Hardy Backer board (6mm) OR ply (9mm) for my travertine??

[ferrisbueller]

Hi,
need some advice, as I'm getting a bit of conflicting advice.

I have a half concrete, half floorboard area of approx 46m2. Do I use hardy backer board (6mm) OR ply (9mm) as a base to prevent hairline cracks across the join ??

What do you pro's think?

PS We are using electric underfloor heating, should we use thermal board instead.

PPS we are insulating underneath the floorboards (between joists).

Would welcome some feedback soon as we need to make a decision

PPPS Thanks to Diamontiler for help a while back - we are going with the supplier we talked about - got some good quality for a decent price.

Thanks

 

[grumpygrouter]

You will need a movement joint across the point where the 2 substrates meet.

 

[david campbell]

never use ply less than 15mm,any less and the ply is not suitable due to moisture!

 

[ferrisbueller]

Firstly,

1. What is a movement joint?

and

2. Is backer board moisture proof, therefore better than ply??

Cheers

 

[diamondtiling]

see pm

 

[diamondtiling]

I spoke to Oscar the MD that you put me in contact with, he has very very good prices on trav/limestone etc and he guarantees they are the best in the uk or your money back.
cant say fairer than that.

by the way he beat my supplier by £10 per mtr.

:yikes:

 

[Rob Z]

Ferris, I like the screen name, loved the movie back in the 80's .


A movement joint is a "soft joint", designed to absorb movement and stresses in the substrate under the tile. A soft joint can be simply a space that is an unfilled grout line, then filled with a flexible sealant. Or, it can be a product designed for the purpose, such as Schluter Dilex. We have standards here in the US and Canada that we can follow for placement and width of movement joints-Dave or one of the guys here can post a reference for you of what the standards are to follow in the UK. They are fairly easy to follow and to implement.


Some backerboards, such as Wedi Board, are waterproof. Most backer boards are not affected by moisture, but aren't waterproof without a tanking membrane. Generally speaking, backer boards don't add strength to the assembly the way plywood does. If given the choice, I would add plywood for additional strength and then install a membrane to eliminate the potential for problems that might arise from bonding tile directly to plywood.