Basement waterproofing

robsb123January 23, 2008

I just bought my home, in Northern Kentucky, about 4 months ago and I am planning on refinishing the basement into a rec room. The house is 10 years old, and there are about a dozen hairline cracks in the walls (nothing wider than 1/32"). The floor is in good shape, although it doesn't pitch toward the drain very well. I have never seen the walls or floor leak since I have lived there, and it has been pretty wet outside at times. I can't see any evidence of leaks. There is no efflorescence or water marks on the walls, and the air feels dry. I was considering using a product such as drylock to seal the walls and hopefully the cracks. I have the following questions regarding the sealing and insulating of the basement.

1) Is drylock (or any sealant) effective for sealing hairline cracks, or do I need to chisel out the cracks and fill them in with hydraulic cement, or some type of caulking?

2)Should I seal all of the walls and floor?

3) If I seal the walls do I need to use XPS (or EPS) on the walls, if so what is the minumum recommended thickness?

4) Should I use faceless fiberglass insulation between the studs? Should I leave a gap between the studs and the XPS?

Thanks for your help.

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Check past threads.

Hairline cracks are normal. My preference is for a crystalline waterproofing product, which reacts with moisture to seal the concrete, including hairline cracks. It is permanent and doesn't flake off.

The mixture of EPS/XPS to fiberglass (if at all) is a matter of economics and personal preferences. R5 boards on the walls should be sufficient to virtually eliminate condensation problems.

If you're doing wood or metal framing, be sure to put he baseplate on a 1" strip of XPS; just anchor the plate through it to the floor. No gap between the studs and the XPS. Air circulation is not a desirable feature in any insulated wall.

Here is a link that might be useful: Foundations/Renovating Your Basement

    Bookmark   January 23, 2008 at 12:40PM
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Do you think that it is a waste of time and money to paint the walls and floor? There has been a piece of vinyl flooring laying on the basement floor since I moved in, and I occasionally lift it up to see if there is any moisture under it. There hasn't been any moisture yet.

Will putting XPS on the wall do anything for Radon. I just got the results back yesterday for a DIY radon test and it came back at 2.1 picoCuries/Liter. This is supposedly in the "safe zone" but still above average. I was wondering what can be done to lower this number further.

Can you give any specific crystaline waterproofing products, and tell me where to get them?

If I am going to put down carpet or laminate flooring, what means should I take to waterproof the floor?


    Bookmark   January 24, 2008 at 1:25PM
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I've never bothered with the floor. As for the walls, if they're dry after ten years it may be unnecessary. Crystalline waterproofing bridges all the little shrinkage cracks and fissures. But if a settlement crack wider than 1/64" develops through the wall, it's not effective. That's why most new homebuilders here use an external membrane, usually a plastic dimpled type that bridges the entire wall. (There's a mandatory two-year warranty against water penetration in Ontario.)

I've used Permaquick products in the past. But when I spoke with them last year they were only selling it to qualified applicators. Before applying the coating, the wall must be washed in sulfuric acid. I suspect they fear liability problems if they sell to the general public.

I think the permeability of XPS would not make it useful as a radon barrier. Radon can be reduced by venting and sealing. 1, 2 Before undertaking expensive measures to reduce radon, you might want to take another test to be sure.

carpet or laminate flooring

Laminate flooring manufacturers say their product is suitable for basements. I even saw a new home that sold in November for $1.998 million that had a basement in laminate. However, I wouldn't use it. Aside from the ever present risk of liquid water, water vapour is constantly moving through the floor due to pressure differentials. I doubt the builder used a capillary break to prevent this. However, there is one laminate,Icore,that addresses the issue by using an entirely synthetic backing.

I've used carpet successfully for 20 years on my homes. But I only put in low-pile, preferably jute backed, carpeting through which the water vapour can freely move.

Whatever you use, Building Science recommends mechanical dehumidfication to keep the relative humidity low, especially during the summer.

    Bookmark   January 24, 2008 at 9:52PM
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