Hello, I'm putting in floor radiant in my house right now. I want to put tile in my bathroom so what "layers" do I use. On the hardwood floor part of the house I'm using 3/4" subfloor, then 3/4" strips with aluminum plates in between, and then 3/4" hardwood. Right now the bathroom just has 3/4" plywood subfloor in it. Thanks!

For the bathroom floor you could use Warmboard or similar product. A thin Gypsum concrete slab is another good option too.

You are describing a sandwich system very similar to a product we manufacture and distribute RHT Floor Panel System.
Basically 8" pex pattern, 3/4" plywood heat transfer plate system designed for surface mount on sub floor. Turns, 1/2" pex, Omega heat transfer plates.
OK all that said when getting to a bathroom or kitchen tile portion of the house you have a couple options,
1/2" wonder board glued and screwed to the floor panel system, this is typical in high end construction, tiles are then thin set placed to the wonder board.
Alternately hold back the plywood and plates in the bathroom, roll the pex on pattern as you would fasten to the sub floor using large romesx wire staples
The reason for the romex staples is that the heads are thin, tube talons are about 3/16 and typically would be too tall.
Now with pipe down cover with concrete dry pack, a heavy on Portland cement, light on water stiff and strong mix. level cover with a isolation membrane like schluter membrane and away you go with the tiles.
Good luck,
Dan

Dan I actually am using your system for the house; it's great by the way. So I would just continue running it in the bathroom, put wonderboard on top of that, and then the tile? so that would be 3/4 subfloor, 3/4" strips, 1/2" wonderboard which gives me a total of 2" which would only give me 1/4" left for the thin set and tile.... Could I go smaller on the initial subfloor to make more room so the hardwood and tile are at the same level?

Hi, Glad to know you are using the RHT Floor panel system and that all is well.
Yes if you are looking for a way to keep a tighter control on floor transitions between wood and tile you can omit the wood and heat plates portion where there is tile as I mentioned and just lay the pex on the sub floor using the larger romex electric staples then concrete dry pack. Now you can control thickness. This method is good however you will need the isolation membrane as the concrete will crack on the pex lines, no harm to the pex but with out the membrane you will have crack transfer to the tiles.
Good luck,
Dan

Hi, Glad to know you are using the RHT Floor panel system and that all is well.
Yes if you are looking for a way to keep a tighter control on floor transitions between wood and tile you can omit the wood and heat plates portion where there is tile as I mentioned and just lay the pex on the sub floor using the larger romex electric staples then concrete dry pack. Now you can control thickness. This method is good however you will need the isolation membrane as the concrete will crack on the pex lines, no harm to the pex but with out the membrane you will have crack transfer to the tiles.
Good luck,
Dan

Dan, that sounds a little out of my comfort zone. I know very little about concrete and other pourable media. I think I'm going to do a 5/8" T&G plywood subfloor, then do the 3/4 strips with your system, then 1/4" hardy backer board, then lay the tile. I should be able to fit that into the 2.25" window. I might add some joists to cut down on deflection as well to make sure nothing cracks. Also, do you recommend I run it into the shower floor as well? I know I'm supposed to keep it far away from the toilet to keep from possibly melting the wax seal.

Ok,
Sounds like you have a plan, add glue and screws under the backer board.
I would not worry about going under the shower.
Concrete is easy though, wheel barrel mix and add a shovel or 2 extra Portland cement,
A good trick is to use roofing nails every couple feet to set hight of pour (slab thickness) so with a 1" slab the nail is pounded in leaving 1" exposed.
These stay in place and serve as marker when you trowel the cement flat. Don't worry about pulling them out as you go.
But your plan will work fine.
Dan

I used the Blueridge sandwich for my floor, and what I did was just to construct the under tile exactly as the floating floor, then used Ditra for the tile areas. I used extra thinset under the Ditra, troweled it into the tubing to level it and improve conductivity, and then installed the tile using Ditra's instructions on top of it. The stackup height was almost identical between the tile/Ditra and engineered hardwood, and have had no failures in the 5 years since I installed it. I did build my floors about 4x code minimum for deflection (I hate bouncy floors, and it really doesn't take a lot more material to get there), so if you have a lot more deflection you might want to go a different route.