Bathroom floor advice please

[davemul]

Evening all

Our bathroom (that I am gutting) has floorboards, some sort of 6mm board nailed to them and some rank lino. There is movement in the floor, probably the old knackered floorboards (house is an OLD cottage)

Can I take the floorboards up completely and replace with 18mm plywood to establish a firm base. I will be inserting a wetroom tray directly to the joists and then tanking and tiling the floor.

to totally waterproof the floor, would 18mm ply, tanking then tiling do the job?

thanks

Dave

[Dave]

The use of a membrane would be my option Dave.. but the walls will need doing as well..

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[davemul]

Thanks Dave, PHG will be my first port of call.

So I am good to go with 18mm ply directly on to the joists. Then a membrane or some other form of waterproofing?

thanks

Dave

[Bri]

When you take the floor up check the condition of the joists firstly, if they are sound add some extra noggins for strength, then lay 25mm ply if you can afford the extra height. I'd also overboard the ply with a 6mm cement backer board to give a more suitable surface to tile to. Getting rid of the deflection is essential to ensure your floor will last years not months. Hope this helps. Bri

[Dave]

25mm is the better option but if the joists are able to support he weight and you noggin it out then 18mm will suffice.. 22mm tray onto joists .. so 18mm ply and 3mm membrane/addy will bring up the height to tray height.. Marmox shower stone is a great option from PHG..

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[davemul]

Thank you gents.

Just a thought, instead of using plywood on to the joists, is it feasable to use marmox cement/foam boards fixed directly on to the joints? Ive just used 40mm marmox in my conservatory and it worked well, but this was on to a concrete substrate

thanks

Dave

[Dave]

I wouldn't..

[davemul]

Sorry to sound like a broken record.....

So.. marmox showerstone in the corner of bathroom, direct to joists. Plywood around this and for the rest of the bathroom floor.

Some form of tile backer board to bring up the height to tray.

tanking tape over the join from tray to boards (and obviously corner and wall joins. Will probably board the walls with marmox too and paint on a tanking solution

thats all i need to do to waterproof before tiling?

[Dave]

Use ply on the floor, then Dural Ci to tank.. no backer boards.

[davemul]

That looks like good stuff! can I lay UFH on top of it?

and how would I waterproof the join from the shower stone tray to the matting?

I will leave you alone eventually mate!

[Dave]

LOL.. UFH under it.. Ply is quite good as an insulator.

No probs glad to help.