Line of damp running above damp-proof course

[mixedpeel]

Well, maybe not the right description, but it runs above the new plaster of a damp proof course, around the chimney breast and some of the wall of our back room.

I say new, the damp proofing was done when we first moved in 13 years ago, but this line of crumbling plaster appeared after about 5 years I think.

Time to do something about it, but I'm hoping it's not chop it all off and start again.

Anyone know?

Do you still have your damp proof course guarantee?
If you do, is it still within the guarantee?
Without seeing the problem, it does sound like it has failed. Sorry.

Lots of threads on here about damp. Get a builder to have a look at the outside, especially the roof and the flashing round the chimney stack. Rising damp, which most damp proof courses as sold as a 'cure' for, is rare. More likely that the actual cause of the damp wasn't fixed properly and moisture making its way down is hitting the chemical damp proof course and can go no further so is coming through the plaster.

If it's above, it could be water dropping down the cavity (as it should) but then the dpc isn't sloping outwards, doesn't have a cavity tray. The water should be directed to the outside but if it isn't it will penetrate through.
I only know this because our builder did it wrong so they had to correct it! John

Thanks for all your replies, yes I do still have the guarantee (25 years), but I was hoping for some thoughts before getting back in touch with them.

Your responses are really useful, to help me assess whether I get told a load of flannel by whoever comes round.

Totally agree, rising damp is very rare. If it was rising damp it would only extend 2-3 brick coarses up the wall (so I've read)

We had 'rising damp' in our lounge (one wall and inglenook). Two damp proof specialists- one said rising damp, the other brick salts. Period property repairer also said rising damp.

None of them were right. It was condensation! Rest of house has cavity insulation (lounge is old part so solid walls) and double glazing everywhere.
So all the humidity was going through to the coldest room, the lounge, and condensing on the walls and being sucked in by the salts from our fire place and next doors chimney breast.
We have now had a wood burner burning in there, evenings only since beginning of December (as well as radiator obviously) also bought a couple of unibond Aero 360's to catch humidity.
We had a diagonal line going up the wall to the corner - all damp. And bricks crumbling in the inglenook from the damp.

All the damp has gone! No line on the wall or damp crumbling bricks, so relieved and a bit chuffed I've saved us some expensive messy 'wrong' repairs.

Houses have to breath, especially old houses. They were not built for modern living, drying in doors, cooking and all the draft proofing we do.

Is the room the damp is in noticeably colder then the rest of the house? If so condensation could be the problem if so it will be a much easier fix - and a much cheaper one!

One question I should have asked earlier. What type of house do you have? Mid or end terraced, semi?

Testificate, it's a 1930s semi.

WhatDoIKnow, very useful food for thought in your post, thank you. This is indeed the coldest room in the house, north facing, plus has a 70s extension with a concrete floor. Until a couple of years ago, the end wall was entirely secondary glazing, in various (slightly bizarre) sections, and was pretty much glued/painted shut, so very poor ventilation. That has improved since we put in patio doors with Windows either side, so easy to just open a window, or in warm weather, have the patio doors open.

We have a gas fire in the hearth, but infrequently used.

I'm now wondering whether removing the crumbling plaster, then really focussing on ventilating and keeping it a bit warmer might actually solve the problem. We have a dehumidifier so that could go in there too.

PS I'm thinking the damp proof companies must be in cahoots with mortgage providers. How many thousands (millions??) of people must have had installing a new damp proof course as a condition of the mortgage, as we did? I wonder how many houses genuinely benefited from it.

(I don't really mean to suggest a conspiracy, btw. Just very convenient for the damp proofing people that it comes up on surveys so frequently, isn't it!)

A damp survey should be done be an independent surveyor who is familiar with local property construction and will give an independent view on damp issues and how to fix them. Too many people get their initial survey report back and see a damp survey is recommended (most of the time this is just backside covering by the first surveyor) then look for free or cheap damp surveys because they have already paid out for the first survey and are totting up what their solicitor's fees are, etc. and moving house is an expensive business.

Lo and behold, the surveyor who works for the damp proofing company recommends a chemical damp proof course and either the vendor or the buyer pays for it in order for the deal to proceed.

Ah, wowfudge, I think that's exactly how it happened with us. Hm, I'll be a lot less naive should we ever move again, and get a properly independent survey done.

Does the wall feel damp to the touch?

photos please

I suppose you mean a chemical injection treatment?

Most likely whatever was the source of water before, is still there now. Time to find out what it is and cure it.

Is this an outside wall? Photograph the outside as well please, and put your finger on the height where the inside is wet.

Watching with interest - I have similar, yet to get to bottom of.