'No More Ply' on old floorboards...

[robodelfy]

Hi, I bought 6mm No More Ply for my bathroom floor before I tile.

As you can see the floorboards are not perfect, and there is a piece of ply patching in one section. It all feels quite solid to me, but not perfectly flat everywhere as the boards are old. My worry is that when I put down the No More Ply that the Mega Strength Adhesive won't touch everywhere due to bowed boards etc. But I also read that the glue expands?

Would it be a better to lay 12 to 18mm ply down over the current floor before even using the No More Ply? I'd rather not add that height to the floor, but I want to do it properly.

If I was to do this, what would you use to attach the ply to the current floor? Just screws, or Sikaflex? It would be nice in the future if it wasn't impossible to get up if I want to change the floor.

Any advice would be great
Thanks

 

[Tile life]

If it where my floor I would go with the 12 mm ply on top of the floor boards. A good sticky tile adhesive mix ( with a bunch of SBR) troweled onto the floorboards and then screw it millions of times. Once it’s all guaranteed solid then apply surface treatments to hold tiles better. Having said this I have never used Nomore ply so don’t k ow what it’s capable of.

 

[Andy Allen]

can't say I'm a fan of nmp, brittle crap imo, hardie board is much better, but as you already have it I would ditch there adhesive and stick it down with tile adhesive ( not ready mixed) use a 10mm trowel and 25mm screws this should take up the bow in the floor boards.

 

[robodelfy]

If it where my floor I would go with the 12 mm ply on top of the floor boards. A good sticky tile adhesive mix ( with a bunch of SBR) troweled onto the floorboards and then screw it millions of times. Once it’s all guaranteed solid then apply surface treatments to hold tiles better. Having said this I have never used Nomore ply so don’t k ow what it’s capable of.

So are you saying you'd use 12mm ply but not the No More Ply on top of that? I was thinking of some ply, then the No More Ply.

So you can just use tile adhesive to stick the ply to the floorboards? I was also wondering about something like Sika Flex instead? And screws of course

And what are surface treatments to hold tiles better

Thanks
[automerge]1593191993[/automerge]

can't say I'm a fan of nmp, brittle crap imo, hardie board is much better, but as you already have it I would ditch there adhesive and stick it down with tile adhesive ( not ready mixed) use a 10mm trowel and 25mm screws this should take up the bow in the floor boards.

I'd read mixed opinions on NMP vs Hardie, but yeah it was all that was available locally. They say to just use a few beads of their Mega Strength Adhesive, and apparentlyits very strong and expands. Would it work to use a bit of both, some tile adhesive in the middle and the bead of their glue around the edges?

And is that standard practise to stick Ply or NMP down with tile adhesive? This is my first time tiling

Any reason why I shouldn't put some ply down before the NMP, maybe even 9mm or 12mm would help even things out?

 

[Andy Allen]

just tiled this floor, onto floorboards that were worse than yours using nmp... as it's all I could get during lockdown , and using the exact method I mention in my last post. the tiles were stuck down using bal single part fast flex, and grouted with bal wide joint grout with GT1 admix.

 

[Steve6690]

Putting down ply and then NMP on top is unnecessary and is introducing an extra point of potential failure. The adhesive under the NMP is to fill in the void beneath and provide a full, solid bed beneath it. You might find it easier to stick the NMP down so it's a nice flat surface to tile onto, and then fit the screws once the adhesive is set. That's what I'd do, but others may think differently.

 

[robodelfy]

Putting down ply and then NMP on top is unnecessary and is introducing an extra point of potential failure. The adhesive under the NMP is to fill in the void beneath and provide a full, solid bed beneath it. You might find it easier to stick the NMP down so it's a nice flat surface to tile onto, and then fit the screws once the adhesive is set. That's what I'd do, but others may think differently.

Thanks, yeah I did consider adding ply may not be helpful, also may introduce more potential squeaks or movement.

My concern with my floorboard is not the overall perfect level, its the dips and bows in the boards, I just wonder how well the the adhesive will fill these gaps. Butpeople have said the NMP adhesive expands. Others have said stick the ply down with tile adhesive if I want to fill the gaps. I may be worrying about nothing, but I just know once its stuck its a nightmare to get up!

 

[Andy Allen]

definitely DON'T put the screws in when the adhesive has set, it needs to be screwed down while the adhesive is still wet...

 

[robodelfy]

definitely DON'T put the screws in when the adhesive has set, it needs to be screwed down while the adhesive is still wet...

Thanks yeah that makes sense. Someone told me to stagger the boards even though my room is tiny, its exactly four 1.2 x 0.6 NMP boards. He said cut the last board in half so you can stagger them. I understand the reason why on a bigger floor, but it seems like I'd be creating more unnecessary joints then. What do you think?

 

[Andy Allen]

yes stagger them, it limits the stress points on the joins.