Is a foundation really that important? The answer to the question is yes! As far as I’m concerned, it’s the most important part of a building to ensure its long term survival. If the foundation crumbles, shifts or isn’t square and level, the poor building set upon the inadequate foundation is headed for a lifetime of misery. Surely you’ve seen pictures of the leaning tower of pizza. 🙂 I mean Pisa. Is a foundation really that important? It is paramount!
We’ve built 2 of our off-grid homes and are currently working on our third. Each home has had a different foundation. Let me briefly describe the first 2 and then we’ll delve into the specifics of our current foundation construction.
My First Construction Experience in Maine
Maine was my first building experience going on 38 years ago. I was young and clueless. I had no building experience and learned on the fly. The house had concrete piers as the foundation. With the help of my Dad, we dug down to bedrock, built wooden forms and then by hand, mixed the concrete in a wheelbarrow and poured the concrete into the forms.
Although we dug down to bedrock, during cold snaps in winter, the building did shift. The frost heaved up the concrete piers. The shifting affected the opening and closing of a picture window until frost came out of the ground.
When we moved to the Saskatchewan wilderness, we had a different scenario to deal with. Sand! This was a fly in location only. No chance to bring in any construction equipment. We chose a sandy knoll on which to build. By hand, we dug a level trench around the perimeter of the house. We were careful not to disturb any soil below the trench level.
We hand sifted gravel from the material we dug out of the trench. After putting a layer of this sifted gravel back in the trench, we laid pressure treated 2 X 10 flat on the gravel to act as our footings. Then we built a 24” knee wall out of pressure treated lumber, back filled and built the remainder of the house as usual. The house never shifted whatsoever. As a testament to this, I had several dish antennas mounted on the house and they never needed re-pointing.
The great thing about pure sand is it doesn’t hold water. The grains themselves get damp but there’s not enough water retained to freeze and expand to cause problems. As a result, the house was rock solid.
ICF Building Forms for Our Last Homestead
Now that we’ve moved to Nova Scotia, we are dealing with our third foundation. A foundation that required an excavator to dig out a large cellar hole. This will be our first experience with a basement. Our choice of home construction is ICF. (insulated concrete forms) I am in unfamiliar territory with the foundation and ICF construction so this will be a learning experience.
We had planned on building another super insulated home modeled after our Saskatchewan wilderness home. That house had 10 inch thick walls with a good vapor barrier which made for a toasty dwelling regardless of how absurdly cold the temperature was. -57F was our coldest temperature but it was easy to stay warm that day with our wood stove.
ICF construction came to my attention while I was doing some research and it piqued my interest. Especially since we are building literally 150 feet from the ocean where we will be subject to gale winds and without a doubt, a hurricane down the road. Having a house built of reinforced concrete sounds pretty good.
We will build the house with ICF forms. These forms are made of two parallel pieces of 2 5/8” blue board foam. Keep in mind, 1” of blue board equals R-5 insulation value. So the blue board form automatically gives us approximately R-26 of insulation value. These pieces of blue board are held parallel to each other via a plastic web placed 8 inch on centers. There is an embedded plastic screwing surface also on 8 inch centers which gives us an easy way to screw interior and exterior finishes.
Our choice of concrete thickness is 6”. Between the blue board and the concrete, ICF manufacturers claim we can attain an insulation value of roughly R 40 to 50. You can read about it here. http://www.nudura.com/divisions/home-owner/thermal-mass But the gist of the idea is the concrete is an enormous amount of mass. That mass heats and cools slowly, especially when it is sandwiched between 2 blue board layers. That creates an effective wall insulation value much higher than one might have thought possible.
So we will have an insulated concrete wall with high insulation value. On top of that, the blue board is also the vapor barrier. This technology solves a number of problems in one fell swoop. I will of course update you all on the house construction itself once we build.
Because of the mass of these concrete walls, the foundation needs to be designed to not only handle the weight of the concrete structure along with the house contents, but also needs to have a way to lock the wall to the foundation. In our case, I built wooden forms for the concrete that would give us a 20“ wide X 10” deep concrete footing. I used 2” X 10’” lumber.
Building Our Footing Forms
The forms consisted of two parallel 2 X 10’s spaced 20 inches apart on the inside dimensions. I cut 1 X 3 boards about 28 inches long to span across the forms as spreaders. They were temporarily nailed roughly every 3-4 feet apart down the length of the forms. Their purpose was to keep the forms true to a spacing of 20 inches even after they were filled with concrete. Without them, the forms would likely bulge.
I watched a few youtube videos on wooden form construction that were supposedly professionally done by contractors. Their finished product was anything but straight. I guess in the long run, that’s fine, but having true, straight forms properly leveled gave me peace of mind and can’t hurt when the building inspector shows up to take a peek at things. Once he sees you are serious about doing a quality job, I think he/she will be far more likely to help out as best they can. Furthermore, beginning construction with footings that are straight, level and square will also make for an easier time with less aggravation and frustration.
The excavator dug out the hole and using a laser transit, got us close to the proper depth. But some areas needed some fine tuning and it was tough digging. Johanna and I struggled for hours digging down a few inches along the length of a side. The earth we were digging out was essentially gravel with small embedded boulders. It was like digging packed cement. A pick ax and long pry bar were essential digging tools.
After the hole was dug out to the proper depth, I built the form around the perimeter of the building. (I did have a few hours of help from a couple of friends) To make sure it was straight and square I placed nails at the corners and ran string. That gave me a good idea of how straight the form was. It didn’t need to be perfect but my pride wouldn’t allow something that looked like it was laid out by a drunken sailor either.
I took a 100’ tape measure and measured the diagonals from corner to opposite corner. Those 2 measurements told me how square my footing was. If the diagonals were not equal, I knew I had a parallelogram. To rectify this, I took a sledge hammer and tapped a corner that formed the longest diagonal measurement and moved a whole side an inch or so and took new measurements. I repeated the process until both diagonal measurements were equal. At that point I knew I had a square foundation.
While the transit was available, I was able to level a section of the form. But because the contractor owned the transit, once he departed, I was left with the daunting task of leveling the entire form to ideally within ¼: I did even better than that and got it to within plus/minus 3 inches!
Of course I jest. That would be a disaster to be out by that much. It took me several days with my good 4 foot carpenter’s level and a straight 2 X 10 to painstakingly level a small section at a time. I worked my way around the perimeter and was pleasantly surprised when I got to the end and saw I was very close to perfect.
I also had to level across the forms. What I was ultimately trying to do was create a perfectly flat platform in all directions. I bought several bundles of stakes for the purpose of leveling my forms. I started my nails in the stake and drove the stake in with a sledge hammer next to my 2 X 10 form. Instead of trying to use brute force to lift a section of form that needed leveling while trying to nail my stake to the form, I employed my pick mattock to raise the form with one hand while pounding the nails home on the stake. The pick mattock has a curved blade and long handle which is perfectly suited for the leverage I needed to lift the form by myself.
Johanna followed behind me and shoveled dirt along the bottom of the forms on the outside. That dirt closed all gaps between form and the ground and created a seal to prevent the concrete from flowing out after it was poured.
Once I had my forms built and level, the last step I needed to do was give them some reinforcement. I used my 1 X 3 cross braces to hang 20’ long lengths of roughly 7/16” rebar. I hung 2 pieces of rebar parallel to each other around the entire perimeter. I used utility wire to hang them from the cross braces. At the corners, I bent the radius by hand. Any overlaps were wired together with at least 24 inches overlapping.
Site Preparation and Concrete Work
I prepared the site for concrete delivery by picking up and piling all rocks in the basement area that would impede a heavy wheel barrow filled with concrete. I raked paths as smooth as possible. I lugged 4 sheets of plywood down into the hole to give a smoother surface to facilitate wheelbarrow maneuverability. “Normal” concrete has a finite life before it starts to harden and cure so time is of the essence. Anything I could do to prepare the site to get the concrete from the truck to the forms as fast as possible, I did.
I had a form that ran across the basement that would be a partition wall and that created a problem. I would either have to build a ramp over it so that we could take wheel barrows across or I would somehow need to build a bridge. I opted for a bridge.
I built 2 rugged stands out of spruce/fir trees. One stand was about 5 feet high, the other 3 feet high. I used my good aluminum ladder and lashed it across those two stands to create a sloped ramp. Then I took 3 pieces of 2” X 10” X 16’ and built a “U” frame. That “U” frame was lashed down to the top of the ladder and formed a long 16 foot sloped trough. The last thing I did with my trough was to line it with a piece of sheet metal. The local building center had sheet metal in 8 foot lengths. I was able to take the sheet metal and form a “U” that fit inside the wooden trough. A couple small nails held it in place.
This was a big experiment and I had no idea how this would work. What I was trying to do was have the concrete truck back into a stationary position as close as possible to the foundation hole. The concrete truck could reach about 17 feet with its onboard discharge trays. With my home built trough, I extended its reach another 16 feet, hopefully eliminating much wheelbarrowing of concrete.
I used an online concrete estimator, added a half yard fudge factor and placed my order for 3500 PSI concrete which is more than what is needed for structural strength of the footing. Because most of the concrete would need to be wheelbarrowed into the forms, I hired an experienced crew to help me. The cement truck backed in, reached out to my waiting metal lined extension trough and the concrete flowed down the chutes from the cement truck to our waiting wheelbarrows.
My set up worked like a charm! We had 3 wheelbarrows going in assembly line fashion moving concrete to the waiting forms. The process went like clockwork.
The guys commented on how well prepared we were. I had taken a big risk with my homemade trough since my new burly friends might have fit me with new “concrete shoes” if my handiwork had failed!
Once all the concrete was in the forms, it was time to level and smooth the top of the concrete flush with the top of the forms. We used a short piece of 2 X 4 to quickly level the concrete to the top of the forms and then used trowels to smooth the surface for a professional look.
The last step was to set 30” long pieces of 5/8” rebar vertically every 3 feet on center around the perimeter of the house. I set them in the concrete 10” with 20” remaining above the concrete surface. Technically, they only needed to be set in every 4 feet but I over engineer and went 3 foot on center. The purpose of this rebar is to lock into the walls that we will soon be erecting.
After the concrete set for a few days, all the forms were carefully removed. For safety all nails were removed from the lumber and then the lumber was stacked for reuse. I took the time to clean up all the lumber and stack it level so it shouldn’t warp. Then I took a couple of watering cans filled with well water and several times each day, sprinkled water on the concrete footings to slow the rate of drying. If the concrete dries too fast, there can potentially be a problem with shrinkage and loss of strength. Here is a good explanation for concrete curing.http://www.ce.memphis.edu/1101/notes/concrete/PCA_manual/Chap12.pdf
A Few More Details
This gives you a good sense of what we did for our house foundation. Here’s a few remaining thoughts for you. We asked the excavator operator to skim off the top soil before he started digging in earnest. That top soil will be utilized in the garden as well as landscaping around the house.
Concrete is caustic and can cause burns. Consider wearing safety glasses since it constantly splatters when flowing into the wheelbarrows. Wash all tools as soon as work is done since they will be hard to clean once the concrete hardens. Wash any exposed skin as soon as work is done or you risk chemical burns.
Finally, we had 2 concrete trucks come in with partial loads. Unbeknownst to me, the second load had a retarder added. I was some excited the next morning when part of my footing was still soft. I called the concrete company who assured me it would all set up just fine by the end of the day. And sure enough, the material set up as hard as “concrete.”
Until next time, keep the dream alive! We wish you a great day!
Ron and Johanna
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