Penetrating Damp from Coping Stones on New Road, Northchurch HP4
A house on New Road in Northchurch, near Berkhamsted, had damp at high level in a conservatory style dining room. The cause was rainwater getting in through failed pointing on the coping stones above.
Project at a Glance
The Brief
The owners had damp showing in the upper part of the dining room wall.
The Survey
Outside, the pointing on the coping tiles and a section of brickwork to the right of the guttering had deteriorated. Rain was getting through those joints and soaking into the upper part of the internal wall, a classic case of penetrating damp.
The Solution
Stop the water, then repair the wall:
- Rake out and repoint above and below the coping stones and the front brickwork.
- Remove the damp plaster and apply a salt neutraliser.
- Render and skim to a finish ready for decoration.
The Work
The work was completed over two days in May 2026.
The Result
With the coping joints sealed, the dining room wall can dry out behind its new finish. See our page on damp proofing in Berkhamsted.
Frequently Asked Questions
What are coping stones?
They are the capping on top of a wall or parapet that throws rain off. If their joints fail, water runs straight into the wall below.
Why neutralise salts?
Damp leaves salts in the masonry. A salt neutraliser and the right render stop them spoiling the new plaster.
Can damp at the top of a wall be rising damp?
No. Damp at high level is almost always water getting in from above or from outside.
Damp high up on a wall?
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 Northchurch, HP4.
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.
