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We're having a house built in a rural mountain area where the
predominant composition of the soil is decomposed granite and a little
clay. Our house is a passive solar design and uses a rock floor (about
3 feet high, 2" rocks or gravel) over a water barrier. The floor of the
house is 4" thick reinforced concrete on top of the rock floor. Because
of concerns about ground water, a French drain was installed around the
perimeter of the house. In one room of the house, the concrete floor
shows signs of cracking (about 1/16" cracks with about 1/8" uplifting).
The design of the rock and floor and been approved by engineers and
been used many times by this builder with no structural problems. At
certain times of the year, a hole at one side of the house that is
deeper than the rock floor seems to have water in it which makes me
think that the ground water can rise and fall.
The contractor speculates that areas with a little more clay may have
swollen a bit and caused the uplifting. Does this seem likely? Is there
a way to control this type of uplifting? I realize it is hard to make
an assessment without seeing the site. What sort of professional should
we look for for advice?
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cracks in the slab
