Damp/stain upstairs outside wall; wall doesn’t feel damp but gets darker in patches when it rains Damp can be a major issue in the home. Find answers to questions or post your own here.

[ChrisLou]

Scaffolding up for third time on side of house. Chimney checked and appears sound and has been thoroughly treated with Storm Dry. Outside wall re-pointed and had layers and layers of Thompson’s damp proof added. Guttering sound, no sign of any damp/leak in loft. Roof sound. Granite house, inside wall has no mould despite the patches. Cob inner wall we think. But the wall does look patchy and dries out when we have long period of dry weather. Would appreciate any help. Thankyou

[stoneyboy]

Hi chrislou
The most likely reason for damp ingress is that you have non porous granite with presumably mortar joints and no cavity. Rain gets into the joints and soaks through to the inner wall but this will only occur on the sub standard mortar joints. Short of forming an internal wall and cavity there is little you can do.
Regards S