Floor advice please - ply or marine?

[Deleted member 51575]

Hi, I have newly built shell of an extension and we are just starting first fix plumbing. The floor joists are in place but my builder and plumber seem to have a difference of opinion on the flooring for the bathroom.

The builder says the green coated 18mm ply is sufficient, whilst the plumber insists on marine ply. The joists are all brand new and have noggins. We anticipate tiling the floors. (50x250mm timber joists @ 400mm
centers).

Would just 18mm ply be ok or am I better to spend the extra for the marine ply. Plumber suggests the maring ply should be glued and then screwed every 100mm.

Is just one layer of 18mm sufficient on top of floor joists?

thanks in anticipation..

 

[Waluigi]

Two options- Ply wood and overboard with a tile backer board.

Or, a thick cement board directly on to the joists.

A lot depends on what exactly you’re fitting on the bathroom floor in terms of tile type and whether there’s UFH (wet or dry) or not.

On a Personal level I’ve never used the thick cement board. It’s an idea that gets suggested a lot but very rarely done. For a reason I don’t yet know.

 

[Deleted member 51575]

One bathroom will have electric UFH, and the other one wont have any UFH. Does that change your suggestions?

 

[hmtiling]

Two options- Ply wood and overboard with a tile backer board.

Or, a thick cement board directly on to the joists.

A lot depends on what exactly you’re fitting on the bathroom floor in terms of tile type and whether there’s UFH (wet or dry) or not.

On a Personal level I’ve never used the thick cement board. It’s an idea that gets suggested a lot but very rarely done. For a reason I don’t yet know.

Price and availability

 

[Middlesex Tiles]

Any chance anyone can give me an indication of how much they have to pay for the 22mm cement boards and also how much they would be willing to pay if the current price is too expensive.

 

[Waluigi]

One bathroom will have electric UFH, and the other one wont have any UFH. Does that change your suggestions?

Yes it does.

One overboard with a thin cement board, the other with UFH is overboard with an insulation board. Both, glued screwed, taped and filled.

If you went for the thick cement board on to the joists then the UFH room might still need overboarding if you want the most efficiency as the cement board acts as a heat sink somewhat.

That said, I have laid UFH on cement boards before and they actually work reasonably well.

 

[hmtiling]

Any chance anyone can give me an indication of how much they have to pay for the 22mm cement boards and also how much they would be willing to pay if the current price is too expensive.

About £35 Inc for 2400x500 and that's too much

 

[Waluigi]

I think that’s reasonable

 

[hmtiling]

I think that’s reasonable

Even if you think that why would you say that to a supplier? Jeez

 

[Waluigi]

Tuck it away Lad.

 

[hmtiling]

Tuck it away Lad.

?

 

[Waluigi]

It has a double meaning. Tuck away the hard on you have and also the post containing the price in the open forum

 

[hmtiling]

It has a double meaning. Tuck away the hard on you have and also the post containing the price in the open forum

That's the second time I can recall you stating other members have a hard on. A pattern is emerging

 

[Middlesex Tiles]

About £35 Inc for 2400x500 and that's too much

It looks like the product is commercially unviable - it wouldn't be worth stocking it to sell at that price, and that's too high for you guys!!

 

[Unused Account 1]

Use a decoupling matt for ufh,straight onto ply ,just an idea