Help! Damp!

[InsolentAnnie]

We have a 1930s house with a modern extension. Damp has appeared over the past year: mould in the corner above the skirting boards (goes up a foot or two), and a dark patch that goes across the wall to the chimney breast - the slate hearth looks slightly darker on one side too. In the other front room there’s a damp patch on the chimney breast (which doesn’t have a fireplace or air brick) which gets worse when it rains, and a couple of other darker patches on internal walls which are behind furniture.

My thoughts are rising damp in the first room (or bridging of the damp proof course), and penetrating damp due to no ventilation of chimney breast in the second room - not sure about the other patches in that room, maybe condensation? We do have a DPC that the previous owners had injected but maybe it’s been bridged.

So - who on earth do I get to look at this? Do I pay for a specialist damp company to do a survey, and not have a clue whether they are being truthful about the amount that needs doing? Or do I get some sort of other independent surveyor in? I don’t know who to call! Any advice much appreciated - thank you!

Pictures up to the gutters please.

Are the floors concrete?

Open the lid of the water meter please and photograph what you see. There may be a glass dial with an air bubble turning in it. You may need to clean off the dirt. There may be a blue T handle.

I see a white strip round the outside of the house which I think conceals the original DPC. Look for any point where this has fallen off and exposed the slate or other material. Is there any difference in dampness or colour of bricks above and below this strip?

It is most unlikely that the DPC itself has "failed."

It's possible that rain is collecting in loose patches behind the render and getting into the cavity. Have a look at the brick pattern on the outside. Are the bricks alternately showing sides and ends, or are they all sides except where a half has been used to make up a length?

I enlarged the pics on a bigger screen, and I think the bricks at the base of the chimneybreast are wetter (darker) than the bricks beside them, and have a whitish bloom of efflorescence, which is dissolved lime left behind when the water evaporates. It can come from tapwater in hard water districts, but also from rain that has passed through building materials such as mortar and concrete.

The chimney is unusual since it projects from the wall on the outside of the house, and also on the inside to give a chimneybreast. There seems to be a ledge high up on the outside that might be allowing rainwater penetration. Probably when the house was built it had sloping mortar on top, or a slab, which for best work would have had lead flashing let into the brickwork. Lead lasts maybe 30 years so this could be a cause of the defect. A roofer might repair it, but leadwork is now specialised enough that they may call in a local lead worker for a skilled job. Any signs of repair with mortar, bituminous paint or sticky tape indicate a bodge that is pretty sure to have failed.

Additionally, I see no airbrick in the bricked-up fireplace to ventilate the chimney. This is necessary because sealed chimneys accumulate internal condensation, though yours is worse than that. If you have the opportunity, have someone make a brick-sized hole just above the skirting. You can look and sniff inside, and put your hand in to see if it is wet, and if builders have shovelled rubble into the cavity (which also encourages damp). You can put a plastic or brass vent grille over the hole later.

I don't see any airbricks in the pics, suggsting it is a concrete floor. I have a feeling that the source of water is making the floor wet, which could explain why walls are showing damp patches in various places. The parquet is probably laid on bitumen or a modern membrane to prevent damp reaching it. It will swell and rise up if it gets damp.

I can't tell yet if the water is coming from the chimney (probable), the render (possible) or a water pipe under the floor or in a wall (possible).

Since the house was built with a DPC which is well above ground level (although it has been mortared over), in your case, I think it probably isn't coming from the ground. But rake back the gravel and see how wet the ground is.

Keep track of dampness and weather to see it it worsend during or after rainy spells. Or if it comes on after you'd had a bath or shower. You can draw round the patches with a pencil and write the date to see when they grow or shrink.

It's not condensation, though extra ventilation will help dry it out.

Thanks so much - this all makes a lot of sense. I think the floor is concrete, as it sounds pretty solid. Parquet is definitely laid on bitumen. The previous owners did inject a damp proof course above the original one - I think you can see the plugs in the mortar. They did the windows themselves (not brilliantly) and I did wonder if water might be getting in at the base of the window - you can see it’s a bit of a bodge job in the bottom corners. The upstairs windows had this which is think is what caused the yellow fur on DD’s wall! The bricks seem to show sides, except on one line of them on the chimney in the blue room, which rather oddly shows sides and ends. I think the line up to the ceiling in the blue room that you mean is a shadow. There are no pipes under the floor; they all run along the skirting boards. Which makes it quite odd that the internal walls between the blue room and the hall are damp..?

The odd ledge bit has never had a cover on it; we have seen the original architect plans for the house. Next door gives you a better idea of what it looks like (our tiles on the slope have been painted over - not by us) as theirs is properly painted!

I think I can see a dark patch on or by the ledge on one of the houses, which might mean water is lying on it or penetrating.

The water supply pipe probably runs under the house, usually in a straight line between the outdoor stopcock or water meter, and the place where the kitchen sink used to be when the house was built. In your case though it might be in the side alley.

Water pipes usally last around 50 years.

Yours might be an iron one.

I wondered about the windows, but the amount of wet you have is more than expected. however if they are DIY fit they might be worse than usual, and you have wet patches seemingly unconnected to the windows.

As you have seen, the silicone injections do no good at all.

Thanks so much @PigletJohn - that gives us much more knowledge to work with. Who should I get to come and look at it - what sort of surveyor, and is there an approved list so I can make sure I get someone properly qualified?!

A chartered surveyor has a wide knowledge of building defects.

Many small local builders will be familiar with the repairs you need, but diagnosis has to be performed and verified first to ensure the true cause is known.