How far apart should the rows of pex tubing be, and how far below concrete surface?
Should insulation be placed below the concrete?
You should be using Rigid insulation below then vapour barrier, then pipes at a min of 12" apart and max 2'...Use 1' pipe saddles so that when you pour your cement slab the pipes will be around the middle of the concrete.
The spacing is a little more complicated as there is a formula for area vs sq footage,and height of ceiling etc...but if you are doing the work, you should still consult your local municipality for pipe placement and insulation requirement...they may vary from City to City.
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