Old suspended floor joists

[JP_]

I've posted a fair bit about my suspended floors. Currently doing the bathroom.
I cut out the rotten wood, came back a metre and while the cut was clean, no rot inside the wood. the underside where it sits on a sleeper wall had signs of rot.

Is this normal and OK? I've sprayed everything with Everbuild Triple Action. The space will have more ventilation and less moisture getting in than it had before. 85 years old, so not bad really!

Plumber arrives tomorrow to start drainage and first fix, and we hope to get the shower tray in too as it will sit direct on the joists. So if we need to replace all, then probably best I hold fire on the shower tray....

I think it's OK ...

but then getting a few new joists is pretty cheap ...
https://www.gards.co.uk/product-range/regularised-treated-carcassing-grade

 

[Lower]

A little bit of wet rot in an unventilated area is normal. Cut it back past as you've done, replace the wood you've cut out with sistered joists, improve the ventilation and it should be good for another 85 years.

Are you creating a flat panel to sit the shower tray on or will it only be sat on the joists? Will it adequately supported like this?

 

[JP_]

Plumber said he'll put on the joists, bed it down with some mortar. Might need to put some extra support in. Sounds like a good idea to me .. my thinking, other than less floorboards to buy, is that if in future there is a leak it is more likely to drop down onto the concrete and evaporate away, than sit on the floorboards and creep to the joists. Also makes it easier to fit the drainage and test before putting the floor down. I'm letting my plumber take care of all this though.

 

[JP_]

is 18mm of this plywood good for bathroom floor?
https://www.gards.co.uk/product-range/8-x-4-ext-hardwood-faced-plywood

 

[Lower]

Plumber said he'll put on the joists, bed it down with some mortar. Might need to put some extra support in. Sounds like a good idea to me .. my thinking, other than less floorboards to buy, is that if in future there is a leak it is more likely to drop down onto the concrete and evaporate away, than sit on the floorboards and creep to the joists. Also makes it easier to fit the drainage and test before putting the floor down. I'm letting my plumber take care of all this though.

Depends on the type of shower tray you're using. To rest on the joists it would have to be structurally strong enough to bridge the gap between the joists without flexing or cracking. Most aren't.

It would easy enough to use noggins between the joists and insert 18mm ply on top to create a platform for the shower tray flush with the top of the joists.

What flooring are you putting down in the bathroom?

 

[JP_]

Shower tray will be a stone resin one, plumber did mention noggins.
Probably just vinyl sheet flooring for now - something cheap.

 

[Lower]

I'd choose WBP plywood for a bathroom.

 

[JP_]

thanks, will seek those out.

 

[JP_]

I misunderstood what his plan was. He's going to put noggins in below top of joist, put ply on these, then mortar the whole area for the tray so it's level and solid. Will be resin tray.

 

[Lower]

That’s the right way to do it