Breifly In the process of replacing my bathroom suite with new bath , toilet , tiles etc.

I have a shower over bath and it has been leaking quite badly. Hard to tell for how long but maybe years .

The floorboard under the drip is rotten , enough to stick a screwdriver a good 2cm in to it. Problem is its also half under 2 walls.

Approx 1/2 of the board is under and internal wall width ways and each end protrudes under other walls ( flat conversion )

If I set at with a chisel to remove as much of the rot as possible how do I replace it ,or do I just leave a gap?. Not a load bearing area , it will be under the new bath but really want to check the joists under the floorbaord are OK and not rotten too.

At the moment the bath ,tap feeds, waste pipes and some hardwood is all in the way so even getting a good look at the extent of the water damage is tricky .

Cant believe downstairs doesnt have a large damp spot on their bathroom ceiling but notings been said. WWYD.

Wait til the old bath is out and replace rotten board then. Meanwhile paint tray below leak( if you’re still using shower)

Must only be stud partition walls it’s under? If so the plaster would have sucked up water and be showing damp. Find the extent of rot and then cut it out. Or, if it’s hidden under the bath, just sort the leak and treat the rot? As you say, floorboards aren’t structural. You can get some paint on rot stop stuff that does a pretty good job – meant for window frames.

Remove bath and remove all damaged area and re plaster and re floor
Depending when your place was refurbished there maybe fire retardant material between the flat down
stairs between your flooring joists that maybe absorbing the leaking water.
You will find this when you replace the flooring.

Re floor, you only have to replace the floor board to the nearest joist, so try and find where they are. If someone has put a partition wall in to make the bathroom, then the floor boards will run under the wall. If you’re lucky the wall is above a joist if not you may have to cut the floor board inside the next room and then slide the replacement 6″ under the partition wall….

My house is the same, this is the back bedroom floor and there is a partition wall to the bathroom (where pipe run to under the wall):

[url=https://flic.kr/p/orRKgK]Repairing rotton joists[/url] by brf, on Flickr

I cut the floor boards mid way through the last joist and replaced them in the rear bedroom. It’s not very clear in this photo, I think I initially cut them at the side of the joist and then trimmed them back mid way using one of these:

footflaps picture looks very much like my flat. Every DIY project becomes a battle as I uncover things like this everywhere. The rotton board projects under a grey block wall, like celcon but more robust . Then under the adjoining kitchen .

I want to get a professional plumber in to do the refit whilst Im away and cant live without a shower for the time it would take me to remove bath , fix flooring , refit new bath and seal etc.

Did you find half a tonne of rubble and rubbish under the floor? The builders must have just swept all the left over materials between the joists and then laid the floor. Lazy twunts!

Is the board rotten all the way to the wall? Had similar recently, on one side of the bathroom the boards were soft but there was a double beam along the wall so it was possible to cut along there and replace. On the other side the board wasn’t soft, but went under the wall into the next room. I just cut along the wall and put in a noggin at 90deg to the beams, to support the new chipboard.