Grading lawn

Published on December 6th, 2015 | by Henri


Vapor barrier under basement carpet

Q.  I enjoy reading your articles each week and now I have my own question. Our basement has flooded in the past with as much as 3″ of water. So our finished basement (done by the previous owner) was ruined. After we cleaned up the mess, we installed an interior french drain around the perimeter that feeds into a sump pump with a battery backup system.

Now we are ready to remodel and put down new flooring. Because of the history of the basement flooding, do you recommend us installing a vapor barrier (6 mil poly) over the concrete before the 1/2″ pad and carpet? I wonder if this is necessary or not. The large box stores have said that their Stainmaster elite pads are supposed to have a built in vapor barrier on the bottom. I wonder if this is sufficient or we should include the poly for added protection. Thanks!

A.   Has the source of the basement leakage been taken care of? This is the best way to prevent a recurrence.

Basement and crawlspace leakage is mostly due to grading problems around the house. In my experience over 60 years in the construction field, a very few cases of foundation leakage are caused by underground springs or a seasonal high water table brought about by snow melting in the spring or heavy rain events.
Grading problems include flat or negative grade that collect or allow water to pond near the foundation walls and percolate, or run down along the walls until a weak spot in the foundation is found. Negative slopes on walks, patios, porches, driveways, etc., are also factors.

If you have had several strong rain events as well as significant snowmelt, and have not experienced leakage, and the drain and pump system is doing its job, it should be OK to use the elite pad and not bother with a poly film, although there is no reason why you can’t use a 6-mil plastic sheet if you would like extra protection.

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