Is this rising damp?

[Rees]

Hello, I have several damp patches along our chimney breast and party wall. I think this is rising damp, but I would like a second opinion as most of the patches do not affect the bottom of the wall, and some only appear several feet above floor level. Therefore, I am wondering if the damp could be coming from the chimney/roof. I have attached some pictures, any insight into the source would be much appreciated.

 

[Rob Wheeler]

Hi Rees, as a general rule rising damp doesn't travel up a wall more than approx 1 metre from ground level.
Lack of impervious damp proof courses (DPC) in old buildings are usually the culprit as they used to use slate which could work well but could fail as it was not a continuous damp proof membrane, or I believe even ash as an attempted layer to stop rising damp.

I would think, considering the details you have provided, that this is far more likely to be failing flashing on a chimney stack, alternatively, poor guttering/drain-pipes that are spilling rain water onto exterior walls. This excess of external water can often track though and show as damp patches on the interior plaster finish. This is assuming you have an older property with solid walls and not the more modern cavity walls.

There could also be an issue with your roof slates/tiling that is providing a route for rain water to get into the exterior walls. Again older properties did not have the benefit of water proof membrane under the slate / tile finish.
But I am assuming your property is of a more traditional construction.

Injected wall cures can be a waste of time if there isn't a continuous mortar course into which one can inject a waterproof solution. This is often the case with rubble stone or cob construction.

Sometimes you just have to consider the cost of repair against the problem if at ground level and try interior waterproof coatings of which there are many. Vandex is a cementitious based product and is mixed. then several layers painted on, there are several other brands available.

Also Zinsser manufacture some excellent 'technical' paints (Watertite for example) that can be over-painted once dried.

Long answer as I had some spare time!

But most importantly identify where the damp is coming from which I appreciate is obvious, but the only real way to affect a cure.

 

[CarlH]

Hard to say. You need to ventilate the chimney top and bottom if you block up the fireplace and blank off where the chimney pot was.

If the pot is still there and open, rain will drop down the chimney. If there is no draught up it it will take ages to evaporate, so you need at least an air brick on the outside, as low as reasonably possible, to allow air to ventilate the flue. That should prevent damp accumulating, and not dissipating, inside the flue

One photo seems to be away from the chimney breast and to show damp just above the skirting board., where it is lifting the paint (BTW,in old houses you need porous wall paints, which allow the walls to "breathe") What sort of DPC (dampproof course) does the house have? If it has solid (full brick width) walls, and not cavity walls it should still have a damp course - eg, bitumastic felt, bitumen, blue bricks, slate. If the plaster and skirting board bridge this, damp can travel by capillary action upwards and cross over the DPC into the plaster above it. Sooner or later the skirting board, if timber, will rot, and there will be a smell of mould.