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RE: Have you heard of watering your foundation?

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The clay soils found in Dallas, Houston, Austin, San Antonio and Beaumont experience significant changes in volume with changes in moisture content. The amount of movement at the surface can be as large as 9-12 inches in severe circumstances, but is generally less. Seasonal movement is a problem because the soil generally looses moisture in the hot, dry summer and gains moisture in the cool, wet winter. This seasonal movement can cause problems such as sticking door and windows and drywall and brick cracking. The idea behind watering the foundation is to prevent seasonal movement by keeping the moisture content at a constant level. However, it is unlikely that this will prevent all movement as is it difficult or impossible to truly keep the moisture content (mc) constant. It is possible to reduce variations and seasonal shrink-swell.

 

Grading is important for the converse. Just as you water to keep to soil from getting too dry, good drainage can be important to keep it from getting too wet. The key is consistency.

 

Long term movement due to other causes, such as construction during exceptionally wet or dry periods, or growth of a large tree near the foundation, are generally not going to be prevented by watering the perimeter of the house.

 

Eric Green

 

-----Original Message-----
From: Trobridge, Bruce [mailto:Bruce.Trobridge(--nospam--at)ogs.state.ny.us]
Sent: Monday, November 18, 2002 10:47 AM
To: 'seaint(--nospam--at)seaint.org'
Subject: Have you heard of watering your foundation?

 

I was asked this question by my brother who is building a house in the Dallas area. I am a structural engineer in New York state and my response was- What? Why? I have not heard of this practice and neither has anyone I work with. The people he has spoken to (who are not engineers) say that if you don't water the concrete it somehow loses strength and cracks. The only thing I can figure is that the clay soil there has not been preconsolidated by glaciers as it has here and the moisture is kept up to prevent consolidation and settlement of the house. Am I on the right track?

Bruce C. Trobridge PE
Senior Building Structural Engineer
NYS - Office of General Services
(518) 486-1749