New Floor

[liverplum]

Morning Tilers.

Just a quick one.

A customer has a completely rotten set of floor boards in a bathroom that we want to tile on to.

Can I just replace the floorboards with 12mm ply and tile straight on to or would I be best to use hardibacker boards on top of that?

Does anyone ever recommend using DitraMatt rather than hardibacker? I've used it a couple of times and always found it pretty easy to use although a little expensive.

:20:

 

[diamondtiling]

What has caused the floorboards to rot so much? What condition are the joists in?
I would suspect that the joists will be affected as well, simply replacing the floor with ply may be covering up another more serious problem.

12 mm ply is too thin, 18mm as a minimum, primed on the underneath and sides before fitting.

 

[liverplum]

Diamond advice! :hurray:

I haven't had a chance to have a look at the joists yet and will mention this possibility to the customer - he has had the floor up though so he may have had a look. Will check.

What would you use to prime the 18mm ply?

 

[Alan.P]

Does anyone ever recommend using DitraMatt rather than hardibacker? I've used it a couple of times and always found it pretty easy to use although a little expensive.

:20:

Why would you use a decoupling membrane in place of a board ? 2 completely different uses. As for priming the ply, an sbr primer will do the job.

 

[diamondtiling]

You can use an acrylic bond that is available from Tilegiant.
If the floor is as rotten as you say I would have huge reservations about proceeding with the new floor until the problem has been sorted, there may be spores that will need treatment first. Strength should be added to the floor with extra noggins at 250mm centres.
I don't like the description of this floor one bit, its rare to find such damage without also finding an underlying problem.

 

[liverplum]

Why would you use a decoupling membrane in place of a board ? 2 completely different uses. As for priming the ply, an sbr primer will do the job.

Thanks Alan, that has cleared that up. I didn't fully appreicate why the Ditramatt was being used on those occasions but now realise as both occasions they were very old houses obviously with lots of structural movement...

Also thanks Diamond for your words of warning. I will make sure we get to the bottom of it before proceeding.

 

[Gazzatile]

Diamond is right just tiling could cause you even more problems down line if the joist are in poor condition putting the extra weight on them could cause floor to drop big problem

 

[doug boardley]

ditra matting is used as an un-coupling agent to counteract expansion stress, hardiebacker boards are used as a suitable tiling surface and add no structural strength to your substrate

 

[Stephen@Weber]

Anyone else sat through the Ditra talk where it explains it like a loose layer of sand?

 

[White Room]

They were explaining that the romans used to use a layer of sand before the put the mosaic down and using ditra as a comparison