Damp
Telling them apart.
The pattern, the height, the timing and the salts. Four pieces of evidence that between them account for nearly every damp wall in Wales.
Diagnosis
Rising damp
- Defined horizontal tide line, typically 0.5–1.2 m
- Hygroscopic ground salts present in the plaster
- Constant through the year rather than after rain
- Often traced to raised external ground, a bridged or rendered-over course, or a blocked sub-floor vent
Where a chemical course is genuinely warranted we install one and re-plaster to a salt-retardant specification. Where it isn't, we say so and tell you what the wall actually needs.
Diagnosis
Penetrating damp
- Localised patch, any height, worst after driving rain
- Traceable to a defect: cracked cement render, open joints, failed pointing, split downpipe, slipped slate, chimney flashing
- Impermeable render or plastic paint on a solid stone wall, holding water in
- Exposed western and south-westerly elevations taking the brunt of it
The fix is nearly always building repair rather than chemical treatment — which is why our report tells you what to instruct, not what to buy from us.
Diagnosis
Condensation & mould
- Black spot growth in corners, on cold reveals, behind furniture and inside wardrobes on external walls
- Worst in winter, worst in bedrooms and bathrooms
- Driven by cold solid-wall surfaces, moisture production and too little ventilation
- Frequently made worse by sealing up an old building with new windows and no added ventilation
We measure surface temperatures and humidity, identify the cold bridges, and specify ventilation and heating improvements. No chemical treatment resolves condensation.
Diagnosis
Plumbing & defect leaks
- Sharp, contained, often below a bathroom or kitchen
- Flat roofs, box gutters, valley gutters and shared rainwater goods on terraces
- Ingress from a neighbouring property in a terrace or flat
- Frequently mislabelled as rising damp because it presents low down
Identifying the true source matters commercially as well as technically: it determines whether the cost sits with you, a neighbour, a freeholder or an insurer.
The Welsh case
Cement render is the single biggest cause we find.
A pre-1919 Welsh wall is typically solid rubble stone bedded in lime, with no cavity and no damp-proof course. It manages water by absorbing it and releasing it again — the lime mortar and lime render are the drying mechanism, not a defect in it.
Coat that wall in a hard cement render and a plastic masonry paint, and two things happen. Water still finds its way in through shrinkage cracks, failed junctions and the top of the render. And once in, it can no longer evaporate out through the face, so it travels down and sideways and comes out inside.
On a meter that presents as a broad wet band low on the wall — which reads exactly like rising damp, gets treated as rising damp, and returns within a year or two because the actual cause was never touched.
One visit
Stop guessing at the cause.
We measure it, trace it, and put the reasoning in writing.