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Water table

don_185
don_185 Member Posts: 312
When to design for high water table on a radiant floor job
and,how would you know?

Lets say a house is being built near the oceanfront and very close to the water.Do you assume that it has a high water table? And at what depth does it no longer become a issue.

Is it or, would it still be a issue with a thermal break?

TIA.

Comments

  • Brad White_185
    Brad White_185 Member Posts: 265
    Water does

    as it dang well pleases..

    The elevation only affects the water table slightly and there are a lot of variables. Ground water flows uphill in many circumstances by what are known as "matrix forces". Think how you drop a sponge in a shallow spill and how it wicks up? That is the same principle.

    To determine the water table you need to dig a well hole and wait. Well, I mean, go about your life and all... just take note of how high it is seasonally. Some places are "spring high" or just during rain (say you have a lot of clay). Other places are dry year-round.

    Unless I was convinced that there was a low water table, I would assume and prepare for some intrusion.

    Moisture greatly affects the conductivity of soil so yes, more insulation would be in order, over your vapor barrier. If you have a legitimately high water table (and some hydraulic up-lift!) a structural engineer should be consulted. A mat-slab or mud slab may be in order to suppress the hydraulics.

    My $0.02

    Brad
  • Floyd_50
    Floyd_50 Member Posts: 8
    That is why...

    You always insist on good perimeter drainage and gravel under your floor, to make sure that no water can backup or accumulate under the slab.
    I often wondered how a spring can bubble out of the top of a mountain...an awesome site to follow a creek to the top of the mountain, only to see the pool that starts it all bubbling up at the highest point or nearly so.
    Matrix forces... huh...always learnin' here...

    Floyd
  • don_185
    don_185 Member Posts: 312
    Maybe

    Maybe, I would be better off watching the tide roll in.

    Thanks for the reply..now I have to go look up matrix forces.









  • Darrell
    Darrell Member Posts: 303


    I take care of a house that has a well that is artisian only at high tide...actually about 45 minutes off high tide. This well is twenty miles from tide water at 250 feet elevation above mean sea level and the water is clear and sweet. The pressure at high tide is about 10psi and runs about 4gpm. In the summer she waters her huge garden with the outflow. In the winter she has a periodic fountain that makes really cool ice sculptures!

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