Concrete block construction questions.
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Building a single story home in Alabama that will be framed 2×4 but also has a basement foundation built of concrete blocks. Because of the slope of the lot I expect ot have as many as 13 courses of blocks on the back and center walls (it’s actually a half basement). My questions are:
1. At what height must the top or all of a concrete block wall be poured solid?
2. Do I still have to pour the wall if I use a bond beam like they do in Florida on homes built with block construction?
3. In areas that experience colder temperatures as well as humidity, are concrete block homes more or less likely to have mold or moisture problems than wood framed homes?
Replies
Greetings jcrew,
This post, in response to your question, will bump the thread through the 'recent discussion' listing again which will increase it's viewing.
Perhaps it will catch someone's attention that can help you with advice.
Cheers
are you 'simple but elegeant'?
Personally, I cannot understand why anybody would use CMU over a solid pour for basements.
CMUs are very porous, water goes right thru them.
There is a built in fracture at the end of every block.
You must fully fill them, might as well just pour.
You have to cut out one side of every void in the bottom course to remove all the grout slag, then plug the holes for the pour.
The cost of the block is more than the cost of the forms.
Most block layers insist on watering down the 'crete so it will flow easier.
They don't like to run vibrators down deep enough.
You can't reliably place the iron in the inner 1/3, where it belongs in a basement wall.
Nobody wants to pay for enough rebar to place one on each course and 16" OCH is too wide IMO. OTOH, 8"OCH is closer than needed.16" OCV is fine.
SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
A bond beam won't be sufficient in a tall wall because it runs horizontally. You'd need to pour cores from bottom to top, with rebar in them. I'm not an expert, but generally I've seen poured cores about every 4 feet or so.
In colder climates concrete block is a terrible material to construct a home with. It's very porous to exterior moisture. Its insulating value is nil, so the interior wall surface is quite cold in the winter and very prone to mold. Our church had a small building that was converted to temporary quarters for guests. When occupied on a longer term basis it developed a mold problem so serious we had to tear it down. The mold remediation and reconstruction would have cost more than starting over from scratch.
If I were you I'd construct your basement from ICF's (insulated concrete forms). These are hollow insulating foam blocks that stack like Legos and are reinforced with rebar and poured solid with concrete. The forms remain in place and act as insulation. The exterior has to be suitably waterproofed. You get a very high insulating value for a foundation and a strong foundation.
The material cost is higher than plain CMU's but studding and insulation is already in place. (The forms have locations to which you fasten drywall directly, eliminating the need for actual studs.)