Best subfloor for tiles?

[RF Lighting]

Hello all.

I'm working on a little project at the moment. It is a small toilet block in a scout & guide hut.

There has been a leak under one of the basins, which has gone un noticed for some time now.

As a result, many of the floorboards, and possibly a couple of joists need replacing.

The whole area will have a tiled floor due to kids spilling water (and the rest) on the floor, as it is the easiest to clean and the hardest wearing surface.

Now here is my question.

What is the best subfloor to install direct onto the joists? They are 2" x 6" timber joists on 16" centres.

I was wondering if something like 18mm ply direct to the joists would do it, but I can see problems with movement on the joints between sheets which would be a problem.

So my next thought was flooring grade chipboard. Its nice and cheap and easy to fix, and then over board this with some thin ply. Something like 6mm?

I would fix the FGC with my paslode gun and either ring shank or glue tipped nails.

What would be best for sticking down the ply?

I thought laminating it to the sub floor with PVA and then tack or screw it?

Any thoughts and suggestions would be more than welcome.

Thankyou

 

[lancenotalot]

I use 25mm wbp ply when replacing a floor and fit noggins on the joints,some will advise that 25mm is overkill and advise that 18mm will suffice.

 

[Richard C]

Not just your ordinary bathroom! With lots of kids likely to be jumping up & down on it, I would say you’ll need at least 25mm ply & even 2 x 18mm ply, cross laid. I wouldn’t normally even consider chipboard as a base for tiling but, to keep costs down, you could use 18mm flooring grade as a base & overboard with WBP but 6mm is way too thin even for a conventional bathroom; I would say at least 18mm & possibly 25mm.

 

[RF Lighting]

I have previously had some cheap ply.

I think it was construction or shuttering grade. It was badly finished, but cheap as chips.

What about this as the first layer straight onto the joists, and then WBP over the top with the joints staggered?

Both boards would be 18mm thick

Is WBP the same as marine grade ply?

I have seen somewhere about screwing the boards together at 200mm centres. Is this the right spacing?

Is it worth glueing the sheets together, or will the screws suffice?

 

[gcol]

RF, just do this:

I use 25mm wbp ply when replacing a floor and fit noggins on the joints...

Screw into the joists and noggins every 250-300mm (200mm is for overboarding with 12mm ply and is a bit much for 25mm). Screws 5 x 60mm countersunk.
For adhesive, use Bal rapidset flexible.

WBP is not as high a grade as marine, but it's fine for what you want.
Consider sealing the edges and underside of the sheets - fence paint is a cheap way of doing this. Do not seal the face to be tiled.

 

[Richard C]

I have previously had some cheap ply. I think it was construction or shuttering grade. It was badly finished, but cheap as chips. What about this as the first layer straight onto the joists, and then WBP over the top with the joints staggered? Both boards would be 18mm thick

Should be fine; if it’s shuttering grade it might even be WBP.

Is WBP the same as marine grade ply?

Marine play is made with waterproof glue in much the same way as WBP but outer facings on marine ply are much higher quality with a superior finish, basically it’s used for boats & is why it’s so much more expensive; complete overkill for a bathroom floor!

I have seen somewhere about screwing the boards together at 200mm centres. Is this the right spacing?

I’d go with screws at 150mm centres rather than nails & make sure they go into the joists on both boards; don’ rely on just screwing the top boards to the bottom ones.

Is it worth glueing the sheets together, or will the screws suffice?

Laminating the 2 boards into one will always be stronger but if you screw both into the joists they should be fine; position the joins over a joist or intermediate noggins.

 

[RF Lighting]

RF, just do this:

I use 25mm wbp ply when replacing a floor and fit noggins on the joints...

I'm going to need my weetabix to lift that stuff onto the roof rack


Thanks for the advice chaps. You can each have a pass for one free question in Electrics UK. Just ask for RF


I'll try and remember to take a few photos as I go along (or is it just us lot in the electricians forum who love photos?)

There are some tiles there at the moment stuck straight to the damp rotten floorboards

 

[gcol]

I'll try and remember to take a few photos as I go along (or is it just us lot in the electricians forum who love photos?)

No, feel free - we love piccies too.

 

[Richard C]

Thanks for the advice chaps. You can each have a pass for one free question in Electrics UK. Just ask for RF

Couldn’t sign off a few bit & pieces for me as well could you

 

[RF Lighting]

As much as I'd love to, I'm not even allowed to sign my own work off.

 

[RF Lighting]

I know it's been a while, But I did promise pics.

Here is the damp from a leaking waste pipe (it has been replaced in that pic), which lifted the tiles off the floorboards.

Cracked already

More missing tiles

Hmmm

Bit of silicone will get that

Interesting....

I'm hopefully going to be replacing this lot over the summer holidays while the building is empty.

I'll take some during and after pics for you to pick fault with

 

[jefoss]

you got your shoes on the wrong feet mate

 

[lancenotalot]

I'm sure you could patch that up with a bit of grout and some silicone you got your work cut out RF.

 

[gcol]

you got your shoes on the wrong feet mate

Brilliant. I've nearly got tears laughin'.

 

[RF Lighting]

They really are on the correct feet.