fixing damp - cause unknown

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I'm not sure how to go about getting a spreading damp section of one of the internal walls of my house fixed. The house is a late victorian/edwardian semi, and we have a downstairs bathroom at the back of the house in an extension (added a long time before we moved in). The wall is the internal wall between the bathroom and the dining room. We had the bathroom redone about 3.5 years ago, and the shower over the bath is fitted on that wall plus the bath taps as well. The damp has to be connected to this somehow, do you think?

So does anyone know what kind of tradesperson we need who can investigate and fix it? Do we need to know the exact cause and what sort of cost is typical? Any advice gratefully received!

show us some photos with the damp patch.

How do you ventilate this room?

Hmm, tbh it doesn't really get ventilated. Especially in the winter as that would mean opening the back door.

The pic shows the most of the extent of the damp, except it is now moving along the wall to the left. Te bathroom is the other side of the wall.

Based on what you've said and having seen this kind of damp patch before, I think it's the bath seal where it meets the tiles and/or faulty grouting round the tiles either around the bath seal or below the level of it - water is getting in to the wall that way.

It could also be incorrectly spaced tiles with insufficient grouting so water is getting between the tiles when the shower is used. Water finds the lowest point which is why damage is showing at skirting level.

We get damp in our back bathroom due to condensation collecting on the cold toilet cistern dripping onto the floor (clothes drier is in opposite room and when it is used there is condensation windows etc). However it is an outside wall.

Could there be cold water pipes in the walls behind the damp and their coldness causing condensation on the walls or the toilet cistern against the wall in the other room?

So would you think that taking the side off the bath and having a look ourselves is a good first step?

Yes! What is the condition of the tiles, grouting and bath seal?

Tiles and look ok, but the sealant could be the culprit. My DP has just got the stuff to remove and redo, so that would help.

*and grout

You should have ventilation for your bathroom too, in a bathroom without a window (am assuming from what you say it doesn't have one) you need a really good extractor fan otherwise you will get damp patches and mould not only in the bathroom but in other rooms too especially if the wall is a cold external wall. Good luck.

But have you taken the bath panel off and had a look? You need to properly eliminate the cause. If it's something else or something as well as the bath seal, your putting a sticking plaster on a severed limb as it were.

'you're' obviously

the bathroom has a window and an extractor fan. I haven't taken the bath panel off yet as I haven't the first clue how to do that without damaging it. Also I can't do that until the weekend realistically. We would obvs check before redoing the sealant.

Is it worth trying to work it out ourselves or should we get someone in to do some proper investigation?

I would always try to figure out the problem myself or someone unscrupulous could take advantage and tell it's worse than it is. You think it could be the bath seal, possibly the grouting. If you take the bath panel off and take a look using a torch - there could be dripping from a pipe or something else obvious. If not, is the area just below the bath seal under the bath damp? Are any tiles loose around the bath seal or higher up?

I think there's a leaking pipe in the wall. Stand back and take a wider picture to show bath, shower, taps erc.

The picture isn't of the bathroom, it's of the dining room which shares an internal wall with the bathroom. The plugs are on the internal wall, and the wall on the right is the exterior wall at the rear of our house. You can just see the rear patio door frame on the right.

The bath room shows no visible signs of damp, but it has fully tiled walls so I guess it would be hard to tell.

OK, I still think a leaking pipe in the wall. Unless it is at or below the level where the top edge of the bath meets the wall, which could be leaking sealant. Looking inside the bath panel may give some clues.

You, or a plumber, are going to hack off the tiles and dig it out.

I am especially fond of surface-mounted mixers with surface-mounted pipes because they avoid the need for digging.

I am especially anxious to see signs of water around electrical accessories. It would be useful for an electrician to verify the presence and adequacy of main and supplementary bonding, and RCD protection.

Thanks PigletJohn, that's very helpful. I'm not sure there is a pipe in that wall though, as I don't think the water supply comes from that direction, given what I remember of what was exposed when the work was done.

I think the most important thing is to have a look under the bath and see what's going on. Then we can go from there.