Hi Tim,
I've read a lot of the articles you have on your website regarding basement construction. We are going to go with a concrete block wall, reinforced with rebar and poured solid. But, my question to you is, for the main basement wall that runs horizontally from the left to the right side of the house, what factors determine if 8" or 12" blocks are adequate. We will have a crawl space in the front half of the house so the dirt will not come up but to about half of the way up the front side of the wall. I was told at a local architectural firm here that the 12" blocks are overkill and that the strength of the wall will come from the rebar and the concrete the blocks are filled with. What are your recommendations?
Sincerely,
Leigh
Valdosta, GA
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Leigh,
The wall thickness is a function of the wall height and more importantly how much backfill height is on the other side. For example, let's say the foundation wall is 9 feet but outside you will have 3 feet of foundation exposed because you are duplicating a 1920's Craftsman style home. Since there is only 5 to 6 feet of backfill pressing against the wall, you may get by with an 8 inch thick block. But what happens if there is 8' 6" of fill against the 9 foot high wall? The pressure grows exponentially. You then may need a 10 or 12 inch thick wall.
Don't play a guessing game here. Hire a residential structural engineer and let him do a proper wall design. Be sure the contractor follows the plan to the letter.
Tim Carter
www.askthebuilder.com
W3ATB