Radiant heat tubing depth

Al Martin · Mar 12, 2009

Hello everyone,
Planning on going with radiant heat in my new shop when I pour the floor this Summer. How deep should I install it? Was concerned with weight/stress mostly. Floor will be 6 inches. Heaviest item will be my 6x6 truck (13,000lbs.)

Thanks.
Al

BooUrns! · Mar 13, 2009

Hit up a library/ technical specs manual for proper installation instructions.

I don't imagine you're going to be able to suspend the pex in the concrete so it's going to have to sit on the bottom. Some insulation products for radiant (Insulworks) have channels in the styrofoam that help keep the loops straight during layout and while you place your slab.

tdkkart · Mar 13, 2009

Most people staple it to the foam, so that pretty much puts it on the bottom.

walrus · Mar 13, 2009

You put the tubing below the rebar or screen?

Ryan M · Mar 13, 2009

I attached mine to the top of the steel mesh. I had used R-foil underneath for insulation. On a 4"+ pour, it would end up around 2" inches below the surface.

Ezzie · Mar 13, 2009

At the risk of getting flamed, I don't think the screen is of any use as a floor "strengthener" - really only useful as something to attach the tubing to. Rebar is good, but really intended for floors/slabs where there is going to be a lot of weight moving around on it.

In my opinion, it is the best approach to fasten the tubing directly to the insulation board (SM, door cutouts, etc.) and then pour on top of it. The idea is to transfer heat from the fluid in the tubing into the slab.

Burl · Mar 13, 2009

Mine went like this: stone base, 2" thick extruded polystyrene Dow insulation board, 4 mil. plastic sheeting, steel mesh w/6" squares, then the tubing attached to the mesh w/plastic wire ties. If you get a piece of grid paper to lay your tubing design out on, you have the exact pattern with the steel mesh. It makes it foolproof.

sirswank · Mar 13, 2009

if you're concerned with weight, get a stronger concrete. standard concrete is generally 3000psi, which should be fine (13,000lbs / 6 wheels = 2167 lbs per wheel, and i'm fairly certain your tires have more than a 1 square inch footprint). however, 3500 and 4000 psi is available.

brad d · Mar 13, 2009

MIne was on top of the rebar that was on top of 6mm poly and 3" of SM..

walrus · Mar 13, 2009

Ezzie said:
At the risk of getting flamed, I don't think the screen is of any use as a floor "strengthener".

Concrete is only strong in compression, you can pull it apart. so what happens if you get a crack and it pulls apart without rebar or screen in it?. I'll tell ya, your radiant floor leaks like a sieve

5wndwcpe · Mar 13, 2009

Food for thought. If the tubing is stapled to the EPS, effectively putting it at the bottom of the slab, it's as far away from the surface as you can get. This way if you decide to run a 3" or 4" anchors for a grinder pedastel or such, you'll still have a margin for error. If you tie the tubing to the mesh, you better be damn sure you know exactly where that tubing is to avoid nailing it.

ScaldedDog · Mar 14, 2009

I had similar concerns, though I only have an 8000lb Excursion. I used 2" Dow High Load 40 (40psi vs. 25 psi for the regular stuff), wire mesh with the radiant tubing tied to the 6" squares, then 1/2" rebar on 2" chairs. 6+ inches of 4000psi concrete on top of that. One or two little superficial cracks, but I think it'll be plenty strong.

Mark

BooUrns! · Mar 15, 2009

IF your WWM (weldwire mesh) is on the bottom, it might as well not be there as it's not doing you any good unless it was suspended in the slab.

kvom · Mar 15, 2009

I ziptied mine to the rebar and it is in the center of the 4" slab. In any case, the slab will eventually attain a fairly constant temperature regardless of the depth of the tubing.

MyDomain · Mar 16, 2009

With that kind of weight do not use foam underneath. Use the thickest foam around the perimeter you can down as deep as you can so you don't have flowers blooming in the winter. The ground underneath the slab will form a heat sink. Use a product like http://www.houseneeds.com/shop/HeatingProducts/RadiantHeating/lotelmeshupsbuypage.asp to suspend mesh.

Radiant heat tubing depth

Al Martin

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tdkkart

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