Damp

[appletreeinthesun]

Our house has a wierd two story extension that is I think single skin. It was there when we bought it. There is a patch of damp in the back corner of the downstairs room and on the front wall of the upstairs one. The upstairs room smells musty when it rains.

Is this penetrating damp? What can I do about it?

You need @PigletJohn the most knowledgeable person on MN. Have you got some photos you could upload? Is there dripping guttering above that corner or a drain near the area?

Thanks! I'm away at the mo but will ask DH to photograph. There is a pipe outside the first but no obvious leak

Upstairs is under a bedroom window

upstairs room is probably a leak, either roof or plumbing. Sometimes from badly fitted windows.

Downstairs patch is most likely waterpipe or drain

None of these causes will be repaired by chemical injections.

Need photos inside and out, especially of drains and gutters.

How old is the house, how old is the extension, do you think it had Building Regulations approval.

Thanks @PigletJohn it's a thirties house with a very old extension, but no issue with building regulations when we bought it so I don't think so. It's actually hard to tell that it was extended, it looks like part of the house.

I'll ask DH to send some photos when he gets back.

is there a flat roof? How old?

Thanks @pigletjohn we don't know when it was added, it looks as if it's part of the house. It's very odd.

It's worse than I thought :-( the first set of pictures are the corner of the downstairs room and the downpipe outside.

And here's upstairs- the first picture is the front top corner (usually hidden in a cupboard), the second is a patch under the window and the final one is the outside.

Forgot to say, no flat roof, it's pitched and tiled

there is a square thing in the wall near the downpipe. Is that to a chimney in the wall?

The ceiling with paper hanging off if most likely a roof leak. Have a look in the loft. There might perhaps be some plumbing up there. Take some photos that show the pitch of the roof and the gutters as well as the pipe.

The downstairs corner is most likely a water pipe or drain. Show the outside walls at ground level, especially any gullies or pipes, and any airbricks. Look for the DPC which is probably a line of slate in the mortar bed 9 inches above where ground level used to be when the house was built.

Does that room have a concrete floor, or wooden with a void beneath?

Indicate the positions of bathrooms, kitchens, and other rooms containing water.

What is that thing with a fold-down door?

Thanks this is incredibly helpful.

Both the square thing on the outside wall and the drop down thing upstairs are air vents.

Downstairs is on a wooden floor, the garage is below (no insulation)

I'm still away so will take pictures when I get back tomorrow morning.

@PigletJohn just coming back to update you with apologies for it taking so long.

A builder came and had a look and said the damp could be from the down pipe or from the flat roof at the back of the garage which I hadn't thought of as it's not over the damp itself. Basically damp might be seeping along the wall. It's a very complicated and unusual layout.

Upstairs apparently looks like condensation.

Thank you so much for your advice, it was so helpful, really appreciate it.