I have a house that has been rebuilt on existing Cinder Block Wall and a dirt crawl space. I have covered floor and walls with Plastic to keep moisture out BUT, I believe moisture is coming in through the top of the cinder blocks as they are unsealed. Any suggestions on sealing them would be helpful. I am thinking of using an additional 2×4 to extend the plate over the block and glueing.
Steve
Replies
Greetings sj,
This post, in response to your question, will bump the thread through the 'recent discussion' listing again.
Perhaps it will catch someones attention that can help you with advice.
Cheers
Are the cider blocks open or filled - can you see or feel down the holes in their middle?
What's the outside of the cinder block walls look like? Dirt up against them? How's drainage and runoff from the roof/gutters? Any waterproofing on the outside walls - tar, plastic, foam boards?
How high is the cinder block wall that you're talking about?
Griff
Are you talking about the interface between your cinderblock foundation wall and the rim joist of your house?If so, why not get someone in to spray the area with polyurethane. I did mine 3" deep. Completely covered the rim joist and sealed up over the foundation wall. Really cuts down on drafts.That cost me $450 Canadian last fall.If my house wasn't a 100 years old... there would go a really fine hobby.
"...spray the area with polyurethane.."
Do you mean Poly-Isocyanurate foam? Good stuff, seals up leaks. Don't know how good it is about stopping migrating moisture being wicked up or through cement blocks.
Maybe it works there too, I'm just not familiar enough with it to say definitely.
I was just trying to get the HO to spell out some of the other conditions in the home. Stopping or reducing the flow of water to the cement blocks is probably as important as stopping it from entering the house. Less moisture getting to the cement blocks means less being wicked into the interior of the crawl space which means less moisture to block at that point.
Good-stuff and other polyurethane foams (closed cell or not) do not repell moisture. Only XPS limits its uptake to 3% or less, which is why you can frequently see it under floats at the marina. I would not use anything but XPS in areas that can get wet.Ideally, you'd have the opportunity to dig out the foundation on the outside, install a geotextile burrito with a 3/4" aggreagate and a perforated drain filling (with a cleanout!) that drains to daylight. The roof gutters would also drain into a separate drain. The exterior wall would then be covered with Rub-R-Wall and Dowfoam XPS to keep the water out. and to make the wall a part of the thermal mass of the house.In the real world, few people have the means (or the energy) to do so, and hence try to rely on indoor approaches, such as internal drains, sumps, etc. Another thing you could try is to line the pond to limit its ability to make the groundwater swell around the house.
Good points all. Thanks for adding them.
Draining a pond, huh? That's got to be a heck of a job, esp. if it's fed by underground springs.
Could you excavate a trench say half-way between the house and the pod (assuming the pond isn't 20 feet from the house) and lay in some kind of impermeable barrier to slow/stem water migration? I would think you could have a back hoe get down 8' to 10' without too much of a problem, if there was no ledge or large boulders in the way. Drop in a plastic liner and back fill? Sort of like a large curtain in the earth encircling 1/2 of the pond.
>>If so, why not get someone in to spray the area with polyurethane. I did mine 3" deep. Completely covered the rim joist and sealed up over the foundation wall. Really cuts down on drafts.>>That cost me $450 Canadian last fall.You have to be careful with that approach in areas with subterranean termites - they can tunnel up behind the foam and get into the wood framing undetected.
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Sojourners: Christians for Justice and Peace
Thanks for replying. The cinder block walls are empty. I don't have gutters on one side but I installed a drain pipe under rocks and this year I put plastic on the drip line with rocks to hold it in place.
The other side of the house is close to a pond and when the water in the pond rises I get ground water and my sump pump goes like crazy. That is only in the spring but the heat is still on and that keeps the basement dry (furnace in the basement).
The foundation is probably old style cinder blocks as they are not as strong as cement. But dirt is on the outside walls with no sealant or insulation. I have put plastic on the inside (as an article in Home Building suggested) but moisture continues to build in summer (84% humidity).
I think it is the walls but am not sure how to moisture seal the holes. The article suggested stuffing plastic bags - but, I can't get enough space to make sure they fit well.
Sj
I'm not sure how best to rectify your problem.
I think I'd start a new note entitled "Masonry Question" to get the cement guys to put their thinking caps on - they may not necesarily respond to a general HO question. I'm sure you'll get several responses on the best way to plug up the gaps in the cinder blocks, and then try the sprayed in poly- iso to finish the job. Is expensive - not a HO capable job - but worthwhile.
Good luck.
Griff
There was a fine homebuilding article a couple of years ago (or so) that covered this exact situation. The situation was to stuff something into the concrete block cores on the top to keep the moisture from migrating up. I think that the contractor used wadded-up plastic bags.
Thanks for all the input. That Fine Homebuilding article was excellent and I attempted to do all of the things recommended except stuffing plastic bags into the block. In fact I even had the company out to the house once and he suggested simply putting plastic on the floor.
Unfortunately, the rim plate covers too much of the blocks hole to stick the plastic bags in. I was thinking of extending the rim joist with a pressure treated 2x4 and using construction adhesive to seal the block. Just am not sure that it would work. I am not sure that drilling holes will keep the moisture out as it seems it would still come in through the top of the block.
Unfortunately, I can't put exterior french drains around the outside as I am too close to my septic tank (15 feet). I am not only next to a pond and a lake but I am also at the bottom of a hill.
Steve
As for a conditioned crawl space are you talking of dehumidifying it?
To seal up the holes in the concrete block, why can't you just insert the plastic tube from a can of expanding foam - how large does the hole have to be to do that?
If need be, build up the foam as filler in layers - insert some, allow it to cure and harden for an hour or two, and go back and add some more until there's enough foam that the hole is closed off somewhere in the middle of the block (a small amount of foam should stick to the sides more than simply fall to the bottom due to its weight).
Then fill the remaining cavity with the foam till you get to the top of the top row of blocks.
A couple, or more, of the cans should do the trick at far less cost than calling in an isocyanurine (? sp) contractor. Shave off the excess if necessary to install your PT slab, although I wouldn't think it would be necessary at that point.
As far as your problem outside the house, why couldn't you dig your trench and lay in a double set of pipes? One slotted collection pipe in gravel with "T"s every 4-5 feet sloped down slightly to a parallel running solid 4" PVC drain pipe 3' away to gather the runoff and divert it somewhere away from the septic tank/leaching field. Just don't forget to install "T"s coming up from the solid pipe to the surface with a twist off cap to allow the pipe to be snaked to bust up any obstructions that develop over time.
Yes, it's at least double or triple the work and supplies of a normal drain system but, then again, you don't have the normal water situation.
That and a good set of gutters and leaders should help you minimize migration under and into the crawl space.
And, sure, why not put a dehumidifier (and fans) down there? Wire them to a quality humidistat (such as used with better quality bathroom fans) and don't rely on the one in the dehumidifier. Connect the dehumidifier drain to the solid runoff pipe. Or install A/C vents if your system can handle it?
And, just to be safe if you do install a dehumidifier down there, install smoke detectors (just in case) in the crawl space hard wired to other smoke detectors in the house so you can hear them when they go off.
Griff
Conditioned crawl space: plastic on the floor, insul on the walls, and conditioned air from the forced air HVAC system - i..e, add some registers in the crawl.
But it sounds to me like you need some expert help on site, given the conditions you have.
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Sojourners: Christians for Justice and Peace
Edited 7/7/2005 4:53 pm ET by Bob Walker
The CMU should have a vapor barrier between the top of the CMU wall and the wood structure. I don't have a clear enough picture of the construction of this foundation to offer more than that at this time.
Your problem is with the thread title -- "Moisture proof basement". That's an oxymoron.
1st thing: move water away from the house: gutters and 10' downspout extensions and positive grading for 10'
2nd: where are you located?
3rd: where is the moisture problem, the basement or the crawl space. Mainly at corners, or concentrated in some area or everywhere?
4th: with an older house (especially with limited exposed block above grade outside) I strongly recommend against running plastic up the foundation walls to the sills in the crawl.
That keeps moisture rising in the block; older houses usually didn't seal (or seal well) between the foundation and sill plate; and you can end up with badly rotted sill plates.
This happens! (At least in NW Ohio) I have seen it often!
Consider an conditioned crawl (if you use central A/C in the summer.)
If the foundation is much older than 50 years or so, whatever damp-proofing was applied is probably a mere memory (at least in my area.)
see also, the Building Science web site
The best way to keep the water and moisture out is to actually let it in. If you do the work on the inside and dill every core of block at the bottom and allow the water to freely flow into pipe that heads into the sump then the block will actually dry out because the water runs through it rather than filling up into it. I just had this work done at my house and now my children are finally healthy after 2 1/2 years.
The best way to keep the water and moisture out is to actually let it in.
An alternative approach, that I've used very successfully, is to create an umbrella around the house to keep the dirt against the foundation dry. As we live in what amounts to a walk-out basement, with no house above, letting water into our interior would be a catastrophe.
Pretty sure our house air is at least the equal of yours. Dry is good.PAHS Designer/Builder- Bury it!
>>An alternative approach, that I've used very successfully, is to create an umbrella around the house to keep the dirt against the foundation dry. Interesting. Could you give some details?
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Sojourners: Christians for Justice and Peace
Sure. To keep it within reason, here's a link: http://www.axwoodfarm.com/PAHS/UmbrellaHouse.html , which doesn't seem to be working tonight.
Anyhow, for a traditional house, layers of 6 mil poly attached to the house and sloped away from the house, to a french drain. For PAHS (Passive Annual Heat Storage) we use XPS within the poly umbrella.
This presumes a higher-than-water table house with the aim of directing ground water away from the house. We deal with an area (ideally) 20' greater than the perimeter. How much this can be infringed upon will depend on the soil. Due to trees here, I'm as close as 12'. The 20' has to do with our PAHS cooling/heating passive system. Dry dirt next to the foundation is a beneficial byproduct. Water/damp-proofing has proven to be unnecessary.
As long as there's no landscaping penalty, it's incredibly cheap and effective.PAHS Designer/Builder- Bury it!
Thanks. Very interesting
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Sojourners: Christians for Justice and Peace
>>The best way to keep the water and moisture out is to actually let it in. If you do the work on the inside and dill every core of block at the bottom and allow the water to freely flow into pipe that heads into the sump then the block will actually dry out because the water runs through it rather than filling up into it. I just had this work done at my house and now my children are finally healthy after 2 1/2 years.Perhaps as an expensive, last desparate effort or in very high water table situations....Keeping the water away from the house is usually the least expensive and best approach, in my experience.E.g., if most of the moisture is coming in at the corners (where there are downspouts), downspout extensions will usually do the job.But, of course, there is no "one size fits all" solution.
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Sojourners: Christians for Justice and Peace
Here's a link to one inexpensive option for the downspout extension solution that I use. This one self-extends and self-retracts - otherwise your fixed downspout extension would be in the way of a sidewalk, driveway, garden, lawnmower etc.
http://www.rainguardusa.com
-Brian.
I'm not anbig fan of thopse roll out doobies.I don't see many. Usually, when I do, they've aged and are not rolling back up.The main thing, though, is that they don't get the water past the overdig area, so all you're doing is putting a concentrated amount of water at the foundation below the downspouts.Assume 4 downs on a 30x40' house.In a 1" rain, that's 210 gallons at each down location - that's about 7 trash cans worht at each spot.
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Sojourners: Christians for Justice and Peace
While there are some shorter (cheaper) ones, 6 feet long "Rainguard" extensions like the ones I have get past the overdig, (unless it's one BIG overdig), and that's more than my municipality recommends. I don't think they're meant to compensate for a settling overdig that eventually slopes toward the foundation, though. I've had them for over 3 years now and once a year or so I remove twigs and dirt and then it retracts like new. Solved my wet basement problem, that 210 gallons now being discharged 6 feet away from my foundation, and no pipe to trip over and kill the grass.
- Brian