Retro fit radiant floor heating

[theoldwizard1]

Has anyone done this ?

Of course there is no insulation under the slab so at least 1" - 2" of foam board must be laid down. There will be no vehicles parked on top, so could you do a 3/4" plywood floor over a 4'x4' grid of 2"x4" PT sleepers on edge ? The bonus of this would be a flat floor (it is sloped for in floor drains).

The goal is to turn an old commercial building into comfortable office space.

 

[Kaizen]

Doable. I’d do the two inch. But you will then have to use those subfloor panels that the pex gets hammered into. Then the ply on top of that. Also would have to figure out where sleepers were to screw the ply to without hitting pex. Might be cheaper to use two inch insulation. Secure pex to the foam. Then lay a one inch or so layer of gypcrete that encases the pex. It flows like water but needs a pro with a truck that does it and pumps it in. Remember any code issues at wall outlets and grade change at door


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[engineer2]

Did it in my basement 14 years ago. Been working great ever since.

1/4" fanfold on the floor, 3/4" plywood sleepers cut to fit the PEX tubing. Plywood is power nailed to the floor. Heat transfer plates made out of aluminum flashing. Floating glue-less laminate flooring on top.
Now they have kits to route the tubing, so you can do partial plywood and use the "Easy Floor Grids" for the turns. I could have gone with ticker foam underneath, but the additional floor thickness would have cause issues with doors and stairs.

The system consumes about 20 BTU/sqft and my feet are nice and toasty as I sit here in the basement.

 

[raspy]

An easy and foolproof way to do it is to lay down a layer of Blueboard, attach the tubing to that insulation board and then pour a thin concrete slab to the level you want. It will also level out any slope.

If your floor is dry underneath, meaning no groundwater, just shoot down 6-10 mesh and tie the tubing directly to that. Hold the heat back from the edges by 1-2 feet. Pour the slab and then add any finish flooring you want.

Unless you have a very large or complicated floorplan, you should be able to lay all tubing in one day and pour the next.