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Damp & Moisture Guide

Understanding Damp, Condensation & Mould

A plain-English guide to how damp actually works – what causes it, how it’s properly diagnosed, and why the right treatment depends entirely on the cause. Written to help you understand your own property, whether or not you ever need us for the work.

Damp Is Not One Single Problem

Moisture can enter, move through, or build up within a building in several different ways. A stained wall, peeling paint, mould or crumbling plaster is a symptom – it doesn’t tell you the cause on its own. Common sources include:

Condensation Penetrating damp Rising damp Plumbing leaks Roof & chimney defects Defective gutters & downpipes High ground levels Bridged damp-proof courses Moisture trapped in solid walls Hygroscopic salts Inadequate ventilation Cold bridging

The Golden Rule

Diagnose First. Treat Second.

A damp-proof course isn’t a universal fix. Neither is tanking, waterproof paint, a dehumidifier, or stripping back the plaster. Each of these solves a specific problem – and does nothing for the wrong one. Current guidance from professional and heritage bodies, including RICS, GOV.UK, Cadw, Historic England and SPAB, consistently emphasises the same principle: find the actual source of the moisture before choosing how to treat it.

A damp patch at the bottom of a wall doesn’t automatically mean rising damp. A damp chimney breast isn’t always a roof leak. Getting the diagnosis right matters – treating the wrong cause means paying for work that won’t fix the problem, while the real cause carries on unaddressed.

The Right Treatment Depends On The Cause

A short guide to what actually fixes what:

Condensation Control moisture production, improve ventilation, address cold surfaces.
Penetrating damp Find and repair the external defect letting water in.
Plumbing leak Repair the leak, then allow the affected materials to dry.
Bridged DPC Resolve whatever’s bypassing the damp-proof course – ground level, paving, render.
Genuine rising damp Address the moisture pathway, with a chemical DPC where genuinely needed.
Defective gutter Repair or replace the rainwater goods causing the problem.
Chimney penetration Repair the stack, flashing, pointing or weathering.
Hygroscopic salts Identify the source, control moisture, remove and replace contaminated plaster.
Cold bridging Improve thermal performance and manage humidity around the cold area.
Blocked sub-floor ventilation Restore proper airflow beneath a suspended timber floor.

Not Sure What’s Causing Your Damp?

Get in touch and we’ll take a proper look before recommending anything – no pressure, just an honest assessment.

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