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Re: Have you heard of watering your foundation?

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In Calif. we have several areas of highly expansive soils. The following
are some of the things we do to control extensive volume changes:
Overexcavate and recompact the soil  under the slab-on-grade at optimum
moisture (this means a day or two of watering the subgrade), heavily
reinforcing the slab, heavily reinforcing and deepening the preimeter
wall/footing, placing gutters and downspouts all around and keeping
landscaping away from the house.
Curing the concrete by water, a membrane or some other method is a
completely different matter.

Stan Scholl, P.E.
Laguna Beach, CA

On Mon, 18 Nov 2002 13:05:58 -0600 "Eric Green" <EGreen(--nospam--at)>
> 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)] 
> Sent: Monday, November 18, 2002 10:47 AM
> To: 'seaint(--nospam--at)'
> 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 

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