Messages and Online Forum Q&A

Re: foundation techniques continued

From: info@builderswebsource.com
Category: Foundations and Basements
Remote Name: 63.198.181.43
Date: 11 Mar 2001
Time: 04:43 PM

Comments

Thank you for the detailed summary of your conditions. Clearly there are specific local codes dictating the best practices in your area with respect to foundation drainage. During previous posts regarding your project, we have outlined generally recommended methods for drainage, but we always advise that you consult a local engineer who is familiar with the codes and specific site conditions.

The concept of "hollow" CMUs as the first course of your basement wall is not something we would generally recommend. This not only weakens the structural joint between the footing and the basement wall, but it would seem to provide an opportunity for moisture to penetrate into your basement. Faxing or mailing a detail or cross-sectional view might help us to better understand the proposed configuration in case we have misinterpreted your description (which is always possible when communicating without drawings). However, generally the key is to build a solid wall with proper exterior waterproofing that prevents moisture from penetrating the structure in the first place. If done properly, you shouldn't have any problem.

With respect to the local code requiring that the french drain is above the footing, this goes against most common practices. In your case, the key is to be sure that the water level in the trench is never ABOVE that of the interior slab...and ideally well below it. Anytime exterior water levels are above the interior slab, hydrostatic pressure can result in water seepage through the smallest of cracks, resulting in a damp basement floor.

We would strongly advise that you work with a licensed civil engineer with expertise in foundation and drainage design to ensure that the combined system is being properly designed and installed. The incremental cost of doing it right now is way smaller than the cost of a wet basement in the future.

Good luck with your project and keep us posted on your development.

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