'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

 

[plastic_peanut]

Either remove the old floorboards and put thicker boards down or use a thicker board over the top as you suggested. Using a thinner board isn’t worthwhile as you will undoubtedly have the grout cracking and regret it quite quickly. False economy as i learned the hard way

 

[robodelfy]

Either remove the old floorboards and put thicker boards down or use a thicker board over the top as you suggested. Using a thinner board isn’t worthwhile as you will undoubtedly have the grout cracking and regret it quite quickly. False economy as i learned the hard way

Thanks, why thicker floor boards, these ones are thick just a bit all over the place, bowing etc.

So what would you say is thick enough ply to put over the top before using the No More Ply? Keeping in mind I want to add as little height to the floor as possible

 

[catlad]

I did my bathroom in 6mm ply over old floor boards glue down and plenty of 25mm screws & flexable tile adhesive and its still sound 10yrs later

 

[plastic_peanut]

I did my bathroom in 6mm ply over old floor boards glue down and plenty of 25mm screws & flexable tile adhesive and its still sound 10yrs later

Always helps if you have a flat surface to start with, if not it can become a headache

 

[robodelfy]

I did my bathroom in 6mm ply over old floor boards glue down and plenty of 25mm screws & flexable tile adhesive and its still sound 10yrs later

Good to know. 6mm ply is very i, and I don't think would be sufficient for my floor, but the No More Ply is more rigid

What glue did you use?

 

[catlad]

Geocel Quickgrip supergrab 3 or 4 tube. The floor doesn't need to be super flat it just needs to be stable.

 

[robodelfy]

Geocel Quickgrip supergrab 3 or 4 tube. The floor doesn't need to be super flat it just needs to be stable.

Yeah the only reason I worried about it not being flat all over is the glue not grabbing at all.

I'll look up that glue. I have a tube of sikaflex which may do much the same job. It's flexible but also incredibly strong

 

[catlad]

Sika is good stuff

 

[JaimieH]

Mega Adhesive is polyurethane based and will foam up to fill voids up to a certain size. Dampen the backs of the NMP with water and the floorboards before laying to help the curing process. If your floorboards are really uneven or badly cupped you can bed the NMP onto rapid set flexible tile adhesive. Still use the Mega Adhesive along the joints to bond them together. Once set screw the boards down every 300mm using NMP 25mm screws. Remember to lay the boards in the opposite direction to the floorboards and stagger any joints. NMP is the better surface to tile on.

 

[robodelfy]

Mega Adhesive is polyurethane based and will foam up to fill voids up to a certain size. Dampen the backs of the NMP with water and the floorboards before laying to help the curing process. If your floorboards are really uneven or badly cupped you can bed the NMP onto rapid set flexible tile adhesive. Still use the Mega Adhesive along the joints to bond them together. Once set screw the boards down every 300mm using NMP 25mm screws. Remember to lay the boards in the opposite direction to the floorboards and stagger any joints. NMP is the better surface to tile on.

Thanks that's great advice. It's hard to say if my floor is bad enough to need tile adhesive or just the mega strength adhesive. It's probably borderline!

The area I need to tile is 2.4 x 1.2m so I need 4x nmp boards, but obviously can't stagger them, is that ok?

And finally, I have two copper pipes for the towel rad, would you drill holes in the NMP for these, or cut out a triangle from the edge of the sheet?

Thanks again

 

[JaimieH]

If the floor isn't too bad the mega adhesive will be fine. I usually use 1 tube per 3 sheets so you'll need 2 tubes. You can stagger the joints by cutting the 3rd sheet in half and starting the 2nd row with half a sheet. Staggering increases the overall strength of the floor but remember to use the glue along all joints as well as underneath. It will foam up above the joint so wait 20-30mins for it to cure and then run a sharp scraper or chisel along it to remove the excess. I'd measure carefully and drill holes as opposed to cutting triangles. A carbide holesaw will work best. I use these
https://www.toolstation.com/search?q=Carbide grit holesaw

 

[robodelfy]

If the floor isn't too bad the mega adhesive will be fine. I usually use 1 tube per 3 sheets so you'll need 2 tubes. You can stagger the joints by cutting the 3rd sheet in half and starting the 2nd row with half a sheet. Staggering increases the overall strength of the floor but remember to use the glue along all joints as well as underneath. It will foam up above the joint so wait 20-30mins for it to cure and then run a sharp scraper or chisel along it to remove the excess. I'd measure carefully and drill holes as opposed to cutting triangles. A carbide holesaw will work best. I use these
https://www.toolstation.com/search?q=Carbide grit holesaw

Thanks, you can see the floor in the first photo, it's not the worst, bur there are some lumps and bumps, so I might try and plane down the high spots

But on such a small floor, and such small sheets doesn't cutting one in half just to stagger them negate the added strength? Would it not be stronger to just lay 4 sheets next to each other? It will have less joints then?

Ok I'll get a drill bit that can cut holes

 

[JaimieH]

You have less joints but one of them is a long one running parallel to your subfloor joints. If you're unlucky it could sit bang on top of one of the floorboard joints which creates one long potential weak point stretching through all layers. Probably wouldn't be an issue with laminate, vinyl etc but with tiles you're asking for trouble.

 

[robodelfy]

You have less joints but one of them is a long one running parallel to your subfloor joints. If you're unlucky it could sit bang on top of one of the floorboard joints which creates one long potential weak point stretching through all layers. Probably wouldn't be an issue with laminate, vinyl etc but with tiles you're asking for trouble.

So if it doesnt sit right on top of a floorboard joint, and sits across the middle of a board, would you still cut one piece and stagger it? I can't help but think it creates a weaker floor overall to have many more joints, but I am a novice