Damp patch on internal party wall

[Laure]

Hello, we have moved into an older house for a couple of months and noticed a damp patch on the party wall (rear bedroom, Victorian terrace). Any thoughts as to what might be causing this? Roof? The patch was dry September to November and has only recently started to be visibly damp and progressing… what would be the first port of call? Damp survey? Many thanks!

 

[Mr Chibs]

Is the wall to right of the boxed in area an outside wall?

Is there a gutter/hopper/downpipe near this area?

Any idea what's in the boxed in bit?

 

[Laure]

Yes, the wall to the right of the boxed in area is an outside wall. No idea what is in the boxed bit but metal detector beeps there and there is a boiler in the kitchen below. No visible gutter/pipe outside, just vent on neighbour’s wall.

 

[Mr Chibs]

What kind of vent? ventilation or a boiler vent?
If in doubt, take a photo tomorrow.

 

[Laure]

It looks similar to our boiler’s vent but I’ll take a picture tomorrow. Now that I think about it, our boiler is also losing pressure a bit more quickly than it should, although we had it inspected a few months ago, repressurised and flue sealed.

 

[Laure]

Here is a picture of the outside wall from a few months ago. Neighbour’s vent is actually well below the level where the damp patch appeared. Maybe wall crack above is the cause?

 

[Laure]

Hi again, here are some pictures of the outside wall. Any thoughts as to what might cause the damp patch on the party wall? Many thanks!

 

[Koolpc]

If that is a boxed in area then it needs opening up to investigate.

 

[Laure]

Hi, thanks, would you suggest we get a plumber in then? The metal detector does beep around the boxed in area near the damp patch. The area was completely dry in November (although the stain indicated a previous problem there, which we hoped had been solved...).

 

[Mr Chibs]

I'd prise open the boxed in section to have look. Either pipework or cable will be in it.

If this damp patch is up stairs, then the problem could be coming from roof, or cracks in the render.
Have you been in the roof space to have a look at this wall to see if this shows any signs of damp?

 

[Laure]

Thank you for the advice. I could not get into the roof space right above, as there is a dividing wall covered in foil right before the area, and the roof access in the bedroom is sealed.

 

[Mr Chibs]

When you say dividing wall, do you mean the wall between you and your neighbour (party wall)?

You could really do with seeing in the loft, even just to eliminate this as the source. How is the hatch sealed?

I was wondering if condensation could be a culprit behind the foil, but without better photos etc difficult to tell.

 

[Laure]

I meant a wall at the end of the roof space above the hallway, just before you would enter the roof space above the bedroom where the patch is. The hatch is painted over and does not seem to have something to open it but will investigate!

 

[tell80]

OP, How's the investigation! going?

Expand the pic at the top of the crack & you will notice that the wet verge doesn't have a projecting fibre cement undercloak - you will also notice that water staining & just beginning algae(?) can be seen.
This stained area also reaches under the head of the window opening.

Whether any of this is contributing towards your interior damp patch - who knows, perhaps your investigations will help??

 

[Laure]

Hi, thank you! We are getting a damp specialist to have a look next week. If it is the issue you mention, do you have any advice on possible cost/time to sort out? Thanks in advance!

Forgot to mention the damp patch is to the right of the window as you look at it from the outside, so not near the crack that comes down diagonally from the roof to the top of the window. It is on the other side, near the neighbour’s boiler vent.