Overboarding options...

[hoglet]

Hi All!

I'm going to take delivery soon of a steel bath, and need to make a decision soon on overboarding.

I'm going for ceramic tiles and this is my first tiling attempt.

Joist centres are 400mm with joist width 50mm and joist depth 225mm. Bathroom floor area (excl. bath) is tiny - just 2M X 1.15M. Existing floor is 18mm T&G. I say T&G, but some boards have been replaced with ply and so therefore the floor is also partly composed of square edge 'boards'.

I've dismissed removing all the boards and fitting nogged 25mm WBP. Reason is due to the stud walls making it difficult to remove some of the existing boards at the floor perimeter.

So, I'm torn between hardie and ply. I've done a lot of searching on this excellent site and it appears that the choice of substrate largely depends on the deflection/rigidity of the existing floor and the tiler's preference.

The existing ply in the bathroom was installed 18 months ago by a CORGI/GSR installer after running pipework under the bathroom floor as part of a new combi install. The ply now flexes like billy-o - it really flexes a lot! ! The installer did not nog at the ply board edges. I'll post a pic if necessary.

I'll replace the ply with square edge softwood (e.g. pine) boards, screw down existing boards and make good. Then I'll overboard. I'd like a sheet material that has the dimensional stability of cement backerboard but the thickness/rigidity of 12 (18?) mm ply. I don't think I have confidence in a 6mm backer board...

The thickness of this backerboard looks ideal:
http://http://www.cgcinc.com/pdf/dat...NG_Data_EN.pdf

[ame]http://http://www.youtube.com/watch?v=3z6rPLxtKS8[/ame] @3:01

Fitting 12mm ply and 6mm hardie on top seems an unusual approach, but I'm thinking about that.

I realise there will be a height differential with the landing, but hey, if there's gonna be a step - might as well make it 18mm rather than 12mm (+ tile/adhesive).

Decisions decisions...

Cheers for any advice!

Hoglet

[whitebeam]

6mm hardie is good stuff, the guy on the video was using 12.5mm on the floors, never used for that.

Just secure any loose boards and fix well

[hoglet]

Thanks a lot for your help whitebeam. I'm sure it'll work out!

Hoglet.

[hoglet]

I'm going with the 18mm WBP ply. I want rigidity as this is my first job. If I had more confidence in the boards, I'd most likely use 6mm Hardie.

I'd rather live with the height difference and have the floor solid.

Should I glue and screw or just screw?
Any particular adhesive?
Can someone post a link to a threshold bar that would accommodate the height difference? Will I need some custom joinery?

I'll also sink some of the screws through the joists.

Thanks a lot,

Hoglet.

[doug boardley]

just screw it down at 150mm centres, try and get as many screws into the joists as possible, but beware of sub floor services, ie water, electrics etc

[wetdec]

If the room is stripped then take up the floor the plumber put down. If there is a problem then thats where you start covering it up isnt the answer.

Rip out existing put subframe right and relay with 22/25 mm ply " do it right once "

[hoglet]

just screw it down at 150mm centres, try and get as many screws into the joists as possible, but beware of sub floor services, ie water, electrics etc

I'll leave out the adhesive and will defo sink some screws into the joists. Fortunately I know exactly where the services are as they are under the ply areas that the plumber replaced the old T&G with.

Best,

Hoglet.

[hoglet]

If the room is stripped then take up the floor the plumber put down. If there is a problem then thats where you start covering it up isnt the answer.

Rip out existing put subframe right and relay with 22/25 mm ply " do it right once "

I quite fancied taking out the entire floor and replacing with 22/25 mm ply nogged at the board joins. It's more trouble than it's worth as the stud walls are in the way at the entrance to the bathroom.

I've often read on here and elsewhere about taking up the existing floor, but (I'm guessing) that it may be impractical in a lot of cases because some T&G may pass under walls and can't be taken up. Unless there's a workaround?

If there is a problem then thats where you start covering it up isnt the answer.

Huh?

Best,

Hoglet.

[hoglet]

Hello All,

Here's the (feeble) floor size:

I'm aiming to use a single sheet of WBP ply and stitch drill the hole for the WC waste - I don't think a coping saw will be big enough for the size of the ply sheet. I'd be interested to know what method the trade uses to cut the hole for the WC waste. I don't own a jigsaw!

Much obliged everyone,

Hoglet.