Find the water
before you
treat anything.
Most damp money in London is spent on the symptom. Chemical injections and replastering do nothing at all if the water is arriving from a gutter, a raised path or a failed seal.
Damp is not one
condition.
Rising damp comes up from the ground through the wall by capillary action, and it should be stopped by a damp proof course. It produces a tide mark at a fairly consistent height, usually under a metre, often with salt crystals on the surface and blown plaster at skirting level. It is genuinely less common than the industry implies.
Penetrating damp comes in horizontally through the wall. It is driven by something external: a leaking gutter, cracked render, eroded pointing, a failed window seal, a blocked cavity. It appears as a patch rather than a band, it usually corresponds to weather from one direction, and it moves with the rain.
Condensation is water the building is producing rather than water getting in. It shows as black mould in corners, on cold external walls, behind furniture and around window reveals. It is a ventilation and heating problem, and no damp proofing product will touch it.
These three need completely different remedies, which is why diagnosis is not a formality. A tide mark and a black mould patch in a bedroom corner are not the same problem and they do not share a solution.
Look outside
before you look inside.
Before anyone injects a wall, the external causes are worth ruling out because they are cheaper and far more common. A downpipe discharging onto the ground next to the wall. A path or patio raised above the damp proof course so water simply bridges it. Soil banked against the wall. A blocked gully. Render carried down over the damp proof course.
Inside, the equivalents are a bathroom with no working extract, a tumble dryer venting into a room, and blocked or blanked air bricks under a suspended timber floor. That last one is important because it starves the underfloor void of airflow, and stagnant damp air under floorboards is how joist ends rot.
Any of these will defeat a damp proof course, and none of them are fixed by one. This is why we look at the outside of the building first, and why a quote that arrives without anyone having walked round the property is worth being sceptical about.
Timber decay follows
the water in.
Wet rot is the common one. Timber gets and stays wet, fungus takes hold, and the timber goes soft, dark and stringy. It is localised to where the water is. Deal with the water, cut out and replace the affected timber, and it does not come back.
Dry rot is the serious one and the name is misleading, because it also needs moisture to start. What makes it different is that it can spread through masonry and behind plaster to find new timber, so it travels well beyond the original wet area. It needs proper identification and a wider treatment than simply replacing the visible timber.
Woodworm is beetle larvae in the timber, and the key question is whether it is active. Fresh holes with clean edges and fine dust below them suggest current activity. Old, darkened holes with no dust are frequently historic and long dead, and treating them achieves nothing.
In every case the honest sequence is the same: identify what it is, remove the moisture source, then treat and repair. Anyone quoting treatment before establishing where the water is coming from has skipped the step that determines whether the work lasts.
What your report
probably said.
Reports are cautious about damp because moisture meters give readings, not diagnoses. Typical wording is elevated moisture readings were recorded, further investigation by a specialist contractor is recommended, and no guarantee documentation was available for previous damp proofing works.
The recommendation of a specialist is worth reading carefully. Many damp specialists sell the treatment they diagnose. There is a place for a genuinely independent damp survey, and it is a different thing from a free inspection by a company that installs damp proof courses.
Where a report mentions timber, look for whether it says active or historic. That single word changes the job substantially. And where the report says the sub floor void was not inspected, that is usually a gap worth closing before you buy rather than after.
Questions we get
asked most.
Get a written
price.
Monday to Saturday, 9am to 8pm. All London boroughs.
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Areas we cover.
We take damp and timber treatment work across all 32 London boroughs. Most of our work is in west London, in Shepherd's Bush, Hammersmith, Fulham, Kensington, Chiswick and White City, and in south west London, in Putney, Wandsworth and Wimbledon. We also work in south east London, in Greenwich, Blackheath and Lewisham.
If your property is outside these areas, call us anyway. We travel across London and will tell you honestly if a job is too far to price properly.