Residual Damp and Chimney Breast Damp in a Flat on Sumatra Road, West Hampstead NW6
A property on Sumatra Road in West Hampstead had already had its external render renewed, but the rear bedroom wall was still damp inside. The survey also found a separate problem on the chimney breast in the main bedroom.
Project at a Glance
The Brief
The owner had paid for new external render and expected the damp to clear, but the rear bedroom wall was still showing moisture. They wanted to know what was left to do.
The Survey
In the rear bedroom, the readings showed residual moisture held in the wall from before the external render was renewed. The old internal render had absorbed that moisture and needed replacing.
On the main bedroom chimney breast, the surveyor found isolated damp caused by deteriorated pointing and flaunching on the chimney stack, a form of penetrating damp. The other rooms tested dry.
The Solution
Two separate actions:
- Hack off the damp internal render in the rear bedroom and replace it with new render and set, using a dot and dab board where specified.
- Have a roofing contractor repair the pointing and flaunching on the chimney stack to stop water getting in at the top.
The Work
The internal work in the rear bedroom was completed in one day.
The Result
The owner had a clear picture: the external render had fixed the source in the bedroom, the old plaster just needed replacing, and the chimney needed a roofer rather than damp treatment. See our page on damp proofing in north London.
Frequently Asked Questions
Why is my wall still damp after new external render?
Moisture already in the wall takes time to dry out, and old plaster can stay contaminated. Replacing the internal finish is sometimes needed once the outside is sound.
Can a chimney stack cause damp inside?
Yes. Failed pointing or flaunching at the top of the stack lets rain soak down through the brickwork and show on the chimney breast below.
What is flaunching?
It is the sloped mortar bed around the chimney pots that throws rainwater off the top of the stack.
Damp that will not clear?
Our CSSW and CSRT trained surveyors find the real cause before recommending any work. Non-invasive survey with a clear written report. No obligation.
Survey carried out by Lionel Sewell (FODCS) at Advanced Damp. Project completed in West Hampstead, NW6.
Sam Fitzgerald is the founder of Advanced Damp and a working damp and structural waterproofing surveyor diagnosing and treating moisture problems in residential and commercial properties across London and the South East. He is FODCS certified (a Federation of Damp Certified Surveyor) and a member of the Federation of Damp. His hands-on work covers rising damp, penetrating damp, condensation, basement waterproofing to BS 8102, and thermal imaging surveys, and he has personally completed over 400 damp surveys across properties of every type and age. Everything he writes draws directly from jobs he has carried out. He does not write about treatments, products or causes he has not dealt with first-hand in the field.
