Radiant Floor Heat - More Questions

I'm going to use 2" blue board insulation under the floor, but what's the best way to level the ground underneath? Voids under the insulation can't be good. Just spend some time getting the gravel base perfectly flat, or get really close, spread an inch of sand, tamp it, and screed again?

Next question, what's better attaching the pex to the insulation or to the wire mesh? I've read that it's more effective attached to the mesh, but it seems like it would be easier to install on the insulation.

One more, how many used the 25 psi rated board and haven't had problems? The Dow website list 40 psi as the minimum for foot traffic and 60 or 100 for anything more than that. I would think that the 40 is more than enough.

If you level it with a hand rake, anything after that the weight of the concrete will take care of pressing the foam board down.

I would follow the manufacturers recommendations, and not assume the PSI to use. I also do not think contractors get it perfect.

I like to lay the mesh down on the insulation and wire tie the PEX to the mesh, make sure the concrete works do not pick that up with the rake. The rebar should be spaced above the PEX. Other people like to staple the PEX to the insulation and skip the mesh.

Make sure it's POLYSTYRENE.. Pack your base really good put down at least 4" of sand pack it again. I thought in your other post you said you planned to run something really heavy on it. I would do what the manufacturer recommends as far as Psi. When I built mine I put reenforcing rod 1' from the outside edge all the way around then went 2'apart both ways to create a big checkerboard. Then the pex is fastened to the rods with plastic zip ties NOT wire.
Radiant heat

Radiant heat

Yes, meant zip ties.

Can't help on the insulation.
I've learned good and bad from mine, including no insulation under it that I already mentioned.
My land is clay. I let that settle for two years after building, leveling every year.
Then put in 4 inches of sand, leveled, watered and compacted multiple times.
What makes mine work well at all is probably at least in part due to the fact
that the tubing is not at the bottom where the insulation should be.
Mine has reinforcing rod ran in a checkerboard pattern, 2 ft squares, and every cross welded.
That checkerboard is centered between the top and bottom of the cement.
On top of that is heavy gauge 4x4 inch square "hog fence".
The tubing is on top of that fence, zip stripped down so it wouldn't float/move.
About an inch less to heat above than there is below the tube in a 6 inch floor.
I'm only heating 1024 sq ft here with 10 foot walls, but a standard
household water heater provides enough hot water to do it.

Well - we set up screed pipes, with the top of the pipe being the elevation of the finished floor. Then you can measure down from your screed (lying on the screed pipes) to your sub-base. The level of accuracy is up to you and your budget. Gravel/sand is cheaper than concrete, but don't get chintzy on floor thickness. I think one of your earlier posts mentioned some heavy equipment in your shop. We always used CA-6 or CA-10 for sub-base material. Lots of fines/moisture makes it compact well. No sand for us, but there's nothing wrong with sand. Tamp it good with a turtle, or something else suitable for compaction. We set the reinforcing on chairs, then zip tie the pex to the reinforcment. If you have a high tensile fence wire spool, or can borrow one, you can easily spool the pex tubing off of the fence wire spool. It eliminates a lot of fighting with kinks. The kinks want to stick up above your screed pipe, and will cause you problems when you're finishing the floor surface. Think about how you want to zone your floor. Is there any areas that you want to maintain a warmer temp than say a larger storage area? Zone your tubing so the temperature differential can be accomplished. Are you hiring a finisher, or are you experienced well enough to finish it yourself? If you're hiring a finisher (often money well spent) see if he will come out and give you some helpful tips. A good one will do that. I have no advice for the various PSI board ratings. Good luck with your project!

Paul

Just a warning, Pex will float if not tried down good.

Back in '97, our new house basement was leveled with a skidloader and front leveling attachment. Two inch blue styrofoam, then used cattle panels (6 inch squares) on top, and wired Pex to that. TOOK PICS so I can determine later where tubing is before walls are anchored to concrete.

If you're using mesh, it's a simple matter to tie your PEX to the mesh, the only disadvantage being the risk of getting the tubing too close to the surface where it could be cut when you saw your concrete. I don't know how well the clips that screw into the insulation work.

I packed my base down as good as I could with the tractor, then compacted the fill sand with a vibratory compactor. Seemed to turn out OK.

Screed it, tamp it, lay insulation, staple Wirsbo/ upinor to styrofoam, lift mesh when pouring. I wouldn't have the tubes fastened to the mesh.
good luck
k

My sister used cattle panels in there and zip tied pex to panels. LOT of bending over and took long time . I used 2 in high density foam and staples . They make a staple tool that uses plastic staples for pex . NO BENDING OVER and goes very fast ! Buy the tool and sell it on craigs list when done , or see if they have rental avail . Think it cost $200 ,,but I sold it for $190 within a week .