Damp Proofing a Lower Ground Garden Flat on Medley Road, West Hampstead NW6
A lower ground floor garden flat on Medley Road in West Hampstead had both rising and lateral damp. The building had solid 9 inch brick walls and no damp proof course, and the ground next door sat higher than the flat.
Project at a Glance
The Brief
The owners had damp at low level through the garden flat and wanted a clear plan that dealt with the cause, not just the plaster.
The Survey
The flat is at lower ground level with solid 9 inch brick walls and no damp proof course. The survey found both rising damp and lateral moisture coming through the walls from the ground outside.
At the front, the render was defective, there was a gap at the door threshold and the pointing had deteriorated. The right flank wall sits against higher ground in the neighbouring garden and garage area, which holds moisture against the brickwork. The report was clear that these external defects had to be dealt with first.
The Solution
A staged specification, outside first:
- Install an ACO drainage channel to take surface water away from the base of the walls.
- Repoint the deteriorated brickwork.
- Damp proof the affected internal walls once the external work was in place.
The Work
The work ran from 12 to 27 October 2026, combining the drainage, repointing and damp proofing into one programme.
The Result
By fixing the drainage and pointing before the internal treatment, the new damp proofing is not left fighting a constant supply of water from outside. Garden flats in the Edwardian streets of West Hampstead and Kilburn often sit below neighbouring ground in the same way. See our page on damp proofing in Kilburn.
Frequently Asked Questions
What is lateral damp?
Lateral damp is moisture moving sideways through a wall from higher ground or soil on the other side, rather than rising up from below.
What does an ACO channel do?
It is a surface drain set into the ground along a wall. It collects rainwater and runs it away, so water does not pool against the brickwork.
Why do the external repairs come first?
If water keeps getting into the wall from outside, internal treatment will struggle. Fixing the source first protects the new work.
Damp in a garden flat?
Our CSSW and CSRT trained surveyors find the real cause before recommending any work. Non-invasive survey with a clear written report. No obligation.
Project completed by Advanced Damp 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.
