Damp Walls advice sought

[lewie]

Fair. It's a bodge.

You’ll trap the moisture - op needs to find the source

[Mouse]

That leadwork looks a right mess (imo). I reckon that'd be a good place to start.

[funkstar]

General guidance is to look for the cause to be able to find a solution. General defects that lead to moisture in buildings to look for

1 Understand what causes deterioration of building fabric including, for example, the
following:
• porous materials
• freeze and thaw cycles, wetting and drying cycles, soluble salts
• organic growth (including moulds)
• non-porous materials
• corrosion of metals
• timber: insect infestation and decay.
2 Understand the main mechanisms of dampness in buildings
3 Be able to recognise and identify evidence of infestations by the most commonly encountered wood-destroying insects, and take steps to determine whether the infestation is active.
4 Be able to identify the most common forms of wood-decaying fungi that affect buildings, and understand the conditions necessary for growth.
5 Understand how past interventions and consequential changes in the building could influence moisture accumulation in the fabric.
6 Understand why dampness may be manifest in a building
7 Understand sources of dampness, ventilation, heating and insulation positions/types and the impact these have on moisture levels.
8 Understand the reasons for surface mould and condensation in buildings.
9 Understand the significance of salts in assessing moisture problems, how salts can move through the building fabric and how this might influence a resistance meter. Understand how such salts can damage building materials.
10 Understand the potential effects of some impermeable wall and floor coverings.
11 Consider the influence of existing external ground levels, drainage, cold areas and ventilation.

[wildheart]

I have similar issue's in my extension. As an ex roofer I understand capillary attraction which is a nightmare with free standing kerbs covered by lead or chimneys. My situation is being caused by us not heating the extension. Dehumidifiers are fantastic especially if you are using the radiators for drying? When I decorated I used rock wall insulation wall covering, it has heated the wall I struggle with up a hell of a lot. Our climate is very tricky to manage unless you have the heating on all the time.

[eddie1]

Thanks again everyone for giving me some very helpful advice on this.

Those of you pointing to the Lead work being part of the Cause are on the right track.
I crawled up into the attic today and the chimney stack and wall directly underneath the photo showing the exterior chimney and lead work is dry but the area below the lead work ( hidden behind plasterboard in the loft extension)
is clearly wet so it would seem that the lead work is directing the water in and under the roof tiles.

So the starting point would seem to be to get a good roofer to come and replace that lead work/flashing.
Any other advice on what else should be done when the roofers here much appreciated.
if that is the only source of water ingress then hopefully replacing that will fix it and I wont need to go down the route of membranes etc.

That wall does get all the weather (as can be seen in the pics before rendering) and as it never gets full sun doesnt get much time in the year to dry out.

[Casper]

You’ll trap the moisture - op needs to find the source

Agreed.
Looking at those pictures the outside wall and chimney stack seems to be getting very wet. I don’t know why this is. Is the rain water then soaking through the render and the brick?