 I hired a local concrete cutter to enlarge the opening to my crawl space. He cut through my 9" concrete wall with a hydraulic saw from the inside of the crawl space. (I'd dug a deep hole into which the 3'x4' slab would fall and be buried.) I masked off the furnace room with plastic sheeting, because his saw uses water to control the dust. (Instead of dust you get grey sludge flung everywhere!) His cuts were 8" deep (so not to spray the furnace room excessively). He then used a sledge hammer to dislodge the slab.
Because concrete weighs about 150lbs per cubic foot, I had him cut the slab into two pieces. (2" x 3" each). This made it easier for me to manouver them into position at the bottom of the hole.
We started by toppling only one into the hole. (Two blocks would interfere with each other and make our time in the hole more dangerous. (no crushed toes, thank you)) To manouver the block, a friend and I "walked" it into position, then fine-tuned its position by drilling an anchor hole in the center of the slab, pounding in an anchor, placing another anchor in the foundation wall high above, then using a truck tie down strap and its ratchet to lift the block enough to move it into its final resting spot.
Once the first block was positioned, we pushed the second slab into the hole and repeated the steps with the second block. The two blocks now lie side by side.
Now that the crawl space is easy to get into and out of, this weekend a bunch of friends will work our hard to excavate about 12 yards of the remaining dirt from the crawl space -- bucket by bucket.
Good report. I like your creativity to move the slabs. Keep your inspirational reports comig!
Status Update: Over 2/3 of the soil in my crawlspace is now gone! I have one pillar built and another one goes up this week. These pillars support the footer of the short foundation wall (26' long) that I've excavated beside.
First, I dug down to undisturbed soil (hard packed rock-like dry clay about 8 feet below the footer. Then I poured a 24"x30"x10" 5000 psi concrete footer reinforced with #5 rebar. After that, I built a column of cinder blocks, filled with mortar and rebar. Hand-packed concrete fills the 5" gap between the top of the 18"x18"x7' column and the original foundation footer.
I expect (hope!) that these two piers/columns will be sufficient support for the load bearing foundation wall.
The soil that remains under the original footer is densely packed and seems stable. I've needed a pick or jackhammer w/ clay spade to loosen it before it could be shovelled into buckets. I'm hoping this soil will bear the weight of the load bearing wall and that the columns I've built will only be required if the earth shifts (earth tremor/quake).
Except for the two 8' vertical holes that have been dug directly under the foundation wall, the remaining segment of the foundation wall has soil that comes up to within one foot of the footer. This remaing 1' will be removed about a month and a half after the second concrete column has been built.
I'm tired of digging and will be taking a break for a while. I've lost 10 pounds off a body that didn't have much weight to lose in the first place. Each week for the past six weeks I've spent about 8 hours digging or hauling sacks of concrete. My wife wishes she could lose weight as easily.
I've been tracking my efficiency. My friends and I excavate between 4 and 5 wheelbarrow loads per person per hour. That involves loosening soil with a pick or jack hammer, scooping it into buckets, carrying the buckets up stairs to ground level, dumping them into a wheelbarrow (5 buckets per load), wheeling the wheelbarrow to a dumpster, then returning the empty buckets to the hole. Last Saturday, in a burst of energy, a friend and I moved 14 wheelbarrow loads in a single hour. That's the record so far, but not sustainable.
I learned that a "20-yard" dumpster does not actually contain 20 cubic yards. This meant that I had to have the dumpster emptied and replaced more often than I expected. At $275 per load it can add up, so I called the disposal company and explained that my dumpsters were far overweight. (They told me their limit was 10 tons, and I had about 37,000 pounds of dirt already piled into it.) They offered to pick up the dumpster in the evenings when the dump's scales were closed. (They get a $2000 fine if their trucks are caught overweight.)
Surprisingly, my friends that have desk jobs are the most willing to help with the excavation work. They like the idea of doing physical work for a change. Some of my "blue collar" friends worked very hard too, but my weekend work was too similar to their real work for them to get excited about it.
This concrete pillar work is the first structural project I've done. I learned that the concrete must not dry too fast... otherwise it'll not reach its full strength. For a week or so I pour water on the cinder blocks each day. I'm amazed that they act like a sponge and absorb a lot of water.
This leads me to wonder whether I should put a layer of plastic between the vertical wall of soil and the cinder block shelter walls when I begin building them. If I don't find some way to seal the cinder block, I expect my shelter will be damp as the cinder block seems to absorb water. This may cause the interior paint to peel. (Using 6" blocks for the walls, my shelter will have an internal width of only 7' so I don't think I can afford to give up interior space to drywall and studs.) Does anyone have experience with cinder blocks contacting damp soil?
I've been building in North and South Carolina for the past two years--using exclusively cinder blocks for foundation material.
You're right about the sponge-like attributes of these (as with all masonry material) blocks. Unless you want a permanently damp interior, your best bet would be to seal the outside of the cinderblock wall.
There are many different types of products that can accomplish this--from rubber-based, to asphalt emulsion. The best idea for your situation would probably be a mortar-based product such as Thuro-seal (I think that's the spelling). You mix it like a very thin mortar, and then brush or roll it on. It's not cheap, but usually cheaper than rubber-based, and easier on the fumes. Anyway, for every course of block you lay, come back through and seal the outside as you go. Make sure you overlap the mortar joints as you go up. Once you are done, a roll of plastic over the top of the Thuro-seal would be a good idea for extra protection.
No matter how good you seal your shelter, it will still be humid. Water has a way of getting into the air--especially in places like under your home. Future de-humidifying plans should also be in the works.
By the way, any groundwater issues where you are digging?
One more thing about dirt removal.
There are often local builders looking for "clean fill" meaning only dirt and masonry material--like broken concrete, rocks, and cinder blocks. I had my dumpster company actually dump two full 30 yd dumpsters for free because they found someone who would take the dirt a few miles away. Otherwise, they were going to charge me a reduced fee (about 33% of the normal charge) for dumping the dirt because it was "clean fill". Maybe you could get them to reduce the price a bit because the contents aren't typical construction debris.
Regarding groundwater: I've got a french drain running under my house foundation, just below the level of the shelter floor. I plan to run a few "mini drains" under my shelter floor to connect to the existing french drain. These new drains should funnel any water away from the base of the shelter wall that faces the damp dirt (garden-side).
The dirt in my crawl space is dry on the surface and grows damp (but not wet) as I go deeper. No mud. No water has formed in the holes I've dug so far.
AB, thanks for the tips regarding soil removal and sealing cinder block. I may have a hard time sealing the cinder block on the side that needs sealing the most, since I'll be building the wall right against a wall of dirt that reaches vertically to the inside edge of the original footer 7 feet above. I would have to undermine the footer a bit to give me space to apply the sealer, but for stability reasons, I don't want to undermine the footer at all (except where the two supporting piers/columns are built). This will require a creative solution. Ideas?
The best solution I can think of would be to place a continuous piece of heavy-duty plastic up against the dirt before laying the block. The thinner plastics aren't a complete water-proofing vapor barrier. Don't quote me on this one, but I believe 6 mil. would be sufficient, and strong enough against tears.
One additional idea, would be to seal the face of each block before placing it. Make sure you don't seal the top and bottom as a porous surface will be necessary to "absorb" and get a good grip on the mortar in between.
Will these block walls have to carry the weight of any dirt behind them--think worst-case scenario. If so, have you compensated for the lateral pressure you expect to have?
AB in SC brings up a point that i mentioned before - lateral forces. Consider adding a grid,both vertical & horizontal of 5/8 rebar in the cavities of block as you built - refer to Joel's book for starting point of how to do this.Also, as AB says, "water ALWAYS wins" - you should try to be as waterproof as possible but will potentially still be damp. Don't forget the floor also! If you have room, it might be nice to totally enclose space within which you will built with a rubber membrane and even solid board insulation. If you only seal outside of blocks as you built, it still leaves mortar joints exposed to suck in moisture
Thanks for the suggestions, fellows.
Regarding solid board insulation: In the book "No Such Thing as Doomsday" the author discusses the necessity of a heat sink in case the shelter is occupied for a long period. Do you think that solid board insulation between the dirt and the cinder blocks would eliminate the benefit of a heat sink? It seems to me that body heat in a confined space could keep the shelter warm enough. (I will lay a thin wood subfloor and then carpet it, so my tootsies are sure to stay warm.) At some point the body heat may become too much... and that's when I'd need the earth to act as a heat sink. Thoughts?
I see your point; maybe insulate only under floor.
If you leave either the blocks or the floor uninsulated, you will still have a heat sink. If you fill the cells solid, heat will be transferred more through the walls, but if you leave them hollow, then the floor will be the greatest heat sink as solid masonry/concrete transfers more energy than hollow.
Even if you insulate the ouside of the blocks, the heat will still be transferred from the blocks down to the floor and footings of your wall. That may be a good idea as most block waterproofing I've seen has been combined with a solid foam board (extruded, not expanded polystryrene) on the outside.
Insulating the outside of your block will aid in the waterproofing because as you generate moisture by living inside the shelter, the water vapor will transfer through the walls until it gets close enough to the cooler temperatures on the outer edge of the block where it will condense, and basically saturate your blocks. By insulating the outside of the wall, the vapor is less likely to condensate as it approaches the outer edge of your block. You will still need to remove the moisture from your shelter--probably through a de-humidifier or air filtration/air exchange, but at least it won't be condensing in your walls where mold and mildew can then become a problem.
Status Update: There is water in the crawlspace hole I've been excavating by hand. I have returned to my "digging project" after 2 1/2 months off. When I stopped in early April I had two pillars built (about 7' tall) to support the foundation wall I was excavating beside. In the months since then, an irrigation ditch started flowing behind my house (about 50' away from my foundation wall, slightly uphill). Water is seeping in around the pillars I built. When I investigated recently, it had pooled, but seeped into a french drain that runs along the edge of my interior basement wall. Fortunately it didn't flood into my basement. We're having an unusually dry season, so I'm a bit nervous about what might happen if the flow rate increases.
At this point I'm considering installing a sump pump as a backup in case the french drain gets overwhelmed. I can pump the water into another french drain that I built two years ago. It is made from 3" pipe and runs out to the street.
I reckon I've got another full dumpster load of dirt (now turned to mud) to move before I can work on the sump pump and other under-floor drains that will lead to it. At that point I'll be able to pour a concrete floor. I want to make sure I've got the drainage situation handled before I pour the concrete. It'll be hard to fix after that's done.
I spent a dirty morning scooping mud away from the base of the 2'x3' concrete pad that one of my cinder-block pillars rests on. I noticed a disturbance (water movement) that seemed to indicate water flowing UNDER the concrete pad. It was a small amount, but enough to make a little upwelling that swirled grains of sand (but didn't "spit them out" into a pile).
Any thoughts and suggestions are welcome.
If you are going to use a sump pump, it would be better, though more expensive, if you caught the water before it entered withing the footprint of your foundation. I would trench around outside the house and then try to drain the water down-hill (topography-permitting) to drain out without any requred electrical pumping. Nothing worse than a faied sump pump, or extended power outage to ruin plans of a "dry" shelter.
Sounds like the water might be undermining the structural integrity of your pillars, so you probably don't want to wait too long to resolve this issue. Plus, excessive humidity in a crawl space has been known to rot the exposed lumber in just a few short years.
Look into renting a small backhoe for a day or two. They will deliver it, and for just a few hundred dollars, you will be able to dig your own trench to divert the water before it gets to the house. Dig it as deep as the shelter, place a french drain in it, line one of the walls (closest to the house) of the trench with heavy duty plastic and fill the hole with gravel up to within about a foot of the top. Then cut or fold your plastic over the gravel and fill the rest of the hole with dirt. The remaining dirt can be used to increase the slope of the ground away from your house so any surface water will be sloped away.
True, re-read is thread and listen to AB. "WATER ALWAYS WINS" Divert the water BEFORE it gets to your home - do you have gutters and downspouts? How big - deep- is the overhang on your roof above this space? 1st, gutters should have downspouts that move water a mininum of 10-12 feet away from foundation - never into buried sewer lines - AND THEN continue away through slope of your land or french - or other nationality - drain. Soil around the foundation of your house should slope a min of 1/4" per foot for 10-12feet away from house. Eliminate "big bush" fundation plantings that create water channels with their large root system. Along with the backhoe, rent a laser level to maintain a slope to the drain you dig going in the proper direction and min slope per foot.I know it all sounds like a big deal, but just think about it simply. Keep the water away from the house; water will flow the easiest direction with gravity - all you have to do is control these simple facts to your desire. A sump pump is a bandaid.It makes the symptom "feel" better, but it doesnot cure the real problem, control of water.
Thanks for your insight, AB and Rokonmi. This project is beginning to expand in scope. I can't help but feel a bit discouraged. It's costing more and taking much longer than I expected. I wouldn't face these problems if I'd constructed the HSS in an existing basement room rather than expand my crawl space.
It's too late to change now. I've opened a can of worms and so I've got to deal with it.
You may think I'm a nut, but I've decided to not dig a 8 foot deep french drain on the uphill side of my house. There is no "sure" way of routing water from a drain this deep away from the house. Street level is higher than my basement foundation. I could route it into the french drain that runs under the house foundation, but I don't know what capacity that drain has. I don't like the idea of channeling more water *toward" my house to reach this deep french drain.
Instead, I'm hand-digging a shallow (one to two foot deep) french drain to capture and divert surface water (rain and snow melt). I'll also divert all gutter downspouts away from the foundation into this shallow french drain. This water will run out to the street.
None of those steps will stop the current water seepage problem, which I believe is caused by an irrigation ditch that runs along the uphill edge of my property. The ditch is leaking, I suspect. Water is flowing down a hard packed layer of clay that is hard like concrete. I cut through this layer while excavating my crawl space. I can see the water seeping through the soil at the uphill "wall" about 12" above floor level. I estimate a flow of less than 1 gallon per minute. The irrigation ditch only flows from April through October, so there will be a wet/dry cycle annually.
There is an existing french drain running under my house foundation. I plan to lay a connecting drain along this "weeping wall" of dirt and capture the water along the edge of my shelter's floor. It'll run into an existing french drain that runs under the deepest part of the house foundation. I'll have to angle the new drain to stop water from flowing onto my two pillars that support the foundation wall that I'm excavating beneath.
I'm considering adding a third support pillar -- just in case. Also, as a backup, I'll sink a sump that will fill only if the house foundation's existing deep french drain gets overwhelmed or clogged.
Thanks again for your insight. Experience is the hardest teacher -- it gives a test before it teaches the lesson. I can console myself with thoughts like the following, but sometimes I just have to swear a bit.
Kind regards,
TN
Far better to dare mighty things, to win glorious triumphs, though checkered by failure, than to take rank with those poor spirits who live in the gray twilight that knows not victory nor defeat.
-- Theodore Roosevelt
Status Update: All dirt has been removed, leaving a 8'x24'x10' hole where the crawlspace used to be. Dirt is dug away right up to the edge of the foundation wall. The foundation wall is underpinned by three pillars, which each have a 2'x3' concrete footer. The floor was compacted with an electric "jumping jack". Two holes have been dug for sumps. I will have one sump pump operating on 110v and another in the 2nd cistern powered by 12v DC as a backup. Both of these sump pumps will turn on only if the french drain that runs under my house gets overwhelmed or clogged. The sump pumps will eject water into a 1200 gallon plastic cistern. The cister will be the HSS water supply. It will gravity feed back into the crawlspace hole through a hole in my house foundation. The sump water will also be able to route past (not into) the cistern in case the cistern is damaged and I need to get rid of lots of water flowing into the hole.
Last July I had an emergency. Water seeping into my hole from a nearby agricultural ditch started filling it up! The original french drain that runs under my house had become contaminated with mud from my digging. Fortunately I have a friend who does pool servicing and he rushed over with a pool pump and ran a hose to a basement toilet. This kept the water in check. I was out of town on business and had to deal with this problem by phone! Upon my return the next day, I wallowed around in mud and water digging out the contaminated (mud-clogged) drain rock. I replaced it with clean drain rock and the drain is functioning properly. Whew!
I let the project sit idle from July to December because water flowing in from the ditch made it impractical to dig. Mud is not easy to dig. I waited until the ditch was shut off (late October) and the mud dried. In December I built the third and final underpinning column. Two weeks ago I removed the last of the soil and compacted the floor.
A nosy neighbor called the city and they sent a building inspector over. Fortunately I was home and managed to alleviate his concerns without showing him my crawlspace hole. I had planned to have a concrete truck pour the floor, but with the "high alert" regarding building inspectors, I will do the floor by hand. :-(
My next steps are to dig drains leading to the sumps, and order rebar and concrete to pour a strong floor. It will be "slab on grade" and will have rebar reinforcement. It will not have footers (as my shelter is only 8' wide, I thought the floor would be the footer). The floor will have to bear a huge weight (solid walls and concrete roof).
I need to have the floor finished by early April because that's when the agricultural ditch begins flowing again and water will begin seeping into my hole again.
Regards,
True North
I need advice on the thickness of the concrete floor I'll pour (by hand). I had originally intended to do a 8" thick "slab on grade" (no footers) reinforced with rebar. That was when I inteded to have a concrete truck pump it in. Now, due to building inspector concerns, I have decided to do the floor by hand, since a concrete truck will attract too much attention. The thinner I can make the floor, the less manual work required.
Could I safely make the floor 6" thick? 4"? A friend suggested ordering 10,000 PSI "shotcrete" and doing a thinner floor. It would save a lot of labor. If you have experience in this area, please provide advice.
Thanks,
True North
I would strongly suggest going back to the concrete truck idea. You could start by pouring a back patio, and happen to have "extra" concrete on the truck. Otherwise, you are going to run into some major challenges.
1) You will need 95 bags of 80lb quick crete just to pour a 4" floor the size of your room. Each bag only makes 2/3 a cubic foot so each yard of concrete would require 40 +/- bags of quick crete.
2) Trying to mix and pour that many bags of quick crete by hand will take so long that your floor will have a ton of "cold joints". This is where one mixture of concrete sets up before the one next to it is poured. Even if you try to mix them together, you won't get any real strength between the separate pours. Rebar will help, but if you are holding any major load, it will crack at each of these cold joints.
3) Trying to deliver 95 bags of quick crete will show up on at least two palletts, about 5' tall. This will undoubtedly attract the attention of snoopy neighbors.
As far as the thickness of concrete is concerned, you can get away with 4" reinforced with a #4 bar (1/2" dia.) in a 24" on center grid, but you will definitely want to dig a trench in those specific areas where the load will be bearing. Dig those holes at least 4 more inches and run rebar out of them in all directions--spaced much closer together.
A few other tips on pouring concrete:
Curing is the key! Once the concrete sets up (still wet looking but firm), keep it wet. Either by keeping it sprayed down with a mist of water, or add a curing compound to seal it. Letting concrete "dry out" while it sets, will limit the strength below the advertised strength. So instead of 3000 psi concrete, you will end up with 1500 psi, or something like it.
Rebar needs to be placed in the bottom 2/3 of the slab to be effective, but it must have a good inch of concrete below it. Concrete has great compressive strength, but virtually no tensile strength so rebar is added in the bottom half to compensate for concrete's poor tensile strength.
Control joints must be placed in your concrete at specific intervals. When concrete sets, it shrinks at a specific ratio of it's size. These cracks will occur according to the following equation: 2.5 feet apart for every 1 inch of depth. So a 4" thick slab will crack every 10'--thus if you go with a 4" slab, you will need two control joints equally spaced down your room. If you go with an 8" slab, you will still need one, but a 10" slab, you won't. These control joints should be 1/4 the depth of the slab to ensure that your crack follows the intended joint. Once the cracks develop, you can then caulk them with a urethane based caulk to keep most of the moisture out. A little plastic under the rebar mat before you pour would help with moisture as well.
Moral of the story: go with the truck, perhaps even getting someone to pump the concrete for you. Have them set up the pump out at the street and all your neighbors will see is the hose wrapping around the back of your house to pump the concrete for your new patio! You will tell them you prefer pumping it so the concrete truck doesn't damage your driveway. The pump will run you about $350 - if it's anything like we have here, and the pump mix will cost about $10 - $15 more per yard from the plant. It will still be cheaper (yard for yard) than buying individual bags of quickcrete, or portland cement, gravel and sand (if you were to mix it yourself).
As an added bonus, you could pour your patio 12" thick, and then dig out under it as well for some added space to your shelter! If that's an option, I'd be happy to get you some tips for that as well!
Let me know if you have any more questions. I could e-mail you directly if you would like.
Thanks for your advice, AB. I had intended on using a pump truck for the 12" thick roof, which would be absolutely impossible for me to do by hand. At that time, I had intended to pour a slab of concrete at the side of my house. I can't think of a way to justify to nosy people two separate visits by a concrete pump truck -- one for the floor, one for the roof.
How long would it take to do a pump truck pour of 8"x8'x24'? If it's quick, maybe I can manage and then if the issue ever comes up, explain that I'd run into problems with the first attempt and so the pump truck will return at a later date.
I will need quickcrete sacks for doing the walls, so I'd intended to have several pallates of them delivered and "bumped" into my enclosed garage with a forklift. I'd planned to have two electric mixers working in tandem, pouring concrete down a chute through a hole in my basement wall. A wheelbarrow would catch the concrete and I'd dump it. I reckon I'd be able to keep a steady pace that way. Each mixer would have a capacity of 2 or 3 bags at a time.
I've calculated that I'd need 160 sacks to do a "raised floor" which would be a rectangle perimeter footer 10" deep and 16" wide, with the center of the floor thinner at only 4" deep. A duty cycle of 10 minutes per 5 sacks of concrete would require about 6 solid hours of work (for 2 or 3 people).
Thoughts?
Sounds like you've done your homework on the labor. Once concern would be concrete strength. since the ratio of concrete to water generates the strength, had you taken into consideration the mixing conditions to achieve maximum strength?
If you are looking for an excuse to make two pours, you could pour a footing for your patio first, and then come back and pour the slab later. Tell your neighbors that you had to dig below frost line for the footers so that the patio wouldn't move during freeze/thaw cycles and that you would have to separate it into two pours. Play dumb and say that you had a friend in the building industry who "strongly" suggested you would have to make two pours. Then admit your ignorance after the fact saying that you probably didn't have to do it that way after all. Then they will just think that you ended up wasting a lot of money--better you than them.
As far as time it takes to pour the 8" slab--probably less than an hour--depending on your preparation and whether you have to pause for finishing and floating out the slab. There will be another 30 minutes to set up and 30 minutes to an hour to clean up. If you use one of the pull-behind pump/trailers they will probably charge you $65-$75/hour with a four hour minimum, and an additional cost per yard of concrete pumped.
Be careful excavating under your house. The previous owner of my house did it to make room for a FAE heater, and I didn't realize the impact until I tried to obtain approval of addition plans. I had to pay an engineer to design a subterrainean retaining wall, and pay the concrete contractor about double what I would have needed for the addition alone. The rule here is: foundation pillars need a 45deg cone of undisturbed dirt under them, or else a reinforced wall.
The water table is too high around here 9 months out of the year, so underground is not a good option for me. I've read that buried chambers can "float" even with several feet of dirt on top.
I'm leaning toward building a semi-buried "LOTR" root cellar with the door facing away from the city, and grading the fill in that direction. 10'd corrugated pipe would be a quick, reliable shelter if sealed with an epoxy paint, laid in a gravel bed for drainage, and if I can afford it, I'll pour steel-reinforced concrete over the top for neo-eternal durablity. A heavy plastic or rubber sheet between dirt layers should keep things dry (for corrosion), even during the wet part of the year.
AB: I will take your advice. I have decided to use a 2" line pump to get the concrete in quickly. I will pour a pad on the side of my house as well.
ElectRon: The pillars that underpin my foundation wall are resting directly on undisturbed soil. This should be fine. I just hope each pillar's footer is large enough to support the pressure. The original footer (above the pillars) is still 60% supported by the original soil. I will back-fill the void around the supporting pillars to prevent their soil cavity walls from caving in when the wet season starts. The soil gets softer when wet. My intention is to put a layer of drain rock or pea gravel between these soil walls and the cinderblock walls of my room.
This weekend I put in a 1200 gal. poly water cistern (Norwesco). Once I've completely back-filled with a sand/grave mix, I'll put a 1 1/2" layer of styrofoam board for extra insulation, then top it off with 12" of soil.
I have scheduled my concrete floor pour for early May (when some nosy neighbors will be away on vacation). I have about a month to finish preparing the excavated crawl space. I have to make a decision: Do I pour the concrete directly onto the wet soil, or should I put in a layer of gravel first?
Background:
I've built perimiter drains along the two earthern walls that experience water seepage. Those drains route water to two sumps, which overflow into the house's existing french drain. The sump pumps will turn on only if the main house drain clogs or gets overwhelmed. I can lower the pumps if I want to capture the water the flows into the sumps. (The sumps are connected to a coil of "flex pipe" which enables them to be raised and lowered without reconnecting plumbing.) Currently I'm seeing about a gallon every five minutes, which works out to be a bit less than 300 gallons per day.
The perimiter drain catches some of the water, but not all of it. The dirt floor has turned muddy during the "wet season" (an irrigation ditch flows near my house seven months per year). Will it be OK for me to pour concrete on a floor that gets muddy for about half the year? During the dry season I compacted the floor with a jumping jack.
I want to avoid mould developing in the future, so I plan to pour the concrete slab on a sheet of 10mil plastic, which will be pulled up on the sides to keep the concrete dry.
My question: Should I put down a layer (3" ???) of pea gravel below the plastic? The advantage would be a non-wicking separation of the wet soil and the concrete. The disadvantage is the cost and the effort, and yet another pile of building materials in my driveway to arouse the curiosity of my neighbors. Do you think a layer (or two) of 10mil plastic will be sufficient, or would you put down the gravel too? Remember, I have perimiter drains which will prevent the water level from rising above the floor level.
Opinions welcome.
I am not a cement contractor, nor do I play one on TV, but I've had cement jobs done at my house. Generally, all the cement contractors say pour on at least 4 inches of pea gravel and you'll have fewer cracking and settling problems. I don't know how that will work with your water problems.
I would suggest that it would depend upon the type of soil under your slab. A highly expansive soil that would have a tendancy to expand or shrink depending upon the moisture level virtually requires gravel underneath. It will help dampen the effects of uneven swelling.
If you are confident that the soil we remain dry and compact, then you can get by with just laying down some plastic. The stronger the concrete, the more resistant to leakage.
Either way, you should invest in a dehumidifier, and provide some kind of drain in your slab that will allow the condensation to drain into your sump system.
Sounds like you have things pretty much figured out. Good luck!
Thanks Darrell and AB for your thoughts.
Regarding moisture: The soil under the slab will get very wet for 7 months each year. (Despite my perimiter drains, right now the top few inches of soil on which the pad will sit is is gooey mud.) The remaining 5 months of the year enable it to dry out. This annual wet/dry cycle is caused by an irrigation ditch near my house. When the mud dries it does crack, so that tells me it does have some expansiveness.
I'm planning to put down eight inches of concrete, so this will be nice and strong. Hopefully concrete 8" thick will not crack.
I plan to lay two runs of rebar along the perimiter of the 24'x8' slab. Do you think I should have some lateral (8') rebar reinforcing too? I will put down wire mesh before I pour the floor.
My thought was to have the lateral rebar bent upward at both ends so that it would project above the floor level. This would enable me to build my cinderblock walls directly on this rebar. This would securely tie the walls to the floor. I want the walls to be able to resist some lateral pressure in case of earthquake (where the earthern walls might liquify and push sideways).
The wire 6x6x10 mesh I assume you are planning on using really won't be very beneficial. It has to be elevated off the floor about 1/3 the thickness of your slab and is only designed to help keep the concrete together when it cracks. It does little to add structural strength. Instead, I would suggest going with a fiber-mesh additive to the concrete mix. This will give you added strength, for a fraction of the cost and effort of the wire mesh.
I would definitely go with the rebar bent up into the walls. Don't go too high 8"-16", or it will be too tough getting the blocks over them. Simply add sections of re-bar as you go and "tie" them into each other by filling the cells with mortar or concrete.
Due to the expansiveness of the soil, it probably wouldn't hurt to add some lateral rebar (perhaps 24" o.c.) accross the slab. Going with rebar under your future masonry wall is definitely a good idea. Again, for it to be effective, elevate it about 1 1/2" above the bottom of the concrete to maximize its effectiveness.
I have a concrete footer / wall design problem that I hope you can help with. (Time is short -- my concrete is scheduled for Friday and I'm building my forms now.)
I have a very narrow room, 8' wide x 22' long, that I need to pour a floor pad and footer for. Unfortunately, because of some water problems, I have a perimiter drain along two of the edges. I don't want to put the footer on top of this drain. So... I need to put the footer next to the drain, which narrows the floor to 7' instead of 8'. Once the 6" cinder block walls are built, the room's interior width shrinks further to 6'. Inches count a lot in a room this narrow.
Is there a safe way to build the wall up a foot, then slope it outward a foot, then upward again? This would ensure that direct pressure did not push down onto the drain. My concern is that the concrete wall wall not be strong if I angle it horizontally, since the heavy 1' thick concrete roof will be bearing on it.
One idea is to slope an integral floor/wall pour outward at a 45 degree angle for one foot and reinforce it with rebar. I have never done any concrete work before, so I need guidance on the viability of this plan.
a. Can a short vertical wall be poured at the same time as a floor pad? If the concrete is runny, I expect it'll slump out of the wall form into the area of the floor.
b. Could I do this angled upward projection later, after the floor pad has cured?
c. How much rebar reinforcement would be necessary to give the sloping wall the strength it needs to withstand the cantilever forces?
Comments gratefully accepted. (My plan is to get the forms finished and rebar bent tomorrow.)
Regards,
TN
It would almost be better to fill in your drain area with gravel and pour right over the top of it. The gravel will give sufficient bearing, and then tie re-bar to help hold it together.
Another option might be to isolate the bearing of the ceiling from the concrete walls--by extending the ceiling beyond the walls, beyond the drain area, and onto solid bearing. Without seeing it, I can't tell for sure if this will work, but it's probably better than trying to carry the cantilever forces you will be dealing with. Otherwise, you would have to get an engineer to calculate a proper design. You will be carrying about 1500 lbs per lineal foot of wall on both sides--just in concrete.
If you do wish to pour it all in one day, it is definitely possible, but with a pump, it becomes much more difficult. I would suggest pouring the bottom edge of the "step" area, and then pour the rest of the floor. Wait as long as you can for the bottom concrete to set up a bit, and then pour the top step. This will be difficult because you will have to walk back over your poured concrete to get to it, but you will be able to work out the footprints when you "float" the surface.
Good luck! If in doubt, delay the pour. It's much easier to reschedule a pour then it is to repair a collapsing concrete wall!
I'm glad you're on the net tonight, AB! Thanks for the advice. I feel a lot more comfortable tackling a new project like this with guidance from folks like you and others on this forum.
If I fill in my drain area with gravel and pour on top of it, the floor will only be four inches thick over the drain. I had planned a 9" deep footer around the perimiter of a 6" deep slab. I'm concerned that 4" will not be thick enough to support the wall and roof weight.
I cannot raise the footer's base to pour over the the top of my perimiter drain because I have headroom limitations.
At this point I've resigned myself to building a narrow room and hoping I'll never have to spend much time in it. :-|
Even though I'll likely pour the narrower floor tomorrow (7' edge to edge, outside dimension) I'll have #4 rebar projecting upward every few feet, so that will give me the option of pouring some a sloping cantilever as a next step after the floor cures. Still, I like the idea of keeping things safe and simple.
Oh, I read today that putting plastic sheeting under a poured slab weakens the surface, since all the moisture has to escape upwards. I have a wet floor area and intend to use plastic sheeting to minimize water wicking... but I don't want to weaken my structure.
I have ordered 4000 PSI concrete, 3/8ths" pea gravel (to fit in a 2" pump line) and fibermesh (as you suggested). 4 inch slump. Does that seem reasonable? The same mix will be used to pour a 4" slab outdoors too... as justification for having a concrete truck pay us a visit.
I'll check this forum tomorrow (Wednesday) morning before I build the forms in case someone has a flash of compelling inspiration.
Thanks again for your ideas.
TN
First of all, the issue with bearing on the 4" slab. You're probably right about it not being thick enough, however, if you step up your slab on top of the drain line and add several rows of rebar (in addition to some rebar tying it into the slab portion) then you could probably get by just fine with having your walls bearing on top of the gravel-filled drain line with 8" of concrete on top.
As far as the plastic goes, it could weaken your surface if you pour "wet" concrete. Meaning that most finishers like to add water to the concrete when it shows up on site to make it easier to work with. Since that water isn't needed to react with the cement, it basically has to go somewhere and eventually it seeps up to the top--thus weakening your surface. As long as you don't add water to the mix when the truck shows up, then plastic shouldn't affect your stregth in any perceptible amount. Instead of adding water, have them use a "super-plasticizer" to allow for pumpability (they may already do this if you specify "pump mix" but check with your supplier). This ionizes the mix to make it flow easier (for a couple hours only) without adding water and reducing the water/cement ratio.
I'm assuming you've already checked with your pump man and he can pump a 4" slump with his 2" line.
The perimiter drain has a 3" perforated PVC pipe close to the surface. (It's a very shallow drain.) The pipe will have some "give", and so I'm certain that the drain won't bear weight well.
Thanks for the reminder to check if the 2" line pump can handle a 4" slump. I just called him and he said that a 4" slump is OK for the distance we'll be pumping.
The concrete company said they'd be delivering 708414 mix. I don't know what that means. Do you?
Once the concrete sets, it will "bridge" your drain. If you run a piece of rebar across your 3" pipe every 16" or so, plus a couple pieces running lengthwise with the drain, the load will be transferred to the bearing area on either side. As long as it's a uniform load across the length of the pipe, you should be fine.
If you really want the space, I don't think pouring over the top of the drain would a really present a problem. We bury plumbing drain lines under concrete all the time with no real adverse effects.
As far as the pump mix number is, I couldn't tell you. Down here they specify by the different ingredients and ratios, I'm not familiar with the numbering of mixes. It might be something specific to your supplier.
Thank you for your advice. My flurry of activity is over... for now. The floor was levelled. Pipes connected (sump pumps, etc.) A layer of drain rock tamped. Forms built. A liner of 10 mil plastic placed. Rebar cut and bent and tied.
Then in a mad scramble, on the day of delivery, I prepared a form for a pad on the side of my house. The line pump truck arrived, then the concrete arrived. Two friends and I poured the interior, then did the exterior pad. We timed the pour for mid-afternoon to minimize the number of neighbors who'd see the concrete trucks. All went well... until the rain and snow.
After the exterior pour completed, rain started to fall. We covered the exterior pour with a sheet of plastic and waited for the rain to stop. It didn't. Instead, it turned to snow.
We did our best to level it with a bull float, then we covered it up and insulated it well to prevent it from freezing and cracking. Better to have an ugly strong slab than an ugly weak one.
When I pulled the plastic off the next day, I saw an ugly scarred surface. Oh well, at least it's in an inconspicuous location.
I've been wetting down the interior slab three times a day by pouring water on it... to slow the cure. I intend to do this for a week, then let it dry. Is that about right?
Finishing the interior slab took a lot longer than we expected. The 9" slab was poured into a basin of plastic film. This meant that it stayed wet for longer and took longer to "fire" or set before it could be hand trowelled. Normally a 2" layer of damp sand should be placed on the plastic film. I didn't have time or space or energy to use the sand.
It's all worked out well. No inspectors. No visits from the neighbors. The hole in my crawl space certainly looks a lot more orderly now that a clean crisp floor is down. In a day or two I'll cut a 2" line across the middle of the 7'x22' floor as an expansion joint.
I'll be taking a break from this project for a while. It's time to rebuild relationships with my family.
Again, thanks for the coaching, folks. It's nice to have you around.
TN
How are things with your crawl space shelter? I am thinking about doing something like you did, but I would like to know how you did your ceiling/roof of the shelter. Did you do it like Joel recommends in his book (the filled cinderblock method)?
Hello Gang,
I've been off my project for some months now, but will be getting back into it after the Christmas holidays.
Darrell, I plan to build the walls this winter/spring, then pour a 10 or 12" reinforced ceiling sometime mid-2004. (I don't have the room to use Joel's filled-cinder-block method for my roof -- my existing foundation walls are too close -- not enough space to work.
I have a seasonal irrigation ditch nearby that saturates my property, so I've waited to verify that my water drainage solution worked before I sealed up the crawlspace by building walls. I've been measuring and plotting the water flow rates for almost a year now, and things have stayed manageable. (Peaked in late October at 2750 gallons per day, about 2 gallons per minute.) I'm comfortable putting up the walls now that the water drainage test has been passed. The water seepage has it's benefits, though. I can fill my 1000 gallon cistern with it. Next year I may connect a pump to my irrigation sprinklers and use it to sprinkle my lawn.
In retrospect, I should have built the HSS in the spare basement bedroom of my house. Digging out the crawlspace was A LOT of work. It also attracted the attention of my neighbors. "Where's all that dirt coming from? Four dumpsters full?" I even had to deal with a nosy building inspector. That's enough stress for me.
I developed a bit of wrist trouble from all the digging and bucket hauling. The vigorous work aggrivated an old injury. If you decide to dig out your crawl space, be prepared for a lot of work.
Also check to make sure you have good non-expansive soil. A friend of mine says that I'm really lucky that my house is built on good soil. He sees a lot of bentonite around here, which can cause shifting.
I have noticed a few minor cracks appear in some parts of my house. I use a rotating laser level several times a year, and my crawl space excavation and footer underpinning has caused one side of my house to drop about 1/4". This is probably due to the drying of the soil walls -- the soil shrinks and cracks as it dries.
That's the update for now.
Cheers,
True North
Update: I have resumed work on my crawlspace HSS project. About a year has elapsed since I poured the floor (in a tub of 10 mil plastic sheeting to provide water protection). Despite the wet soil conditions, the concrete has remained perfectly dry. As you may remember from earlier posts, water flows through my excavation for about 8 months of the year. I have monitored the water flow. For your interest, here are some data points from 2003 (gallons / day, measured at end of each month):
Jan: 0
Feb: 0
Mar: 168
Apr: 1120 (irrigation ditch starts flowing)
May: 1260
Jun: 1440
Jul: 1938
Oct: 2400
Nov: 286 (irrigation ditch stops flowing)
Dec: 0
The 2004 flow rates are similar (so far).
A perimiter drain around the edge of the concrete floor slab routes the flow into and then out of two sumps (set into concrete below the water level). These shallow wells are rigged with sump pumps in case the outflow (to the french drain under the house) clogs. I've had a year to observe the proper functioning of this drain system and am confident with it... so now I can begin constructing the walls.
Because my room is very narrow, I will be extending the width of the floor by building an 8" high step along two ajoining walls, which will increase the width about 8", which leaves me with an inside width of 6.5'. I needed to find a way to reinforce this "step" for several reasons:
• Concrete has poor cantilever strength
• It will be rest on flexible perforated pipe covered with drain rock (not a stable, load-bearing foundation)
• It will support very heavy loads (solid 6" concrete walls, 12" poured concrete roof, and rebar
In addition to #4 rebar at 8" OC, I have some short segments of 6" I-beam projecting over the lip of the floor to add cantilever strength. These I-beam segments are bolted over the existing floor's rebar-reinforced footer. These I-beam segments will be cast right into the 8" step and are spaced about 4' apart. Although this I-beam idea has not been designed by an engineer, I'm hoping they will transfer load from the cantilever step to the stable floor. (I should have taken the time to build this "step" a year ago and poured it integral to the floor, but I was rushed and stressed. So now I'm playing catch up.)
A friend suggested I increase the strength and waterproofness of the concrete step by paining the existing concrete with a milky latex bonding agent before I pour the step.
So, for the next few days I will be:
• Building the framework for the cantilever "step" to widen my room. (Bend rebar, tie rebar, build wooden forms.)
• Waterproof the excavation walls by hanging 2 ply 10 mil plastic sheeting over the dirt walls (which will touch the cinder-block walls I'll be building soon).
Any thoughts whether the 2 layers of 10 mil plastic will be sufficient for solving the dampness problem? It's worked well for the poured floor.
Regards,
True North
HSS construction project update: I finished building and filling the reinforced cinderblock walls of my HSS. The walls have four low 3" PVC pipe ventilation holes and four high 3" ventilation holes at the other end of the HSS at ceiling level.
I then poured the concrete roof. It is 10" thick and is very well reinforced:
#5 rebar every 8" in the narrow direction (7' wide)
#4 rebar every 16" in the long direction (22' long)
2" thick steel bar every 6' in the narrow direction
Joel recommends a 12" thick concrete roof. My roof is 10" thick. I hope that 10" of poured concrete will provide about as much radiation protection as a 12" (less dense) concrete-filled-cinderblock roof (as described in Joel's HSS construction guide). My long term food supply will be stored above my 10" thick roof, providing some extra mass to augment the 10" thick concrete's radiation shielding.
Last night I tore down the forms that supported the concrete pour. Now I'll begin the outfitting of the interior.
First, I'll start by painting the interior cinderblock and ceiling with a latex masonry sealer.
Next, I will use my recycled 2x4s and plywood to build a vented 12v battery storage cabinet, a work bench, a utility countertop with sink, and 4' wide triple bunk beds which will serve as shelving.
I will begin learning about 12v electrical systems for charging my 12 12v batteries. My plan is to trickle charge them from my 120v mains. Later I may put in some solar panels, but not now. (I will use efficient fluorescent or LED lighting. Recently I stayed a in a pop-up camper which was lit by 12v incandescent lamps, and the battery was drained in 4 nights!)
I will also find some hardened steel plate to armor the steel utility door.
Several years ago I hung three layers of 10 mil plastic as a moisture barrier between the dirt wall and my HSS cinderblock wall. This plastic was anchored underneath the HSS concrete floor, which is ringed with a perimiter drain. I am happy to report that I have had no dampness at all. The concrete floor developed a few hairline cracks during the wall construction, but the cracks have not worsened after the heavy (25,000 lb) roof was poured.
Lesson learned: Order 1/2 yard more concrete than you think you will need.
Another lesson learned: Specify a 2" line pump if your concrete pour is indoors and is awkward to reach. I was horrified to see that a concrete boom truck arrived with 4" pipe, which was very heavy and awkward to work with in cramped quarters. The boom truck was very visible to neighbors. The trailored 2" line pump (for 3/8" pea gravel concrete mix) that I used for my floor/footer pour was much "lower profile" than a boom truck.
Congratulations on getting the "protection" portion of the shelter finished. This has been a long project and you have endured to the end!
Now all you have to do is augment the "protection" side with the "survival" side and you'll be all set. Let's just hope you never have to use it.