Finding the source of this mould/damp patch (pics)

[united4ever]

Hi, we have this mould patch (I am fairly sure that's what it is) and damp wall in our hall which is directly below the bath.

Outside there is this pipe, which is on the external side of the damp wall. I have never noticed it overflowing/leaking but i suppose it could be.
The corner of the bath is siliconed in in the corner. I guess there is possibly a leaking pipe underneath somewhere.

One other thing, we had cavity wall insulation put in a couple of years ago (soon after moving in) and I have heard that this can cause damp problems but the only part of the house with this problem is this corner and it's not heavily exposed to the weather.

I know this needs fixing but don't know where to start, I don't really want to pay a plumber to come out and rip the bath out if it may be something else. On balance a leaking pipe under the bath seems most likely. What do you think it is and What would you do? Who would you contact? By the way, I am in South Manchester if anyone knows someone who may be good

I noticed it before but it seems to have got a lot worse over the last few weeks/months.

Thanks in advance for your help.

My first thought would be an issue with the drainage pipes. Fill the bath and then go outside and carefully watch it drain; does it splash out of the hopper and onto the wall as it drains away? Has the hopper / drainpipe slipped down the wall from where it should be, or away from the outlet? Rule that out before you start ripping out the bath!

Almost certainly the drainage outside.

This looks more of a small leak. Pull the bath side panel off and check under your bath. Check if the floor boards are damp, if not, you might have to check your pipework underneath. If you're lucky, it could just be your waste pipe or overflow, or even just a poor seal around your bath.

I would check under the bath to rule that out first. We had a problem with the shower over the taps not forming a tight enough seal.

Our wall looked like that when one of our pipe connectors leaked.

Could be possible that you've two leaks?

A dehumidifier will definitely help dry it all out. It took about 4 days of having it running constantly to dry mine out.

Check the guttering above isn't leaking and also see if you can see there aren't any roof tiles or flashing out of place inside that corner area. The external wall looks dry and the pointing looks okay so I think it's probably an issue from the bathroom. It could be that the seal round the bath has gone rather than a leaking pipe or waste - take the bath panel off and have a look.

Thanks, unfortunately the side of the bath is tiled in so no side panel to simply take off. I could easily reseal around the bath and fix the damp patch and see if it comes back and then if it does then look at breaking a couple of tiles to look under the bath.

Sorry - i think you need a plumber. Sounds like something has been leaking for sometime and it needs fixing before it gets worse. Some times things just need to ge fixed!

looking at the pics, I think the centre of the wet patch is more likely under the bathplug than coming down the side wall.

If the bath panel has been tiled in, you will have to break it out.

this will be the time to resolve that any future bath panels or boxing-in are done using brass screws that can easily be removed for servicing.

Sorry but, one way or another, you will have to remove the bath panel. If you carry on leaving it, it will only get worse.

Thanks, yeah. How do you go about removing bath tiles, I'll just break the minimum required so I can see what's going on with a torch. Cheers.

You can use a wallpaper scraper and a hammer to tap it gently behind the tiles. Less chance of the tile splitting.

quite likely there will be screws holding the panel in place in the four corners, so start with them.

You might be able to deal with this without breaking through the side panel of the bath: we dealt with a similar problem by removing a small square from the ceiling of the room below. It gave us easy access and when the leak was fixed my husband put the piece of ceiling back again, filled around the cut edges, spent a LOT of time sanding it all smooth and painting it, and now you wouldn't even know we'd had it done.