Bathroom wet UFH floor buildup

[Super_Paulie]

Evenin.

I'm onto planning my bathroom and looking for advice and general opinions, which will be ongoing...

Searching buildhub via Google seems to have gone by the wayside and I can't seem to word what I want in the site search so here I am. 

 

I'm going to extend my UFH to the small bathroom (3x3m) and I'm struggling to find the build-up that would be best. For info the bathroom doesn't really need it, putting it in just to take the edge off a cold floor when barefoot.

 

My initial plan is PIR between joists, pipes clipped to it (or spreaders). 

The original floorboards need to go, so this is where I'm struggling for info. 

Replace subfloor with chipboard/ply? Then if I want to tile, do I need to go over this with say 6mm cement board? Insulated tile backer is adding insulation that I don't need.

I assume I don't tile directly into the subfloor.

 

Cheers friends.

 

 

Edited 16 hours ago by Super_Paulie

[Nickfromwales]

9 minutes ago, Super_Paulie said:

Evenin.

I'm onto planning my bathroom and looking for advice and general opinions, which will be ongoing...

Searching buildhub via Google seems to have gone by the wayside and I can't seem to word what I want in the site search so here I am. 

 

I'm going to extend my UFH to the small bathroom (3x3m) and I'm struggling to find the build-up that would be best. For info the bathroom doesn't really need it, putting it in just to take the edge off a cold floor when barefoot.

 

My initial plan is PIR between joists, pipes clipped to it (or spreaders). 

The original floorboards need to go, so this is where I'm struggling for info. 

Replace subfloor with chipboard/ply? Then if I want to tile, do I need to go over this with say 6mm cement board? Insulated tile backer is adding insulation that I don't need.

I assume I don't tile directly into the subfloor.

 

Cheers friends.

 

 

Go for spreader plates, but allow some rockwool under them, atop the PIR, so the plates are sprung upwards slightly. Then, when you screw the 22mm P5 deck down there will always be great surface contact between the aluminium plates and the underside of the P5. Without this, the heat transfer suffers somewhat.

 

I've never used backer board and only ever 6mm or more of plywood (glued and screwed down) and then tile straight onto the ply. For 6mm ply and 22mm deck you use 25mm 4.0 x 25mm screws to lay the ply so you don't hit a pipe.

[Super_Paulie]

13 minutes ago, Nickfromwales said:

Go for spreader plates, but allow some rockwool under them, atop the PIR, so the plates are sprung upwards slightly. Then, when you screw the 22mm P5 deck down there will always be great surface contact between the aluminium plates and the underside of the P5. Without this, the heat transfer suffers somewhat.

 

I've never used backer board and only ever 6mm or more of plywood (glued and screwed down) and then tile straight onto the ply. For 6mm ply and 22mm deck you use 25mm 4.0 x 25mm screws to lay the ply so you don't hit a pipe.

 

That's what I did in my porch, just forced the chipboard down onto the fibre-bouncy spreaders 👍

 

Thanks Nick, appreciate the info. Any reason for 6mm ply as opposed to a cement based board? I'm thinking for heat transfer.

[Nickfromwales]

39 minutes ago, Super_Paulie said:

 

That's what I did in my porch, just forced the chipboard down onto the fibre-bouncy spreaders 👍

 

Thanks Nick, appreciate the info. Any reason for 6mm ply as opposed to a cement based board? I'm thinking for heat transfer.

I just don't like the brittle nature, and I've done UFH with P5 + plywood so many times with great results, I just don't want to change. If it works, then happy days, plus the plywood conforms to the floor shape / undulations, whereas cement board will just snap or fracture, no Bueno afaic, sorry!

[Super_Paulie]

8 hours ago, Nickfromwales said:

I just don't like the brittle nature, and I've done UFH with P5 + plywood so many times with great results, I just don't want to change. If it works, then happy days, plus the plywood conforms to the floor shape / undulations, whereas cement board will just snap or fracture, no Bueno afaic, sorry!

i wont argue with that experience, thanks Nick.

Just so im on the same page, i always thought the ply screwed over the subfloor was so that if it needs to come up in the future then you dont have to destroy the subfloor. Surely gluing the ply to the subfloor will make that impossible? 
I assume im just overthinking this.

[Nickfromwales]

4 hours ago, Super_Paulie said:

i wont argue with that experience, thanks Nick.

Just so im on the same page, i always thought the ply screwed over the subfloor was so that if it needs to come up in the future then you dont have to destroy the subfloor. Surely gluing the ply to the subfloor will make that impossible? 
I assume im just overthinking this.

Yup. Let’s be honest, if you’re ‘accessing’ the plywood you’ve smashed all the tiles up and binning them so are ‘all in’. 
 

If you want the tiles to stay down, you go ‘all in’ on the installation and enjoy the longevity.

 

You could always fit 27, randomly positioned access panels on the ceiling downstairs.