Expert: Richard Taylor, AIA - 4/11/2005

Question
We are building a house in an area with a lot of groundwater, (though no flooding), and want to know if we should do more than the typical level of waterproofing of the foundation.  Builders tell us two coats of the tar-like material typically used on foundations should be fine.  We have heard that there are other options, like plastic, that might be a better choice, and would like to find more information about these other options, and get a reccommendation about which are a good value.

Answer
Michael:

Waterproofing the foundation is NOT the place to skimp on quality or cost - you can't easily go back later and improve the waterproofing.

I suggest that you spend the extra money to install a "true" waterproofing system, such as Rub-R-Wall (www.rubrwall.com is the Ohio site) or Tuff-N-Dry (www.tuff-n-dri.com).  Both are waterproofing "systems" and are more expensive then bitumen (coal tar) waterproofing but well worth it!  These particular systems may not be available in your area, but you should be able to find something similar.

Waterproofing a foundation requires several techniques:
1) perforated drain tile inside AND outside of the foundation
2) gravel under the slab
3) several feet of gravel over the outside drain tile, with filter fabric over the drain tile (to keep the drain tile free of dirt)
4) waterproofing membrane on the foundation wall
5) protection board over the waterproofing (so it isn't damaged by backfilling)
6) finished grade sloped away from the foundation (it is up to the homeowner to maintain this condition after typical settling of the grade)
7) properly connected and maintained gutters and downspouts

The number one cause of basement water is disconnected or clogged downspouts; number two is settled grade around the foundation.  Keep these areas maintained to prevent a wet basement!

Hope this helps!

Richard Taylor, AIA
Richard Taylor Architects, LLC
www.rtastudio.com