How can you explain this damp problem?

Question

There is an irregular water mark stretching either side of my chimney breast on the ground floor - its definatley not rising damp as it only appears midway up the wall (about 30 cm from the ground) - we've had the place professionally dampcoursed, as did the people before us. The plaster was left 20 cm or so off the ground and we've put the skirtings on correctly. The damp appears no where else in the house. We live in a midterrace Victorian cottage. I've noticed it has got worse lately with the rain - our neighbours don't have any such problems and we are stumped. Can anyone explain this????

We have had the chimney professionally capped. The cement around it on the roof looked fine.

Answer 1

Sounds like you've go damp trapped. Has the pot on to of the stack been capped, if it has it must be vented to allow moisture to escape. I take it the fire is not in use, so have you got an air vent in or just above the skirting? This is essential to allow air to circulate in the breast. Don't expect it to clear overnight, it will take about a year especially as winter is coming. If you treat the inside with a liquid waterproofer you can apply it with a hand sprayer but cover the area by at least a foot all round.

Account to follow.

Answer 2

So, you've had 2 professional damp proofings...I'd look to the chimney then

Is it still used ? If not I'd get it vent-capped, and maybe look at the external pointing as well. don't block the top of the chimney, but put a rain deflecting cap on it.

if the bottm of the chimney is blocked it, maybe drill acouple of holes in the blanking plate, there may be water trapped above it and its seeping through the chimney breast.

Its not likely to be the flashing as you'd see that in an upstairs room but it might be worth having a look around the loft.

Maybe its damp caused by condensation. The chimney will be colder so there might be a cold stop cuasing condensation thats soaking into the wall. It wold not necessarily show as droplets like condensation on a window.

30cm up the wall is a typical place for rising damp to appear so I don't know why you dismiss that.

Victorian house will be solid walls, so the damp could be rising us the internal brick course and then tracking across where mortar brided the 2 courses.

Answer 3

You say your neighbours don't have any problems, but you don't know that for sure. Have you been up on the roof and looked at the chimney? Have you inspected the flashing's etc? Are there broken or cracked tiles? Are your rainwater pipes in good order.?Are the gutters clean and hoppers unblocked.
There are so many reasons you could be having this problem, but my suspicion is that water is running into the inside of the chimney somehow. It's so hard to know exactly without looking.
You really need someone who is skilled enough to see where the problem might be stemming from.
Sorry I can't be more helpful. Good Luck.

Answer 4

On lots of old terraced buildings you get slight crack in the brickwork, especially around the chimney because of it's structure. The terraced house I used to live in was extremely close to a WW2 blast that left a crack down the side, and I used to get some damp. I would suggest laying some damp-proof sheets over the wall render and then plasterboarding. This means that it'll be much cheaper to take off again if the damp comes back through. Hopefully the sheets will stop the board from getting damp. If not, then maybe you need to get someone onto your roof to see if the water is coming into the loft.

Answer 5

I would put it down to rain entering the flue from down the chimney pot or the cement work at the base of the pot
as the flue rises from the fireplace it changes direction at about a 30 degree slope the water then hits this so a damp patch or the other thing could be birds nest blocking the flue
remedies ;- sweep chimney for birds nest then have
the pots vent capped of and cement work looked at

Answer 6

Hi, it is probably rain coming down the chimney, unlike what most people think the chimney breast does not come down in a straight line. It comes from the roof with usually 2 inner brick square tubes. one will come straight down then 45 degree bend for about a meter and then 45 degree back to the up stairs fire place. Then you will have exactly the same for the down stairs. The 45 degree bend is about 1/2 meter from the top of your fire place, so if the water comes straight down it will then slow down and trickle on the 45 degree bend but will not get to the bottom as the bricks will absorb the moisture.

Answer 7

Have you check the inside of your chimney? Sometimes when chimney are made the masonry does not coat the inside of the chimney with no leak seal to stop water from sliding down the chimney. You will need ti have your chimney clean professional and ask them to check the inside to made sure that they are no cracks or holes in the linning which would let water come throw and travel down to your ground floor.

Answer 8

Could there be something bridging the cavity which allows the damp to travel through the wall ?
Also , get someone to check the lining on the chimney just in case water is going down it and penetrating through the walls.

Answer 9

Discreetly fix an air vent low down on the chimney breast,one with a closing vent.Your chimney needs to breathe,so if the chimney pot is completely sealed off,change it for a vented one,easily obtained at builders merchants.Once you got it breathing again it will take afew weeks before it dries out so be patient,

Answer 10

A wild guess: some rain gets into the chimney somehow?