Messages and Online Forum Q&A

Re: foundation waterproofing techniques

From: info@builderswebsource.com
Category: Foundations and Basements
Remote Name: 63.198.181.43
Date: 07 Mar 2001
Time: 10:29 PM

Comments

1) Owens Corning manufactures a product called InsulDrain, which is an EPS insulating panel (4x8) with drainage channels and protective fabric netting to prevent soil contamination. Product information is available at:

http://www.owenscorning.com/comminsul/products.asp?product=26&system=82

2) We are not aware of a channeled EPS foam product which also contains termite control. EPS by itself does not provide nutrient value to insects. However, the "warm area" created by EPS insulating foam can hide insects and provide a convenient transport path. Termite and insect control must be looked at as a total system, which may also include periodic soil treatment in heavily infested areas. According to Owens Corning:

"In areas with potentially heavy termite infestation, check local building codes regarding the below grade use of foam insulation. Foamular insulation does not attract insects or provide nutritional value. Infestation is a random event.

Foam insulation may provide a soft media that conceals insect tunneling. In areas of infestation, the following preventative measures may be appropriate: pre and post construction treatment of the soil, termite shields, and wrapping EIFS around the foal insulation edges to reduce exposed insulation surfaces.

It may be appropriate to terminate EIFS 6" above grade, providing a gap in the insulation to inspect for termite tunneling. Termite baiting systems in conjunction with regular professional inspection have also been proven effective at eliminating termite colonies."

3) A keyed foundation means that the concrete footing has a "beveled key" running along the center of the entire footing (where the vertical rebar sticks up). This is usually made with a beveled 2x4 - which is later removed prior to building the wall itself. When a concrete stem wall or CMUs are placed on top of the key (later filled with grout)...and when the key has a water guard in place, the wall will positively lock into place and provide a moisture barrier due to the key. The detailing of this is important and any competent engineer or contractor should understand how to do this.

4) With respect to your drainage tile question, I'm not sure I fully understood the issue. The important point is to place the exterior french drain pipe with holes facing DOWN. The level of the holes should be well BELOW the top of the footing, otherwise the water level in the french drain ditch could rise ABOVE the level of the footing -- which will result in possible leaking inside the basement. If interior drainage is required, this should be designed so as to prevent any backflow from flooding underneath the basement slab.

5) Finally, if you live in a particularly cold climate -- or if you have radiant floor heating in the basement slab, using EPS under the slab is a good idea. Products such as R-control or Owens Corning Foamular are fine for this application. For example, Foamular 250, which is designed for residential and light commercial applications, has a compressive strength of 25 psi. Assuming the subgrade is properly compacted and covered with a 6 mil or thicker vapor barrier, you shouldn't experience and problem with your concrete slab. The exception to this is if you have highly expansive clay soil, where upheaving could crack the slab. In this case, check out products from Beaver Plastics at http://www.beaverplastics.com which are designed to gracefully compress when exposed to expanding soils. This product works with structural slabs.

To provide extra insurance, be sure your slab has plenty of rebar reinforcement (at least #4 bars on 12" or 16" centers each way). And if you really want to help prevent cracks, use Fibermesh with the slab. These are tiny fibers that provide secondary crack reinforcement and only add a few dollars of cost per yard of concrete. This stuff is great when used properly.

We hope this answers your questions. Good luck on your project.

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