Marble / travertine.

[Rich]

Id always go with a backer board over ply given the choice.

 

[tonym]

So 12mm backer board instead of ply on the floor? Just out of interest can I ask why?? Would it be better adhesion for the backer board or greater stiffness ?

 

[Rich]

Of course you can.
Backer boards will not rot with moisture, if and moisture gets to the ply wood (through the grouting, Silicon or from underneith) it will swell and rot, this can stain the grout or even pop the tiles off. And you will get a better bond to a backer, I use 2-part on any wood, although most tilers will use a single part, to make sure but will happily use a single part on a backer board.

 

[tonym]

Do you think a double layer o0f 12mm backer board cross fixed with staggared joints would be overkill and is ther any difference in quality with the baker boards, or could you reccomend a backer board brand?

 

[Rich]

I use No More Ply but plenty of the guys on here use Hardie, to be honest I think they are pretty much the same thing, you can get thicker board if you need it, NMP goes up to 50mm. Why do you want to go so thick? Is there a lot of movement in the floor? What is on the floor at the moment?

 

[tonym]

Previously i had a porcelain floor put down. The floorboards were taken up (circa 1920's house) and was recommended 25 mm ply straight onto joists. This place is around the corner. Its my sisters house and considering the weight of the tile iI want to make it belt and braces, as I don't want her complaining a few years later.
There shouldn't be any movement in the floor considering its a new floor of a new loft conversion. There is nothing on the floor at the moment. It is just exposed 8x2" joists.

 

[Rich]

You could always lay ply then over lay with a backer board like NMP/Hardie, just make sure the floor is as solid as poss, adding extra noggins if needed and seal the underside and the sides of the Ply before laying.

 

[tonym]

thanks. Thats a good idea. Would the Bal Primer be good enough as a sealer for the Ply??

 

[Rich]

I couldnt tell you to be honest, as I said Im a Mapei man so Im not familiar with BAL products but you dont have to prime the NMP, you can dampen the boards with a sponge or rag before spreading your adhesive instead.

 

[paulc2012]

Hi guys,
just thought I'd stick my 2 penneth in.
I think I'd go for the ply - 18mm, marine grade, it's not cheap, but you can't go wrong. Remember it needs to be fixed at 150mm centres, so you need plenty of noggins. Any of the Bal primers will do in this situation, but my preference is an SBR, which Bal do also. A bit of a tip though, SBR is merely an acronym (Styrene Butadiene Rubber) and you can pick it up anywhere from a Large B+Q to your local builders merchants and probably a lot cheaper. Most are sold for theirwaterproofing and bonding qualities, so dilution is likely to be 1 part liquid to 3 parts water. Use it to seal the edges of the boards too.
If you were still worried about the waterproofing, I'd go for a waterproof membrane like Schluter Kerdi matting, which is thin (so without height implications) and is versatile enough to make up floor to wall skirting pieces, pipe collars etc, alternatively you can buy them ready made, but at a premium.
For the walls, 15 mm wedi or marmox (marmox is cheaper).
Last thing, don't believe the builder when he says the ply is waterproof unless he can show it to be marine grade. WBP (often said said to be waterproof)(WBP stands for water and boil proof) varies so much in it's standard, that problems can occur.
good luck
____________________
paulc2012
http://www.oakenstone.co.uk

 

[Rich]

Id like to add one thing, marine ply is not what most people think it is. It does not mean that it is suitable for wet areas, it means that it it guaranteed to have no gaps in it. So the ply MUST be water and boil proof.

 

[paulc2012]

Hi Dylante,
what a great thread, perhaps we should sit down and talk plywood over a beer. and watch everyone else drop around us (smirk). But you're right, there's no 'silver bullet'. The following link has some good comparative info on the extreme effective of different plys,
What is the best marine plywood - Boat Design Forums
but my previous post is just based on personal experience within construction.
When I first started in construction 20 years ago, there was no such thing as WBP, marine ply was the only ply recommended to be used for tiling on in a wet area situation, and we always found it to perform well (as long as you followed the correct guidance on fitting). Tiles always remained fixed. Even if you needed to go and put right someone else's badly installed work, where there may be a leak, or the work was just rough, you'd have a heck of a job removing the tiles.
When WBP came in, we started to see it used everywhere on site. People became over confident with it, and I remember on a few occasions where houses were being constructed during the winter months and progress was up to first floor, floor level, the WBP would be installed and construction would just carry on until the brickies hit the roof line, the chippies would come in, install the roof plate, then the roof and of course finally get a pre roof tile membrane on. All this time the WBP would be exposed to the elements, but it would take no time before you saw delamination and warping. On the tile fitting side, I have been called in to a number of bathrooms where the walls and floors were constructed out of WBP. The builders thought they were doing the right thing, as more alternatives came onto the market, and awareness grew that chipboard floors and plasterboard walls were no longer cutting it, they sought the easiest, most familiar materials to work with. I'm not saying that it wasn't better than the previous, and yes, if you are careful, the outcome may be positive, but the warping that is regularly seen with WBP has always been a concern to me, and something you don't see with marine ply. The other problem seen with WBP is that tiles can sometimes separate from the ply itself. There could be a number of reasons for this, perhaps PVA was used, which may be adequate on marine ply, but certainly not on WBP, which is why I mentioned an SBR primer.
But you're right, there is no silver bullet, you have have to go with what you feel and follow best practice.
All the best
____________________
paulc2012
http://www.oakenstone.co.uk

 

[Rich]

Wasnt having a pop, was just trying to make a point about different ply. I always try to use a backer board, as I really dont think any wood is an ideal substrate. This problem is made worse by builders (and some tilers) who, like you said above, got over confident with it. Iv put a lot of jobs right because the builder had used the wrong ply. I have a bit of a problem with people saying 'Its ok, its marine ply' when I walk onto a job, a lot of people think thats fine without checking that the ply is not protected with anything such as fire resistant ply that makes it very hard work to adhere to.

:8:

 

[DHTiling]

Just to add.... A lot of ply is imported and the resins in the ply leach and can cause tile adhesive not to bond to the ply.

This is one of the reasons i now avoid using ply as much as i can.. i would say that i know use hardi on 99% of my jobs..the only odd occasion is a builder has already plyed.

 

[paulc2012]

Alright, let go, you're twisting my arm.

But seriously, I wonder Dave whether it might be worth moving this part of the thread to another topic, because it's a fascinating discussion.

I suppose it all comes down to our own personal experience, our 'wish list' for current materials, how we see them developing, and perhaps as important a guiding factor as all these, our own perspective on sustainability, which is where I'll make myself popular, I can see....

I'm not sure whether the issue of the ideal board for fitting tile to is a closed book or not yet. In fact I am sure, because the ideal board, even in the short term, hasn't been created yet.

I've created a couple of new threads, one on the ideal board

http://www.tilersforums.com/tiling-forum/32766-ideal-board.html

and the other on sustainability in tiling

http://www.tilersforums.com/tiling-forum/32765-sustainability-tiling.html

I'll start the diatribe in 'ideal board' later. If any of you get there first, that would be great. Its an important issue and one that needs to be talked about.

All the best for now

paul
___________________
http://www.oakenstone.co.uk

 

[Rich]

Same goes Dave, Iv said a thousand times but I use a backer anytime I have a choice in the matter.