18mm wbp ply

[Gazebo]

Morning all,

I know this has been answered lots of times and I have spent the last hour or so reading old posts, (still confused)

I have a 2.8m x 1.4m bathroom suspended bathroom floor to tile.
I have removed flooboards and put in lots of additional noggins and then fixed down 18 wbp ply. I am trying to keep the height down.
Now the floor is down I have concerns that is should have been 25mm wbp.
Is 18mm wbp ply thick enough.??( I have sealed underside and edges with primer g before fitting)
The floor is very stable.
My next step is to install elec ufh.
Then mapei fibreplan slc
Then 450x450 porcelain tiles (obviously with a spf adhesive)

Should i overboard ply with some kind of insualtion board prior to ufh.
Will this help with any minor deflection.?

Ideally I wouldn't use insulation board but if you guys think i should then i will, maybe if i use a 2 part flexi adhesive will this be better over the ply.?

Cheers for your help and Merry Christmas to you all.

 

[grumpygrouter]

With your size of floor I would think 18mm is perfectly adequate for strength, especially as you have noggined it. Persoanally, I don't like the idea of heating elements directly onto ply so I would put a 6mm insulatioin board down and then finish as you have suggested. The insulation is just a personal thing with me as I know it isn't really necessary. Just don't like the idea of direct heat onto timber.......

 

[diamondtiling]

Same as grumps for me.

 

[doug boardley]

as I was reading your post I was agreeing with the stages and materials, so thats a yes from me too

 

[Gazebo]

Thanks for the advice guys, so just to clarify.
Do i need to use 6mm insulation boards and do i need to use 2 part addy,?

1 or the other or both or a method you would choose.?

 

[Daveyboy]

Personally, I never use the insulation boards except on solid substrates and then only if I am unsure as to whether there is adequate insulation... Normally, I fit 12mm ply onto existing floorboarding and this is because I've found that it's not always possible to cut out all the floorboarding (some of the joists are sitting under the stud walls)... I always put ufh onto ply then slc over it... it has never let me down..

 

[diamondtiling]

Can see daveyboys point of view, I would use backer boards because there is no moisture whatsoever in them.

 

[tfs]

It would be better to use the board for reducing heat loss etc. I think it would be wise to use an S2 class adhesive (not all s2 adhesives are two part) for a little extra peice of mind with the floor.

 

[Gazebo]

:8:Thanks for your reply tfs, can you clarify which s2 addy is not 2 part.?

if I didnt go for the insulation board option, what slc would you use to cover the ufh mat and what addy and grout would you use to finish.?

:8:

 

[Matt]

Mapei Ultraflex (Mono or Quick) are a single part S2 adhesive. But, they are not receommended for bedding UFH heating into the adhesive.

Keraquick mixed with Latex Plus is an S2 adhesive and is fine for UFH.

 

[tfs]

Kerraquick with latex plus and for self levelling you could use Latex plan which is a 2 part slef levelling screed.

 

[tfs]

I would use Ultracolour plus grout