underfloor heating Engineered flooring subfloor with wet UFH

[SLinds]

I need advice on the best material to lay ontop of wet underfloor heating between existing joists to lay engineered parquet flooring.

 

Floor construction is made up of suspended timber floor with battons to support 70mm insulation board. UFH heating pipes then clipped to insulation and covered with 8:1 pug mix. My supplier of the engineered flooring (which is 15mm thick) recommended screw ply onto joists and then glue engineered flooring onto the ply, however I am worried that this will have a detrimental effect on the heating efficiency. Is there a better option to this or does it sound like the best option? And if so what thickness ply would be recommended?

 

Thanks

[Temp]

1 hour ago, SLinds said:

My supplier of the engineered flooring (which is 15mm thick) recommended screw ply onto joists and then glue engineered flooring onto the ply, however I am worried that this will have a detrimental effect on the heating efficiency. Is there a better option to this or does it sound like the best option? And if so what thickness ply would be recommended?

 

Got a feeling the Building Regs require 18mm minimum thickness for structural floor boards.  That's probably why he's saying to fit ply first. Your best bet is going to be to find 18-21mm thick Engineered flooring. 

 

In the case of carpet over UFH they recommend you keep the TOG value for the carpet and underlay below 2.0-2.5 total. Unfortunately I don't know how to translate that to mm of plywood. Just for info special low TOG underlay is available (0.6-0.7). Also carpet with hessian rather than rubber backing is lower TOG. Just watch out because some carpet is made in both versions and the carpet showrooms sometimes reserve the right to supply either in their T&Cs.

[ProDave]

I used 20mm thick engineered oak over battens at 400mm centres.

 

Can the OP confirm how the floor is made? "Parquet" to me means lots of individual pieces laid in a pattern, so cannot possibly be structural and needs to be laid on something.  If you mean is is an engineered structural board made to look like parquet then I suggest you look harder for something that can span on it's own as  a structural floor.

[SLinds]

10 hours ago, ProDave said:

Can the OP confirm how the floor is made?

 

The engineered flooring is made of lots of 120x600mm pieces in a herringbone pattern so no, I presume it will not be structural, although the pieces do fit together with tongue and grove.

[ProDave]

So that will want 18mm ply then as a structural floor if the joists are 400mm centres.  If 600mm centres that will need to be 22mm.

[Temp]

4 hours ago, SLinds said:

The engineered flooring is made of lots of 120x600mm pieces in a herringbone pattern so no, I presume it will not be structural, although the pieces do fit together with tongue and grove.

 

Have you already purchased it?

 

You can get 18mm (13mm ply, 5mm oak?) herringbone engineered flooring but I don't know if its rated as structural (eg for use without additional ply)...

 

https://www.saleflooringdirect.co.uk/item/794/EngineeredHardwoodFlooring/Engineered-Marrone-Brown-Herringbone.html

 

https://www.saleflooringdirect.co.uk/item/899/EngineeredHardwoodFlooring/Engineered-Oak-Herringbone-18mm-x-120mm.html

 

 

 

 

Edited June 30, 2020 by Temp

[Bitpipe]

Not exactly the same situation as you but...

 

I have a suspended timber ground floor over the basement. I used Alu spreader plates and they are just insulated underneath with rock wool and the basement pb ceiling. Structural floor is 18mm OSB (glue & screw). On top of that I have 9mm marine ply & cross laid 12mm ply all glued & nailed. On top of that is a 6mm rubber crumb mat and 6mm (3x2mm pours) of resin. There should only have been one 2mm pour of resin but it wouldn't cure properly so they did it two more times.

 

Quite a sandwich and just over 50mm of solid material but the heat passes through it all just fine - as our house is low energy design, the UFH flow temp is as low as the mixer will go - about 35^o I think.