Questions about Footings and Foundations
with replies by Thomas J. Elpel

Questions:

• How do I deal with bedrock when pouring a footing?
• Is it okay to have cold joints in the foundation?
• How can I pour a foundation on a budget?

Questions Policy
      To avoid re-writing my book Living Homes for every person that comes along, please read the book before you write to me. Then, if you have any questions beyond what is presented in the text, then yes, please do write and ask away! I may be a little slow to answer, since I have more than a few distractions, but I will get back to you in time, and I will answer your question to the best of my abilities. Please let me know if I can post your letter and name to the website. Thanks!

      Also, if you have a better answer to a question than I do, or additional useful information, then please send me a note through our E-mail Contact Page, and I'll add your commentary to the web page. Questions and answers on these pages will help guide revisions of future editions of Living Homes.

How do I deal with bedrock when pouring a footing?

Hello Thomas,
      Thank you for all your efforts to "green" our lives and reconnect us to sustainability. I am building a house in Nova Scotia and am an active participant in the process. One potential builder likes my idea of using slipform, at least for the foundation and for the chimney. We are working on the design so there many be more slipform used. Here is my question:

      I am building on very rough terrain with some bedrock... and only about a foot of soil above the bedrock. Do you have any advice about how to build in such terrain and make the slip form wall continuous? A picture is worth a thousand words.

      Thanks you for your help. I hope these questions are clearly stated and make sense.

Looking for a more sustainable future,

Dawne

Dawne,
      Will you be contracting out all of the work or doing some of it yourself? A hand-crafted home can be quite a bit more expensive if you a) use all new materials and b) hire someone else to do it. In regards to your question:

      My brother's house is built into the hill with part of it on bedrock. He excavated down as much as he could, then decided that bedrock was as good a footing as one could ever hope for, drilled holes into the rock for rebar, and went on up with his walls. So, it could potentially save some cash to utilize the bedrock as your footing, depending on how even it is across the site.

      As far as "green" and sustainable, keep in mind that there is nothing environmentally friendly about bulldozing a pristine environment to build a house. Build within an existing community to be truly green. Also, cement is highly energy intensive to produce and is a major contributor to global warming. It is only "green" if the house is designed and insulated to nearly or entirely negate the need for fossil fuel heating. Utilizing secondhand materials in the building process also helps.

      I hope this info helps. Keep me posted.

Sincerely,

Thomas J. Elpel

Is it okay to have cold joints in the foundation?

Hello Thomas,
      I have a couple more questions. I am intending to use slipform for a foundation for a frame building. These are actually questions from my 89 year old father who is a carpenter:

      1. The use of 18-inch to 2-foot slipforms results in horizontal "seams" in the cement. I know there is rebar but don't these horizontal seams result in a weaker foundation?

      2. If one cannot complete the entire circumference in one day there will be vertical seams as well. Will this cause a problem for a slipform foundation?

      3. How does one make strong corners?

      4. How do you finish the top of the wall to start your frame building?

      Thank you for all your help.

Cheers,

Dawne

Dawne,

      Nice to hear from you again. In answer to your questions:

      1 & 2. Yes, every horizontal or vertical "seam" is a "cold joint," which is not as strong as pouring a wall all in one unit. Cold joints are impossible to avoid in slipform stone masonry, but its okay, too. It is a difference between "stronger" versus "strong enough." When we finish filling a set of forms, we add enough cement to lock down the top layer of rocks, with the concrete sloping outwards (so that water won't follow the cold joint inwards), then use our gloved hands to poke holes in all along the top to "key" the wall in with the next pour. Vertical seams should taper diagonally, or better yet, try to end at a door or window opening, to avoid the vertical seams. You can also add as much rebar (or old cables and other scrap metal) as you want to better tie the sections together.

      3. Be sure to bend the horizontal rebar around the corners. That will make the concrete strong. Brick-lay the rocks, alternating the overlap from each side as you go up. That will make strong stonework.

      4. Do you have Living Homes? Ordinarily, a slipform stone wall is finished just like a concrete wall: Mortar L-shaped anchor bolts in the top layer, then bolt a 2 x to the top of the wall, typically with tar paper, fiberglass insulation, or some other barrier between the wood and the cement work. Then attach the roof to this "sill plate."

      Do keep me posted on your progress!

Sincerely,

Thomas J. Elpel

How can I pour a foundation on a budget?

Dear Thomas,

      I came across your website and plan to buy at least one of the books listed there. I am building my house on very limited means, and the Living Homes seems perfect.

      I have spoken to many people and done a significant amount of research on low cost foundations. Where I live, in upstate New York, we have harsh winters, and I have searched for a low cost way to put in a foundation. As it is, I have around $5,000 to begin building, and the foundation alone, as suggested by everyone around me will cost $4,000 minimum to pour concrete 4 feet down to the frost line...

      Any ideas? How did you do the foundation of the house in the front page article with such limited means?

      I appreciate your time, efforts, and assistance.

Thanks,

Elan

Elan,

      Thanks for your letter and your order. The book will ship out today.

      A few possibilities, as described in Living Homes:

1) You might consider a rubble trench to get down four feet.
2) Or an insulated footing to avoid going down four feet.
3) Or dig down four feet, and design the house so that it starts four feet underground.
4) Same as above, but do slipform stone masonry to reduce the concrete cost.

      Our own place is dug into the side of the hill, which makes the footing ten feet below grade in the back. It is insulated across the front of the house. It was started and abandoned by a previous owner. We bought the property and adapted our plans to fit what was already here... so we didn't have to pour a footing at all. Nevertheless, I think you will find the info in Living Homes to be very helpful.

Sincerely,

Thomas J. Elpel

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