underfloor heating with solid wood

[robinsonrobbo]

Hi this is my first post here so here goes,I am installing around 20m2 of solid flooring in my kitchen and have read a lot about the different methods re nailing,glueing and floating however i am wanting to put underfloor heating under half the flooring.

My questions are should i use underlay then heater then float flooring or just heater then fully glue?

any advice appreciated.

thanks chrisl

 

[mointainwalker]

Floating is not recommended with UFH as it interferes with heat transfer.

What kind - and thickness - of flooring are you considering ?

Are you considering electric or water UFH ?

 

[WoodYouLike]

Solid wood flooring is not recommended in UFH, too much risk of extreme shrinkage and cupping.
You're better of with wood-engineered, also because it's in a kitchen - more moist.

Most manufacturers indeed recommend fully bonding of the wood floor to the concrete when there's UFH involved, to prevent air-gaps. Here's more info on UFH and wooden flooring.

 

[robinsonrobbo]

thanks for replies it is 18mm thick by 90mm wide random ,length lacquered birch i think and the subfloor is chipboard flooring.I did read as long as the width of the planks are not more thann 5 times the thickness it should be fine? it is electric system
any ideas

 

[mointainwalker]

UFH should be covered witha cement screed to take the load and distribute the heat. You have not mentioned this.

You need some screed, so to have chipboard and 18 mm wood on top would be uneconomical as wood is an insulator.

If you have screed you don't need chipboard.

Have you done any investigation into this ?

 

[WoodYouLike]

Every UFH has its own method of sub/top floor, not just concrete/screed, but chipboard is definitely a no no.
You can't nail nor use modern adhesive on chipboard. Swap the chipboard for plywood if that's still possible, much better and you can glue down on it.

90mm wide solid boards could just be alright, just be aware during the real heating season it will shrink and gaps can appear between the boards.

 

[robinsonrobbo]

thanks for replies.we are thinking of scrapping the idea or ufh altogether after reading up on it and with this advice so just fitting the floor could i float it as the previous solid floor which was down was floated but the recent building work we had done it got damaged and had to be lifted,or do i have to ply the whole area which will affect heights and then insulate or not?.

any advice appreciated.

cheers chris

 

[WoodYouLike]

No, you can't float a wooden floor that has board narrower than 100 - 110mm. You either have to glue it down (not possible on chipboard), nail it down (not possible on chipboard) or use self-adhesive underlayment (Elastilon, beware of cheap copy-cats).

Read this too: Solid Floors - what to note

 

[robinsonrobbo]

thanks for your brilliant advice and time.I have decided to ply the entire area and glue it down as i dont have a hidden nailer what is the best adhesive to use or is nailing a better solution?just the thinnest ply will do?

cheers

 

[WoodYouLike]

Thickness of ply depends on levelness of your existing floor (floorboards?). The minimum I would go for is 6 or 8mm ply (WBP grade).
(If you plan to install ply directly onto the joists as new subfloor it has to be at least 18mm ply to make the construction load-bearing)

Mapei P990 is a good adhesive (flexible) plus use a correct notched trowel

 

[mac391]

You could have simply installed your UFH on top of woodchip with the correct insulation and maybe a 14-16mm engineered board. There is no problem, perfectly feasible and would work fine. So the answer to your original question robbo is YES.

Mountainwalker.. what are you on about ?? cement screed over electric UFH ??

If woodchip is laid over floor joists it's fine to secret nail on top using a 3 ply building paper between old and new floor, the only fixing points are the joists though and obviously excludes UFH.

 

[mointainwalker]

@mac391

Why, technically , do you find the concept of electric UFH and screed strange ? Have just re-read this thread and NOBODY has spoken of electric UFH mac391 so tell us why you have suddenly dived in with this, will you ?

That apart, in you last post you say:

You could have simply installed your UFH on top of woodchip with the correct insulation and maybe a 14-16mm engineered board. There is no problem, perfectly feasible and would work fine.


Are you suggesting that the engineered board is just sat directly on top of the heating elements with nothing else at all `? It certainly looks like it because you mention nothing else.

Can you tell us with what experience you make your comments ?

 

[mac391]

mointainwalker, i'm going to publicly offer 1000 apolgies to you my friend, just for me being an arse!! Having bumped into a floor layer i'd never met before in a pub lol, so a few beers were had!!, we got talking about UFH,, yes it was that exciting!! and we were on about zenaflex ( a 1mm electric UFH mat) so i totally forgot about the cable system when i steamed into your advice.. You are right of course about the screed (on top of cables) i was just on a mission about zenaflex. This stuff is made for a floating floor and can be installed on woodchip, there's no screed required and yes, you fit the new floor directly on top (with a 0.5mm moisture barrier) if necesarry.

My only saving grace here is that robbo did say it was electric UFH and i'd had 3 beers which then makes me the best fitter on the planet lol !! Anyway, my apologies once again and here's the link http://www.floorheatingonline.com/shop/pdf/Laminate & Carpet installation instructions.pdf