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Old 09-05-2008, 09:32 AM
 
Location: Sometimes Maryland, sometimes NoVA. Depends on the day of the week
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We are thinking of working on our basement this weekend, since Hanna will ruin our outdoor plans. We need to attach a vapor barrier to cinder block foundation wall up to grade. Construction adhesive sticks to the block but not the vapor barrier (10mil poly I think). Googling is not helping me. How on earth do I get the vapor barrier to stay against the wall?
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Old 09-05-2008, 09:49 AM
 
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Default waterproofing..........

Get some waterproofing stuff. Looks like tar, comes in 1 or 5 gallon buckets. Thinner than tar. Open, stir well, apply with a roller. Let it get tacky, stick the poly to it. Should work well. The waterproofing will dry hard if you let it set long enough.

Can use it in a number of spots, I've even used it to glue down vinyl flooring. Just have to know to let it get tacky enough. In most cases, you can remove the poly, flooring or whatever in the future by just peeling it off, another advantage to the stuff.
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Old 09-05-2008, 10:00 AM
 
Location: Sometimes Maryland, sometimes NoVA. Depends on the day of the week
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Wow! Thanks for the quick response In time for me to even make it to the depot on my afternoon errand running. I hadn't thought of that, although I did contemplate using drylock paint and sticking the barrier to it while it was wet. LOL Do I need to apply to the whole wall or just a band at the top to keep it held up to grade? (That will be the difference between 1 and 5 gallons).

Its kind of frustrating, this is a step that I know we need to do, but there is so little information on it. The books just say to attach a vapor barrier, the vapor barriers don't say how to attach them, and HGTV never shows anyone doing it LOL

Last edited by rubytue; 09-05-2008 at 10:09 AM..
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Old 09-05-2008, 10:20 AM
 
Location: Somewhere in northern Alabama
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If you are putting in a vapor barrier on the inside of a basement, then you want to run it the entire height of the block or poured wall. Concrete block especially wicks moisture, and that damp spot below grade will simply migrate to above the vapor barrier. If you put a vapor barrier or water barrier on the outside of a concrete foundation wall, you want to stop the barrier just above the splash-back point from water that hits the ground.
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Old 09-05-2008, 10:32 AM
 
Location: Sometimes Maryland, sometimes NoVA. Depends on the day of the week
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really? That goes against everything I have read and what our structural engineer said. Vapor barrier against the block to grade, then framing and insulation with a second full height vapor barrier (like the one on the insulation) behind the drywall. Theory being that water behind the outside barrier goes to the french drain, water behind the second one goes through the block wall (water vapor would come both in and out through the block, but won't hit the drywall or the finished space).
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Old 09-05-2008, 11:34 AM
 
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Default Well if it is a block wall

It is normal to waterproof the wall itself on the outside, applied directly to the block. Done before backfilling. They use the same waterproofing stuff out of the bucket. Ocassionally you will see some folks do a second coat after the first has set well, takes a couple of days. Dries to touch in about a day.

Then they may apply the second coat, followed by poly sheet and then rigid insulation board. Usually they just use the waterproofing stuff to stick stuff together. Then it all gets backfilled. Normally only comes up to grade level with this treatment on the outside.

I guess you could use it inside over the entire surface, don't normally see it done that way, hopefully the contractor already did it outside. Can be sort of good insurance if you are planning on studding and finishing off the basement.

You can use this same idea for waterproofing areas inside like behind showers, surrounds, etc in the bath. I always do a full sheetrock, then treat the area in question with either an oil based paint or the waterproofing stuff, let it get tacky, good olde poly sheet over the top, quick, cheap, easy and pretty effective. If you are tiling then it is Durock over top that and then tile.

Lots of ways to skin the same cat, they all use about the same methods.

I take it the house is already built, backfilled and you are going this treatment on the inside basement wall before finishing the basement. In that case I would probably go whole hog and treat all the surfaces with waterproofing, not very expensive stuff, pretty easy to apply. Poly sheet over top the waterproofing is really a belt and suspenders approach, especially if the outside is already waterproofed, sucker should be able to float like a boat. just make sure you don't drip any on the floor, not that easy to clean up neatly. You clean it up with paint thinner.
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Old 09-05-2008, 11:59 AM
 
Location: Sometimes Maryland, sometimes NoVA. Depends on the day of the week
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Oh yeah, the house is already built. 40 years ago LOL

The basement was "finished" when we moved it. As in, furring strips tacked to block walls, circa 1972 paneling on top of that, and indoor/outdoor carpeting over top of vinyl tile on the floor. (The closet in the bedroom was built on top of the "carpet.") When we moved in, about 18 months ago, it was mildewy, but not really damp. More just 40-year-old dank. We ripped everything out almost immediately, to investigate the mildew. Discovered there were no obvious places of water damage, no rotten areas, no true moldy spots. So we just chalked it up to 40 years of non-insulated basement dankness. In the year+ since everything has been down, we have tested the block for condensation (sealed some squares of poly in different spot) and found nothing. We have also had no water problems. Last summer was fairly dry, but this has been a wet year and we did have a tropical storm roll through last year. We are about to have our second tropical storm. I am pretty sure if we weather that, we should be fine for 99% of the weather around here. A true hurricane might be an issue, but where we are in MD, those are fairly rare (Isabel was the last one in 2003). Oh, we also had the couple of cracks in the blocks evaluated by a structural engineer. He said they were not structural and told us how to seal them. It cost me $250, but I figure after 40 years, since we had it opened up, it was a good time to have it evaluated (especially since a friend of mine has a similar aged house, and her foundation needs to be completely redone. There are placed where some blocks are an inch or two off plumb from other blocks!)

So thats the whole story I do want to do it right, but honestly, I'm not terribly concerned about rivers flowing into my house. Just the normal moisture in the air. My location makes it kind of difficult b/c we have to deal with hot, humid summer month and reasonably cold winters. So you have to account for both.
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Old 09-05-2008, 01:30 PM
 
Location: Knoxville
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If you are going to use Drylock paint, then take the time to read the instructions on the can. It usually says to use two coats, AND to overlap it onto the floor for a couple inches. You usually have to do the 2nd coat within 24 hours of the first coat, or you have to put in an additive so it will stick to the first coat.

Get the crack filling stuff that Drylok makes and fill in the cracks. You can also get a caulking for concrete that works well too for the larger stuff.

I can tell you that the 2nd coat is very important. YOu will be surprised of the little nooks that get missed on the first coat.

Don't bother trying to put the moisture barrier to the wet paint. It will likely peel off when the paint dries.

My feeling is that if you have not had moisture coming in, and you have addressed soil slope and downspouts on the exterior, then the 2 coats of Drylok will probably be fine.

Have fun!!!!
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Old 09-05-2008, 03:58 PM
 
Location: Somewhere in northern Alabama
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Quote:
Originally Posted by rubytue View Post
really? That goes against everything I have read and what our structural engineer said. Vapor barrier against the block to grade, then framing and insulation with a second full height vapor barrier (like the one on the insulation) behind the drywall. Theory being that water behind the outside barrier goes to the french drain, water behind the second one goes through the block wall (water vapor would come both in and out through the block, but won't hit the drywall or the finished space).
I'm not understanding any appreciable difference? Visualize a free standing concrete block wall, built up from the slab of a poured concrete basement, prior to any backfilling. For the example, we'll say the basement will be to the left of the wall, the backfill to the right. The primary place you want to prevent moisture intrusion is from ground water and runoff from the roof on the right side of the wall. You mastic the exterior (right side) of the concrete to the grade level. You then backfill, starting with crushed stone, then perhaps a drain pipe with a silt barrier, dirt, and finally topsoil.

The above works fine if the house is guttered properly and the slope goes enough away from the house to carry the surface water off. What happens in some real-life situations is that a lack of a gutter or a driving rain can have water splashing on the dirt and stones next to the house, and spattering up to 18" up. By extending the waterproofing slightly ABOVE grade, say 6" to 10", then bulk of that splash-back will not be able to penetrate the concrete. The mastic also forms an additional barrier to ants and other insects. The second course of block above grade can be treated with a water permeable treatment, such as latex paint without the primer, brickwork, or stucco (sparging). That area allows any moisture in the block an easy way to exit. This sill or mud sill sits on top of the block, and should be of either pressure treated lumber or something resistant to moisture, or sit on a neoprene barrier.

On the interior of the basement, on the left side of that wall, you have an unusual situation. Not only can the concrete have moisture in it, it will be cold enough on humid summer days to have moisture condense on it. (Winter air is usually heated and drier, so it isn't as much an issue in the cold months, even if the wall is colder in winter than summer.) Anyway, that moisture that condenses will migrate inside the block and keep a general dampness in the basement, making it feel like the typical, "eww, this is too dank down here to use this space" type of cold humidity. Additionally, in some situations, ground water can be significant enough at the foundation/wall joint that moisture can wick up from it and invade the basement space.

There is no perfect solution to all all that condensation and moisture. What I discovered, after long thought and some experimentation, is that a barrier of plastic against the interior of the block, going all the way to the top of it, will seal out any intruding moisture, away from the basement and into the block, where it will either migrate upwards and evaporate off the unsealed surface of the top blocks, or downward to a rim drain around the interior perimeter of the slab.

That plastic barrier doesn't resolve the condensation problem though. It requires one of two solutions. The first, which I used in a laundry room with a severe moisture problem, is to use 1" furring strips and cover the plastic sealed wall with masonite pegboard that has been given a quality watertight sealant on the back. A dehumidifier exhaust is then ducted into the bottom of the space between the pegboard and the wall. Since the air coming out of the dehumidifier is both dry and slightly warmer that the room air, the pressurized dry air will absorb the moisture that might have collected on the plastic, and the vapor and air will escape into the room from the holes in the pegboard. As the dehumidifier cycles, it eventually clears the air of moisture, and the warming action of the dehumidifier exhaust raises the temperature in the space between the pegboard and wall, to a point where the wall warms and no longer condenses the humidity out of the air. I really should have patented that idea, but whatever. I've never seen anything similar, and it works like a charm.

In a less humid basement space, the wall can be insulated with standard insulation and a second vapor barrier applied on the interior (living space) side. The trick here is again something I've never seen anyone else do. The TOP four inches of the vapor barrier are removed., even though the insulation goes completely to the top. In a basement space, there is typically a few degrees of temperature difference between the floor and ceiling. The floor therefore has a high relative humidity, and the ceiling a low one. As an insulated wall cavity heats, any moisture in it starts migrating to the top, where it can escape from the break in the vapor barrier. When the room cools, the last place to cool is the area near the ceiling, and therefore the relative humidity up there remains low, so little moisture has a chance to wick down into the insulation.

Using these techniques and a few others, I was able to transform a house where the basement was like a boat riding in the water table. I was actually able to use regular sheet rock below grade and not have it mold, even as the sump pump was constantly removing water from that same basement.

As for what others recommend, I don't much care. I know what works when the alternatives are costly and often impractical digging and raising a basement above ground level, or abandoning use of the space altogether.
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Old 09-05-2008, 04:36 PM
 
Location: Sometimes Maryland, sometimes NoVA. Depends on the day of the week
1,501 posts, read 7,734,754 times
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Quote:
Originally Posted by harry chickpea View Post
I'm not understanding any appreciable difference?
Well, the different in my case is about 4 feet Basement is only half under grade. Full size windows and such. So, when you said to go up to grade, it was a large different. Like double. Plus, from everything I have researched, you never want two full vapor barriers because moisture can get trapped between them. You solution is to leave the 4" gap at the top on the inside. Mine was to only have the poly barrier to grade.

But, I think I may have solved my real problem. I couldn't find cosmic's "tar-like" waterproofing stuff. But I did find a polyethylene based construction adhesive that says it bonds to concrete, brick, and plastic.
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