Could it be salts?

[Lotte]

As I said before the pointing has been redone and wall has been waterproofed. The chimney was also re flashed 2 years ago. It is capped. Let me know if you have further questions

 

[ree]

Thank you for the pics.

The gable is the side wall in question as google would have told you.

I can't see a terminal of any kind on the c/stack (FWIW the stack has been lowered) which means none of your flues are top ventilated unless air bricks have been used?

Waterproofing, to my mind, is a waste of time - it quickly weathers away.

The rear view shows what appears to be a sand and cement fillet on your stack - it should be lead flashing.

The lower adjoining roof is butting against the gable wall, and also has a sand and cement fillet instead of lead flashings.

S&C fillets are v. bad building practice and usually crack and allow water to penetrate.

There is a large moisture(?) stain on the gable brickwork in the front elevation pic.

Given the rough focus (fuzzy and dark) and lack of projection, the pics dont tell me much more about the pointing?

 

[JohnD]

looking at the front view, I wonder if the terrace was originally built like that, or the end was demolished, for example after war damage?

The gable wall looks as if it has had water where the lower roof meets it. Good leadwork will prevent that. Black paint is not so good.

You say the chimneys are capped, so they might not have through ventilation. Hold a joss-stick or cigarette in front of the air vents and see if there is a draught sucking up the chimney (there should be). You can unscrew the grilles and have a sniff for damp if you like. If that turns out to be the trouble, it is possible to ventilate the tops with an airbrick, or even drilling into the flue from the loft, if you are certain the fires will never be used again. If you are considering spending money on the chimneys, ask about having them taken down below the roofline and the slates/roof reinstated above them. I have known this save a lot of future leaks and maintenance on chimneystacks, and the flues can be left open.

Without being there, I'd be inclined to think that it is rain getting in round poor flashing. This should be visible in the loft. If you know a keen photographer with a telephoto lens they might get some closeups of the stack and the gable wall. I can see it will be awkward to get to. I had a roofer round yesterday who tells me he will have to hire a cherrypicker for a day.

If you are really lucky and it turns out to be condensation that will be easier. A bit of damp in the flue will evaporate away with good airflow.

edit
I agree with Ree that lead is what you need, not s&c, if that's what it is. Any builder can do mortar, but good leadwork needs a bit of skill. Lead would last about 30 years, but less than 100.

p.s.
I think the gutter has been leaking or spilling out of the end

 

[Lotte]

Hi both

Thanks for your comments. I fear I need a better camera to do it justice.

I really think the joss stick idea is smart. Thanks

Jon you are right about the history. We believe our house was never intended to be end of terrace and a bomb took out everything on the other side!!

Regards the flashings - it's all lead - including the lower wall which has just been redone. Specifically the roofer took off the sand fillets, maybe it is the quality of my photo

The stain question is of interest - will try and sort some better photos .

So - neither of you consider this could be a salts issue?!

Lotte

 

[ree]

Current pics in daylight are best.

Salts could be still coming through and salts could have remained in any gypsum plaster.

All remedial plastering requires a sand and lime render - never use gypsum plaster.

OP, if you continue your thread please collate your replies, otherwise its v. difficult to follow you.