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RE: Have you heard of watering your foundation?

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Bruce:
 
I have lived in Dallas for more than 30 years.  As Davis and Jay have already written, watering our house foundations is standard practice here.  More specifically, watering the soil at the foundation perimeter is standard practice.  We have highly expansive clay soils and extended seasons with and without rainfall.  Less than 2% of houses have basements.  Most residential foundations are slab-on-grade.  Thus, our problems are severe. 
 
Clay soils only shrink/swell when their moisture content changes, so the goal is to keep the moisture content in the active zone (top 7-12 ft.) as constant as possible.  Keeping the soil "dry" is impossible due to our infrequent but significant rains.  On the other hand, keeping the soil "wet/moist/saturated" is more-or-less possible with diligent watering.  The most effective way of doing this is with buried soaker hoses continuously connected to a water supply.  Surface watering also helps, but is far less effective.  If a house foundation slab was originally constructed on dry soil (in August, for example) then watering might do more harm than good.
 
Most of our houses have brick veneer.  Brick is brittle, so most houses eventually have unsightly cracks.  Being in the South, they also eventually have termites.  We cheerfully put up with these and other nuisances, however, for the great privilege of living in Dallas and rooting on the #1 Stars and #1 Mavericks!
 
Regards,
 
Stan R. Caldwell, P.E.    
 
-----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