what to use in gap between concrete floor and basement block walls

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02-18-2008, 06:26 PM

Location: Sometimes Maryland, sometimes NoVA. Depends on the day of the calendar week ane,501 posts, read xi,343,358 times Reputation: 1132

Our house is 40 year former. When nosotros moved in, the basement was finished, but probably 30 years ago. Moldy indoor/outdoor carpet, no insulation backside the wood paneling. Yucky! So, thats all gone at present. We are down to the cinderblock walls and original floor (mayhap VAT :\). Split foyer home, basement slab is about iii feet beneath course. We have seen no water intrusion since we moved in last May, and we have had some doosey of rain storms. So I'grand not too worried most flooding basements. We think the moisture before was just poor insulation resulting in high humidity levels. There is a gap nigh 1/2 inch broad all the way effectually the slab between the slab and the foundation wall. From what I accept been reading, we should caulk the gap. DH thinks that is going to take as well much caulk and nosotros should use expanding cream, I'm pushing for some sort of caulk, crusade thats what the books tell us to do. OTOH, someone said the gap is so that any water that gets into the wall tin run down into the footing, suggesting nosotros should not caulk the gap. This gap is not tied to the sump pump nor does it appear to be part of the waterproofing system (both the sump and waterproofing are in the garage but). So anyway... anyone with building feel, tell me nigh this gap. Whats information technology for? Why is it in that location? What is the electric current thinking on information technology - seal information technology with caulk? Would expanding foam be OK? And FYI, we plan on insulating to the current guidelines from free energy.gov (vapor barriers, batt insulation, etc).

02-18-2008, 08:31 PM

I'd brand certain it'due south non role of french drains that were put in to keep the basement dry out before I filled the gap.

02-19-2008, 12:18 AM

harborlady 11,944 posts, read thirteen,932,612 times Reputation: 2772

The gap you see is chosen an expansion gap or expansion joint. It's supposed to be there considering concrete shrinks/stretches with temperature. You're in maryland and then thats a libation region with humidity, and my estimate is you lot don't take insulation on the outside wall. Are you close to the coast? The h2o table might be high in your area. You might want to invest in consulting with someone who can get to the bottom of where the moisture is coming from earlier y'all exercise annihilation. If you have an thought of when it was put in, yous might be able to find out what local codes were in effect by calling the town. If they didn't put poly plastic down the slab might exist wicking moisture up from the ground. Here's a link that should give you an thought of the bigger picture show. Build Your Ain House - Concrete basement floors & garage floors - Home Improvement simplest answer if moisture weren't an result- The caulk vs foam= I've used both, the caulk lasts longer and makes a improve seal. I've gone dorsum a year later to where foam was put downwardly (outdoor industrial awarding) and bugs ate holes in it. Wasps are oddly attracted to information technology, no clue why or what else would be noshing on it. Use a wheeled crawler board to sit down on while applying the caulk, it will salvage your back and knees a bit.

02-19-2008, 01:16 PM

Location: Johns Creek, GA 15,802 posts, read 58,860,895 times Reputation: 19919

The gap is just shrinkage. Information technology'due south not there by design. When the foundation is built, it is congenital in this sequence- ground, foundation walls, so the concrete slab. The walls act as the class for the slab. As the slab cures it shrinks. Caulking is probably not a bad thought- information technology may limit the infestation of insects from beneath the slab. Equally far as the walls are concerned, and the age of the dwelling- the block wall foundation is probably just damped-proofed, not water-proofed. And since block is quite porous I'thousand certain you have a high moisture content in the basement area. Use a vapor bulwark (6mil) against the wall, then employ unfaced batts of f/drinking glass insulation in the stud wall.

02-nineteen-2008, 04:27 PM

harborlady 11,944 posts, read 13,932,612 times Reputation: 2772

Quote: Originally Posted past Yard'ledgeBldr The gap is only shrinkage. It'due south not at that place by design. Architects deliberately proceed this gap in their plans. Whether by auto cad or traditional pencil dwg translated to blueprint, it's by blueprint.

02-twenty-2008, 05:xviii PM

NorthmeetsSouth Location: Marietta, GA 857 posts, read iv,713,050 times Reputation: 838

I take to go along with KledgeBldr on this one. I ain a construction company and I have never done an expansion joint effectually the perimeter of the basement slab. As he said, the walls serve as the form for the basement slab, and then it is poured right up to it and what you are seeing is, no doubt, some shrinkage.

02-twenty-2008, 06:nineteen PM

harborlady 11,944 posts, read 13,932,612 times Reputation: 2772

Quote: Originally Posted by NorthmeetsSouth I take to go on with KledgeBldr on this 1. I own a construction company and I accept never done an expansion articulation around the perimeter of the basement slab. As he said, the walls serve as the form for the basement slab, and then information technology is poured right upwardly to it and what you are seeing is, no doubt, some shrinkage. What if you ignored the blueprint and somehow tied the slab straight into the wall with a single pour like giant a square basin? My only point is it's no fault there's a gap. Architects and drafters are schooled to account for this gap, how it happens in the field is the realm of builders delivering that result.

02-twenty-2008, 08:14 PM

Location: Sometimes Maryland, sometimes NoVA. Depends on the day of the week 1,501 posts, read 11,343,358 times Reputation: 1132

thanks for all the opinions. The responses are interesting. I expected it to be an easy question. hmmm In example anyone is interested, I've attached a couple pictures of the gap. These were all taken in one corner, but information technology looks the aforementioned the whole way around. Does it modify any thoughts? Still thinking caulk? edited to add together: looking at it, 1/two" might be a bit underestimating. And the business firm is 40 years old this year.

02-21-2008, 11:53 AM

NorthmeetsSouth Location: Marietta, GA 857 posts, read 4,713,050 times Reputation: 838

Quote: Originally Posted by harborlady What if you ignored the pattern and somehow tied the slab direct into the wall with a single pour like giant a square basin? My only point is it'south no mistake there'south a gap. Architects and drafters are schooled to business relationship for this gap, how it happens in the field is the realm of builders delivering that consequence. Basically, pouring it like a giant square basin IS how its washed... and I accept never seen a set of plans that phone call for a gap around the perimeter... just to exist sure I just checked the xiv different plans that are sitting on my desk, but maybe your architect has a different method of doing things.

02-21-2008, 01:58 PM

harborlady 11,944 posts, read 13,932,612 times Reputation: 2772

Not my architect, my drafting schoolhouse. I'1000 a drafter. I don't ever go to know why, I only gotta practice. Why? Because they say and then. LOL

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