Tile back/insulation board over floor boards?

[RickyLee53]

Hello,

I'm using tile backer insulation boards for underfloor heating upstairs. However half of the floor is new, (WBP ply) the rest is exsisting floor boards. They have years of varnish on them and are in sound condition. The area is approx 11 sqm, and i'd rather not remove them if possible.

Obviously I have been told to bed the insulation boards on flexi ady and screw to joists every 300mm. My question is, can I use the adhesive on the normal floor boards? Or should I cover the whole floor with another layer of ply/hardboard first?

I have sealed the top and edges of the WBP ply, but not the floor as of yet as its varnished.

Regards
Ricky.

 

[White Room]

I would fit on top of floorboards but make sure theres no bounce, also I would scratch the floor with a very course sanding paper to allow the adhesive to get some grip....

 

[RickyLee53]

Many thanks for your advise, there isn't any bounce on the old boards as there is a partition wall downstairs in the centre of the joists.

That was going to be my next question. I'm guessing once keyed, i'll need to seal the boards? Is it the moisture from the adhesive that gives you the issues with boarding over floorboards?

I would fit on top of floorboards but make sure theres no bounce, also I would scratch the floor with a very course sanding paper to allow the adhesive to get some grip....

 

[Alan.P]

You should seal / prime the underside and edges of the boards, this is to stop any ingress of moisture, prime the top ( working side ) if your adhesive manufacturer tells you to, I would prime as a matter of course if I wasn't using a rapid set adhesive.

 

[RickyLee53]

You should seal / prime the underside and edges of the boards, this is to stop any ingress of moisture, prime the top ( working side ) if your adhesive manufacturer tells you to, I would prime as a matter of course if I wasn't using a rapid set adhesive.

I have an S2 rapid flexible adhesive.

 

[Alan.P]

I have an S2 rapid flexible adhesive.

Which one, if you read the instructions on the back it should tell you.

 

[RickyLee53]

Which one, if you read the instructions on the back it should tell you.

Mapei I think its called.