Mixing Plywood and insulation boards

[CCV6]

Hi. I am laying floor heating over around 11m2 on a concrete floor. Overall area is 20m2 for cupboards and a utility room. I have bought enough insulation boards 6mm thick for the 11m2 and planned to use plywood to raise the rest.

1) Is it ok grouting plywood to the concrete floor?
2) I would like to use 9mm ply wood so that the 6mm insulation board and 3mm thick heat mats are roughly brought to the same level. Is this wise or should I use 6mm plywood and grout the missing 3 or 4mm?

Thoughts appreciated.

Colin.

 

[Gazzer]

Grouting plywood ?
9mm Plywood and underfloor heating ?
Sorry if this sounds harsh but, You have no idea what you are doing , do you ?

 

[Ollie02948]

Everyone needs a bit more info than that to help you. I would advise getting a professional tiler around to have a look as what you are saying is not correct.

 

[CCV6]

Thanks, here is a bit more info

1) When I say grouting I meant to say flexible tile adhesive..

2) The floor is concrete and I am using the manufacturers recommended insulation boards. 6mm thick as I have a height limitation. Boards will be stuck down using the manufacturers recommended flexible tile adhesive. Fixing screw were recommended against for that thickness of board.

3) The whole area is not having underfloor heating applied so the question is what is the best way to raise these areas without using the expensive insulation board? My preference was to use plywood. I can either screw this down on to the concrete or I can glue it down using the flexible tile adhesive.

4) Regard the heights - I am proposing 3mm adhesive, 6mm insulation board, heat mat is 4mm (including the adhesive to fill) and then a top layer of adhesive to hold the tile (8mm notch - on test the tile sank down to 4mm). So total 3+6+4+4+10= 27mm.

For the areas where there is no head tracing I was going to use plywood preferably 9mm so giving 3+9+5+10= 27mm.

What are the alternatives to fill the height?

 

[Gazzer]

Self levelling compound ?
Why are you filling in the UFH mat with adhesive ?
9mm ply is not suitable IMO.

 

[CCV6]

Why are you filling in the UFH mat with adhesive ?.

Manufactuers recommendation. They give you the choice of covering it with flexible tile adhesive or self leveling compound.

 

[bugs183]

Hiya.
You can't afford to cut corners on an u/f/h project like this. It's a largeish floor,so it's not going to be cheap, and if you've not done one before you can get into a right mess.
Why not just use 6mm insulated board everywhere, you're only saving a few quid, it's not worth the agro.
Don't buy the rubbishy foam stuff that some u/f/h stores sell, it's awful, cheap and brittle. Buy a quality board like Marmox.
Lay the mats, then the u/f/h cable/mats and then self level over all of the floor, this will keep this flat and protect the cable from ho spots and damage whilst tiling.

 

[bugs183]

You'll also need to stick the boards down with at least an 8mm trowel, this may press down to 3, but i guess 5 would be a better guess.

 

[Gazzer]

Manufactuers recommendation. They give you the choice of covering it with flexible tile adhesive or self leveling compound.

Yes but it will be very messy and hard to achieve a flat floor .

 

[CCV6]

Thanks for the advice.

Self leveling compound it is - never used it before but will take the advice.

The boards were expensive and appear good quality, certainly been using the jig saw to cut them and they have not broken up. "F-board" they have an about four or five EN stamps. Anyway too late now.

Tiles are all cut beautiful, just moved them all outside ...bottle going ..just want to get it right.

The bulk of the kitchen is covered by the insulation boards its just a 10 inch strip round the edge...will go with the self leveling to fill it rather than the ply.

The utility room and the cupboards would have like to use the insulation boards but the budgets blown hence the reason for not getting the tiler in...

What do you use to stop the self leveling compound running under the work tops. Is there a polystyrene dam strip that you can buy?