Hi all

Will be attempting a ufh install in a first floor bathroom soon. From my research I think I have it planned but am just checking I am doing the right thing. Any advice welcome.

The customer is keen to limit the raise in the floor so I am trying to keep everything down.

* Timber joists (these have had noggings added to reduce movement)
* 18mm T&G chipboard flooring
* 6mm ply screwed every 150mm
* 6mm marmox insulation fixed with flexible adhesive and washers/screws
* UFH (150w)
* SLC
* Porcelain tiles fixed with flexible adhesive

Question? I understand the ply will need to be primed, what product would be recommended for this installation?

In an ideal world I would prefer a thicker ply but customer is adamant this would increase the floor too much.

Is there anything else I have forgotten?

thanks for your time

just off to look at UHEAT for the matting......

regards franc

as for the primer most on here will say the underside and sides of the chipboard will need priming but i guess you're not able to do that? as long as the chipboards are solid you will be fine. also i'd use a 12mm backer board instead of 2 x 6mm boards.

if you're sure that the floor is deflection free dispense with the 6mm ply, way too thin.

Originally Posted by doug boardley

if you're sure that the floor is deflection free dispense with the 6mm ply, way too thin.

hi,

I was going to use the ply as I thought tile adhesive over chipboard was frowned upon. I am aware there are treatments that can be applied to chipboard to receive adhesive but most impressions i have seen advise against it.

regards franc

What area is the floor ? if I'm reading right your going to fit the T&G boards ? I would do away with the chipboard, lay 18mm min wbp ply then insulation boards then heating and slc, this will reduce the height and increase the efficiently of the heating.

Originally Posted by mikefiesta

as for the primer most on here will say the underside and sides of the chipboard will need priming but i guess you're not able to do that? as long as the chipboards are solid you will be fine. also i'd use a 12mm backer board instead of 2 x 6mm boards.

Hi

I can understand the thinking behind your method but priming all sides of the chipboard is impossible now. Using 12mm BB instead of the ply and insulation would further strenghten the floor and might be the way to go. Are you saying fix the BB straight to the primed chipboard?


regards franc

Originally Posted by Alan.P

What area is the floor ? if I'm reading right your going to fit the T&G boards ? I would do away with the chipboard, lay 18mm min wbp ply then insulation boards then heating and slc, this will reduce the height and increase the efficiently of the heating.

The bathroom is 1.4m x 2.7m. A 1700x700 bath, a back-to-wall wc with a concealed cistern in boxing and a vanity unit for the basin only leaves around 1.5m2 of tiles to warm/heat. The UFH was an afterthought. If I knew I would have put down 22mm ply in the bathroom area.

regards Franc

yes i would put the backer boards straight on the chip board , with flexi adhesive and screwed at 150 centres as in your original plan. make sure the chipboard is screwed down well , put more screws in if necessary but make sure you know where the pipes are in case you hit one.