Stick or not hardiebacker board.

[Jon329]

Hello, finally got around to getting my floor down, I've used 6mm hardiebacker on top of a new 18mm plywood sub floor.

Now I know the idea behind sticking the boards down with adhesive is to eliminate any unlevel/air gaps under the boards, however this floor is brand new and the bathrooms so small theres only one join on the plywood floor.

I don't really want to use the adhesive as I think it will raise the floor height above the shower former to a point where I'd have a hard time lifting the former by such a small amount. At the moment the formers about 1-2mm lower which I think is probably ideal

I know some of you tradesman only use screws, so what's your thoughts?

Cheers!

 

[J Sid]

adhesive and screw on wood every time

hoped you sealed back and edges of ply

 

[Waluigi]

6mm notched trowel on the floor. Gluing is essential, so is screwing. Then tape and fill the joints.

 

[Jon329]

Does the ply need sealing? It's going to be tanked as it's a wetroom and it's not marine ply anyway? The plywood has only been cut on the wall edges, so I guess it would only be needed to be sealed on cut sides?

The general opinion I got from people was if you have water getting through the tanking it doesnt really matter what you treat the wood with, it will start to rot if it's always damp anyway

Cheers

 

[J Sid]

it should be seal back and edge to stop moisture getting in even if you tank, no found a build who has ever done this. Surface sealing depends on what the adhesive recommendation is for your chosen adhesive.

 

[Jon329]

I can still lift the boards, so I guess just coat the back and sides, leave to dry and screw back down.

Does anyone know if your ment to use the hardie scrim tape and then put tanking tape over that too? Or can I just put the tanking tape on and forget the scrim tape.

Cheers

 

[Waluigi]

Is the proposed wet room on a ground floor with suspended timber joists?

 

[Flintstone]

I don't think 18mm ply is sufficient for direct to joist. What's happening with the walls ?
XPS foam board throughout walls and floor would be the way to go with this room

 

[Jon329]

The walls will have the wall paper and paint stripped and then I will be applying a liquid tanking to the plaster, which will have tiles.
The walls are all solid, no plasterboard in this room

Yes ground floor and is suspended timber construction.
I have put plenty of noggings in so the 18mm should be fine.