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Penetrating Damp Treatment in London
Damp patches that grow after heavy rain, wet plaster around chimney breasts and damp walls in lower ground floors are usually penetrating damp. We find where the water is getting in and stop it at the source.
What Causes Penetrating Damp?
Penetrating damp is water moving sideways through a wall from outside. Common causes in London properties are:
- leaking or blocked gutters and downpipes
- cracked render and eroded mortar joints
- defective chimney flashings and missing chimney caps
- bridged or debris-filled cavity walls
- earth or pavement against walls of lower ground floors, vaults and cellars
Below-Ground Penetrating Damp
When the wall is below ground level – a basement, cellar, vault or lower ground floor flat – fixing the outside is often impossible. Here damp proofing alone is not enough and the wall needs structural waterproofing designed to BS 8102:2022: cementitious tanking (Type A) or a cavity drain membrane system with a sump pump (Type C). As CSSW-qualified surveyors we design and install both. See Basement Waterproofing.
How We Fix Penetrating Damp
- Survey – moisture mapping inside and inspection outside to trace the water path.
- Repair the source – gutters, pointing, render, flashings or cavity defects.
- Let the wall dry and replaster – with breathable or salt-resistant plaster as needed.
- Waterproof below ground – tanking or cavity drain membrane where water pressure is present.
Areas We Cover
We treat penetrating damp across London – from Victorian terraces in Hackney and Islington to mansion flats in Westminster and Kensington & Chelsea – plus Berkshire and the Home Counties.
What Our Clients Say
Book A Damp Survey
Damp after heavy rain or in a lower ground floor? Book a damp survey and we will trace the source and give you a fixed quotation. Call 020 3432 4842.
