I am thinking of using almost a second vapor barrier on basement walls 4

[VaporBryan]

I just bought a bungalow built 1960 up north. The basement walls are cinder blocks. They are damp. I am thinking of breaking the slab on the inner perimeter and installing a french drain pumped out by a sump pump.
I am thinking of placing a vapor barrier on the cinder blocks (because they are so damp) From the top to the bottom of the french drain. I am then thinking of finishing the basement. Using wooden 2x4" and pink fiberglass matts covered with drywall. Since the vapor barrier should be behind the drywall, I am thinking of placing a second barrier there. Both barriers will drain into the french drains with spacers. The french drain would be covered with cement except the two spacers which will allow each barrier to individually drain. Both barriers will be sealed at the top and open bottom to remove trapped moisture. I think??

 

[oldestguy]

Moisture travels from warm side to cold side in the usual outside above grade building wall. Why would you want to trap block water between two barriers where the wood can rot? If you are heating the basement, then perhaps the inside barrier is OK, but then none on the blocks. Not sure what you mean by "sealing" vapor barriers.

Before going too far with vapor barriers, determine why the walls are damp. You may be just having moisture from the floor area condensing on the cool walls, especially in summers. That's a common situation in some basements I have seen. What's the outside look like as to surface water drainage? Ground water flow?

Fiberglass insulation can take on water like a sponge. Mice like the stuff also. Pink closed cell extruded polystyrene won't take on water.

As to your "French Drain", do some reviewing of my advice found on those forums dealing with that term.

 

[Ron]

Don't sandwich anything that absorbs moisture between two vapor barriers. Moldfest and material deterioration.

 

[SteamBryan]

The double vapor barrier will have a bottom drain
Please see attached.
I do not want to trap the moisture.
Bryan
PS:I changed my handle

 

[SteamBryan]

Oldestguy,
The house has no surface drainage. I am correcting this with downspouts that remove most of the roof's water over 12 feet away. I will raise the slope on the outside perimeter.
The walls are damp even halve way up so I thing drainage is a big factor. But, I suspect that the slab might not have a vapor barrier below it??
I am installing the internal French Drain thinking it will catch all the water trying to get underneath the slab??
I am trying to hope that having the two barriers open to a bottom drain that the moisture will not build up??
Regards,
Bryan

 

[SteamBryan]

If the moisture does not drain, I am thinking of putting a humidifier attached to the French Drain??

 

[SteamBryan]

I meant Dehumidifier

 

[oldestguy]

Brian:

You have replies from two old engineers who have seen a lot of problems out there, such as mold, law suits, wet basements, caved in basements, and varied personal experiences. From your replies, I'd guess you have not looked up French Drain forum discussions, nor have you considered some of the warnings. I assume you know how much water a sponge holds before it starts to release some.

In doing the outside slope work, there is a technique that many engineers, architects and landscapers do not know about; water proofing the ground surface. If interested I can give the details.

As to French Drains, my Master's Degree Thesis dealt with drainage of wet ground by subdrains. Conventional "French Drain" details can fail.

 

[oldestguy]

Brian:


This link has some comments that may help explain my thoughts.

http://www.eng-tips.com/viewthread.cfm?qid=290956

 

[SteamBryan]

Oldestguy,
I did read the French Drain stuff, but only found one thread on inside French drain. The problem was not the drain but an oil pipe installation?
The drain had no problem functioning.
I would like to hear your information on waterproofing the surface.

The walls have bowed in 2 inches. I was thinking of straightening them first. Then bracing 2x4's to retain the wall straight. I would like to use a vapour barrier to protect the wood.

Pink closed cell extruded polystyrene won't take on water, true but, if I have the wood every 16" and the extruded polystyrene between them, the wood would have mold & smell? That is why I am thinking of putting the barrier.

If I do not use a barrier, I would have to use the metal 2x4. But they conduct heat and I do not think as strong?
Bryan

 

[oldestguy]

Before making any final plan, find he source of water. Is it moisture from inside? from outside soil? Each has its own treatment. If it is truly from the outside, only the sheet against the block is needed. I suspect that.

Exterior ground surface can be made waterproof in this way. Assuming the surface is in its final position, then do this. Leaving walks and bushes, all the surface where fill was placed, strip the sod. Place a powdered bentonite (not the granuated kind) on that surface at a rate of about 3 pounds per sqauae foot. Powdered bentonite is available at plumbling supply houses in 50 pound bags from under various names for "driller's mud". One name is Volclay. It is a volcanic clay that has the particles made up of parallel platelets which electrically attract water. Given free acess to water it can swell 16 times is orginal volume. However, in soil it will fill voids and keep the soil moist and rather impervious. You mix that in with a rototiller about 3 inches deep. Thorough mixing is needed. If you feel ambitious, you use a concrete mixer or mix by hand in a wheel barrow. Then re-place the sod. If you use too much bentonite, it will turn the lawn to mush. It is a natural clay so grass now grows better. The required treatment distance out from the house is the whole zone of backfiliing to the basement. In may cases this is as much as 10 feet. If you do not know that fill width, at least as far out as the height of the wall. At cracks in walks next to a foundation, fill a mix of sand and bentonite.

With the wall buckled in some, that brings up a whole different picture. Sounds like frost has shoved the wall in. Very common with block walls. Insulate the wall and less heat goes out, making mister frost even more vicious.

Pushing the walls straight may be more than you want to try. There is earth out there. Some suppliers furnish a bracing system that at least keeps it in the present position. No way will ordinary wood or steel studs do that if more frost push is coming.

Here is one system:

http://www.aquaproof.com/structural-repair/gorilla-wall-braces

Another:

http://www.permajackofstlouis.com/basement-wall-bracing.htm

I once saw a system that looked like a bow for bow and arrow. One even installs structural steel members.

If you really want to stop frost push, you need to do one of three things; remove cold, remove water, or change soil to non frost susceptible. Water can get there by capillary action, so draining the footings won't do it. Even the surface drainage fix won't fully do it, but helps. Insulating the outside can help, such as leaving snow there or a layer of fall leaves each season. On new jobs we even recommend burying a sheet of the pink stuff about a foot down, to 4 feet out.

Non-frost susceptible soil is sand with less than 5% passing the number 200 sieve (a size hardly visible to the eye).

Turns out to be quite a project, huh?

Reminds me of a village where they decided to avoid winter frost heaving of the new streets. They laid down a sheet of pink stuff, then the base and paving. In winter, the warmth in the ground was retained there and the pavement got colder than the roads in the country. A freezing rain came down in early winter. In the country the warmer road was just wet. In town it was glare ice. Those folks coming in from out of town sure got a surprise. Fixed one potential problem and caused another .

So you may fix one thing and cause a few problems you didn't expect. I hope our info helps. At least now it is more complicated.

 

[oldestguy]

One more item:

I had assumed you were aware of the limitations of plastic vapor barriers. They are not that great. In addition to perforations such as nails and openings that are hard to seal, they do transmit moisture, even though slow. So your "seal is a good thought, but it won't fully stop moisture transfer. Your drainage openings at the bottom are obvious sources of vapor to go to cooler places, such as cold outside walls.

 

[SteamBryan]

OLDESTGUY,
The more complicated, the more interesting.
Thanks for the great insight!
Regards,
bryan

 

[Ron]

Oldestguy has given you some terrific insight. Listen to it. It doesn't make any difference that you have a drain for the sandwiched vapor....materials absorb moisture without regard to drainage. You can have all kinds of drainage for your cavity, but if the materials within the cavity will absorb moisture...you're screwed!

 

[a2mfk]

Oldestguy- great post, I saved your clay barrier idea to my library. I have seen this on foundation repair web pages, but not explained so well by an engineer. I deal with shrink/swell clay problems and this may be a low cost option to attempt to drain water and keep moisture away from the foundation to limit shrink/swell potential.

Not sure if it was already mentioned, but because you have a bow in your basement walls, you may also have expansive clay. I would do a hand auger next to your walls and see what you have. A local geotech firm can do this test fairly cheap. At least then you know the soils you are dealing with and that same firm may be able to help you a bit more with your drainage/moisture solutions.

Also agree with Oldestguy and Ron. I think this is correct:
Ideally your moisture barrier would be on the exterior face of the wall, but I would stick with one good one on the interior. In areas with basements, there are usually specialty contractors that deal with this exact thing. It seems you are a DIYer, which I am too and so full respect, but this one you may want some additional expertise on. There may be membranes that if installed by a certified installer offer some type of warranty.

Ron- do you think once this is all done you would just leave an air cavity between the basement wall (now covered by a moisture barrier) and then frame out your interior wall, insulate and drywall with NO additional moisture barrier? So you would not use paper-backed fiberglass either. That way the wall can breath and the heat/AC system or dehumidifier would remove any excess moisture from the air. You could also treat this the way some crawlspaces and attics are now- frame your interior wall with several inches of void space and run your heat/AC system through it with a return and supply, constantly exchanging the air and pulling out excess moisture.


Keep us posted, this is a good case study.

 

[Ron]

a2mfk...yes, that is correct....provided the waterproofing on the wall is never breached.

 

[SteamBryan]

Oldestguy, Ron, a2mfk,
Thank you all for your great insight!
I have decided not to double vapor barrier after Oldestguy's wise advise.
a2mfk,
The wall needs to be braced. Or, history might repeat itself? But, I could brace with carbon stripes every 4 ft.
My water surface drainage is bad. I am taking Oldguy's advise about the foam below grade. As well, I am greatly improving the surface drainage.
If I have expanding glay, can I not just brace the inside and forget about it?

Then, about your spacing design, do you think using pink fiberglass would be problematic in your design?

This vapor barrier drains to an interior French drain which is located beside the footing. (see sketch way above.)
I have broken the slab around the perimeter.I am presently testing for Radon. If radon is high, I would fear the spacer has to go?
If so, I am back at square one?
Best Regards,
Bryan

 

[oldestguy]

Hi Guys:

Now comes a question. Why any barrier at all? So moisture collects on the block wall. Maybe moldy I suppose. It also would collect on the barrier there. In this north country the main reason I see for a barrier is to keep water from collecting on the siding and in insulation there during winter. When I was a kid the outside walls had to be painted frequently due to that winter moisture collection ruining the paint adherence, but that was the main reason then for barriers. We had no insulation.

On the bentonite soil waterproofing treatment thing, the details came about due to a lot of lab work for landfill work. Also, it came from noting the layers of soil in most basement backfills sloping towards the wall and job problems resulting from that sloping condition directing infiltrating water. So, you treat the whole backfill area, even if slopes are good. No work on windy days. It really blows around.

My experience with expansive clays usually is reverse, with settlement from shrinkage. One job was compacted clay expansion aggravated by use of bentonite in the wrong place fed with roof water. I'd be interested in what experience home owners have when a basement waterproofer uses bentonite on the outside. None of these have come to my attention.

 

[a2mfk]

OG- you have a point. Once you improve the surface drainage, are we talking about a damp wall or actual water accumulation/penetration that would necessitate an interior trench drain?

Basements are a bit outside my area of expertise, but I found this:

http://www.epa.gov/indoorairplus/technical/moisture/1_12.html

I would consider using PT base plates too.

The bowed walls MAY go back more towards plumb if you have expansive clay soils that dry out. But a 1960s basement constructed with CMU probably is mostly unreinforced, and is probably not very elastic, so it going back into a vertical position may be wishful thinking. I am surprised you don't have a cracking problem. This is a separate structural issue and I would hire yourself a local PE with experience with basement walls in your area. Severely deflected unreinforced CMU scares me....

Your sketch also assumes the slab is down at the foundation level. I don't know what was/is common practice for basement construction in your area, but I would not be surprised if the wall was built first, and then the slab was built over the foundation, perhaps several inches above the top of the foundation. I also don't like the interior french drain idea and think it is a lot of work and creates its own set of issues.

I would do this project in phases, and see how each step improves your situation.
1. Drainage improvements- less moisture intrusion? Wall movements?
2. Structural assessment and repair of the wall
3. Once you have gone through your wet season, re-evaluate your moisture situation. The US EPA suggested detail makes a lot of sense, I would like to know what Ron thinks of it.

 

[SteamBryan]

Oldestguy,
Thanks again for your advise.
If I use a foam sheet under the soil, Do I still need bentonite?
My property line is six feet. I am thinking of installing foam for the 6 feet.
Regards,
Bryan