Is there a definitive answer on the best material to stiffen a floor before tiling?

[Hack 73]

Hi All,
Im about to put down some floor covering for a tiler to tile onto but it would seem they all want different things. Advice on the best thing to use would be much appreciated.

It's an upstairs bathroom so the tiles will be going over a timber floor. Electric heating mats are then being stuck over the top then tiles laid directly on top.

One guy advised 9mm another 12mm exterior ply and the third Knauf Aquapanel Water Resistant Wall Board 1200 x 900 x 12.5mm cement board.

Is there a definitive answer ?



Thanks in advance

 

[r1flyguy]

Treat the ply
Lay 10mm insulation board
Cover it with primer
Lay the mat, make sure you fit the sensor probe in a conduit
Cover with flexible self leveling compound

Ready & easier to tile

 

[Lower]

The definitive answer would be to lift the whole floor and replace with 25mm wbp ply it's noggins on all joints.

 

[Hack 73]

So if I went for the 25mm ply option could I just stick the mats down and tile over the top?

The manufacturer of the mats does say tiling directly over the top is no problem. The under floor heating is only used as a secondary heating source.

 

[L95]

I would just tile over the mats and make sure to use a plastic trowel to avoid nicks.

 

[Lower]

So if I went for the 25mm ply option could I just stick the mats down and tile over the top?

The manufacturer of the mats does say tiling directly over the top is no problem. The under floor heating is only used as a secondary heating source.

I believe so, yes.

The ply is there to give you a stiff floor to avoid tiles cracking. The theory is that if you overboard planks or chipboard with 12mm ply then you will end up with a stiff floor, but it depends on the strength of the original floor boards and you also end up with a 12mm step. If you lift the original boards and replace the whole lot with 25mm ply, you are going to get a very stiff floor and probably no step. The electric underfloor heating mat can go on pretty much any substrate.

 

[Lee@TileTown]

oh no, ive seen so many no nos in this thread.

first fix a thermal tile backer board, like wedi/marmox or Delta. 10mm thick.

lay ufh heating mats, but dont tile directly ontop of mats.......its not best practice......lay a self levelling compound over matting, you can buy one now thats ready to tile in 45 mins. then fix tiles.

 

[Hack 73]

oh no, ive seen so many no nos in this thread.

first fix a thermal tile backer board, like wedi/marmox or Delta. 10mm thick.

lay ufh heating mats, but dont tile directly ontop of mats.......its not best practice......lay a self levelling compound over matting, you can buy one now thats ready to tile in 45 mins. then fix tiles.

Hi Lee, thanks for that. Could I lay 12.5mm Knaff concrete aqua board/ tile backers board as the backer board followed by mats then self levelling compound?

 

[Lee@TileTown]

i dont know the Knaff product in question @Hack 73 so maybe best to ask them? If its a thermal tile back board then yes.

 

[r1flyguy]

oh no, ive seen so many no nos in this thread.

first fix a thermal tile backer board, like wedi/marmox or Delta. 10mm thick.

lay ufh heating mats, but dont tile directly ontop of mats.......its not best practice......lay a self levelling compound over matting, you can buy one now thats ready to tile in 45 mins. then fix tiles.

I think thats what i said!!!

 

[Hack 73]

oh no, ive seen so many no nos in this thread.

first fix a thermal tile backer board, like wedi/marmox or Delta. 10mm thick.

lay ufh heating mats, but dont tile directly ontop of mats.......its not best practice......lay a self levelling compound over matting, you can buy one now thats ready to tile in 45 mins. then fix tiles.

I think thats what i said!!!

Ok thanks both! And just to confirm floor boards with the board over the top will be structurally sound. It's currently on sale at Wickes so it works out cheaper than ply.

 

[r1flyguy]

As long as your floor boards are solid you should be fine

Where in the country are you? I have some primer & seal left over from my job you could have unless they included it when you purchased the matts?

 

[L95]

Out of curiosity Lee, have you seen that new anti crack matting with UFH installed into it?

OP I would agree that putting down some thermal boards would be a good idea.

 

[Hack 73]

As long as your floor boards are solid you should be fine

Where in the country are you? I have some primer & seal left over from my job you could have unless they included it when you purchased the matts?

Cambridgeshire, It was all included but the offer is much appreciated

 

[r1flyguy]

Thermal boards are more a necessity than a good idea I believe.

Just be mindful,
10 mm thermal board
7-8mm Matt & levelling compound
5mm tile adhesive
10mm tile

These rough additions will raise your floor level so you may/will have a threshold difference to compensate for