Help!: Overboarding a floor

[J.R Tiling]

Hi Guys

Have a small (5m2 approx)bathroom floor to do next week and am going to have to overboard the existing floorboards just want to make sure im doing it the correct way.

Is this the right way to go about it ?

• Lay 12mm ply ( do i need a gap between sheets/walls ?)
• Screw down ply
• Prime
• lay tiles using a flexable adhesive (bal Rapidset)
• Grout (flexable)

Many Thanks John

[Thespanishtiler]

personally i would use hardibacker if the sub floor is sound, ie no deflection of joists,

[grumpygrouter]

Hi Guys

Have a small (5m2 approx)bathroom floor to do next week and am going to have to overboard the existing floorboards just want to make sure im doing it the correct way.

Is this the right way to go about it ?

• Lay 12mm ply ( do i need a gap between sheets/walls ?)
• Screw down ply
• Prime
• lay tiles using a flexable adhesive (bal Rapidset)
• Grout (flexable)

Many Thanks John

BAL Do not recommend anything less than Fastflex if you use less than 15mm ply. Also with bal products you do not prime the face of the ply, you should seal the underside and edges with SBR though.

[groucho]

ive never used ply to overboard. always no more ply or hardi backer boards. so much easier to install no floor height issues and apparantly the same strength as 18 mm ply ( no more ply ) NMP is £10 a sheet and covers 0.72 sqm. Glue and screw. Glue is £ 10 a tube bloody strong. You could hang your self from the ceiling with that stuff

[pt44]

Maybe I do the overkill method but here goes

Firstly, I screw down all of the existing boards, so they are well clamped to the joists

Next, 18mm WBP, this needs to be primed on the underside and the edges, not the top tiling surface. Unless the surface gets very dusty before tiling.

Screw the 18mm ply down, preferably through to the joists. Leave 1mm gap between the boards and about 2-5mm at the edges of the room.

Only downside, it raises the floor level. But it sure doesn't move.

Paul

Not thought of using hardibacker on floors as an alternative. I don't like it for building usually as its crap when you screw into it near edges etc. Breaks apart too easily. However, for floors it might be worth investigating. Not sure how it bears up strength/flex wise though. 18mm ply simply doesn't flex - over joist distances. When I started doing floors over wood, I wouldn't have considered 12mm ply thick enough, but perhaps I am wrong.

[smurf21]

overboard with no more ply ,mega adhesive and screw 6mm = 18mm ply reduces step in doorways easier than fitting ply plus its waterproof then you can use single part flexi, dampen boards before spreading addy

[J.R Tiling]

Do you know were i can pick up the "no more ply" dont think ive seen any of it about

[smurf21]

No more ply, water resistant tile backer board
click link

[JPT]

Hi. I woulde secure the existing floor and the use hardi backer. I've used flexible adhesive to secure this in the past. rather tha screwing. the 6mm backerboard is fine and Topps have it at about £8 a sheet if your trade

[grumpygrouter]

ive never used ply to overboard. always no more ply or hardi backer boards. so much easier to install no floor height issues and apparantly the same strength as 18 mm ply ( no more ply ) NMP is £10 a sheet and covers 0.72 sqm. Glue and screw. Glue is £ 10 a tube bloody strong. You could hang your self from the ceiling with that stuff

This claim by the improters of NMP have never substantiated their claim, even though we have asked on these forums for them to clarify their findings. We have, as yet seen no documentary evidence supporting the claim that NMP actually provides the same strength to a bouncy floors as 18mm ply.

As far as I am aware ALL other cement backerboard manufacturers claim should be adequately braced to avoid movement before the board is used. Can't see why NMP would be any different in this respect.

[pt44]

As usual I have so many questions.

So, from what I can tell "no more ply" is a cement based board. And I cannot find anything saying that it is not in fact extremely similar to Hardibacker and Aquapanel boards. Sounds like the same stuff. Or does it have some other magic ingredient in it?

As far as my experience and common sense goes, there is no way that a 6mm sheet of anything cannot be flexible over a board size. Especially when compared to 18mm ply. However, I can believe (I think) that it is rigid enough when glued to a floor to make that floor rigid enough to tile on. This is of course so long as the original floor is fairly rigid. Floorboards being screwed down into joists etc. Perhaps if the joists themselves are bouncy, then they need extra noggins etc.

However, perhaps my usual belt and braces method, though effective, is perhaps total overkill for most situations. Perhaps I can get away with "no more ply" in future. Laminates are extremely strong, and glueing this board to an existing floor is creating a laminate. The polyurethane glue is damn strong stuff, I've used similar before to glue a Wedi shower tray together.

Unfortunately, bounce in floors is a subjective discussion. So its impossible on a forum to judge how much flex a floor can or cannot have before tiling it. I would be very interested to see how many people are using "no more ply" on the forum - with success or without.

Paul
PT HomeImprovement

[macten]

I had my doubts too but was forced to use it on a kitchen floor that had a sliding door as a ply overlay alone would have been higher than the framework of the door. I was so impressed with the NMP I often use it and have never had a problem, but then I wouldn't just screw and glue it down on a 'bouncy' floor.

As has been said already, I don't believe a 6mm cement board can provide the same strength of 18mm ply, but if the sub floor is made strong and NMP used correctly then it really becomes a very solid floor indeed and is a much better substrate to tile to compared with ply which is moisture and temperature sensitive.

BS state 10mm cement board as min for overlay.

[Uheat]

Hi Guys,

Why not try Thermopanel. This is a Thermal construction Tile backer board.
Elektra Thermopanel Tile Backer Boards from The Underfloor Heating Shop we have a great deal on it at the moment of £7.48 Inc Vat.