Caution
A hygrometer and a log of when the damp appears tell you more than one damp meter reading. A survey puts the evidence together, and the answer decides whether you need ventilation or building work.
Contact the installer first and check the guarantee paperwork. A damp survey should find the cause before the insulation is blamed or removed.
Damp in an extension is often at the join with the old house or in a floor that has no working membrane. The builder or building control sign-off may help.
The cupboard under the stairs is often the coldest, least ventilated part of the ground floor, over a floor nobody dampproofed. Find out whether it is condensation, the floor or a leak.
A damp ground-floor slab usually has no damp proof membrane, or a failed one. Lift a corner of the covering before deciding between a membrane and a leak.
A new house holds a lot of building water, and it tends to be airtight. Some damp and condensation in the first year is common, but a persistent patch is a defect to report.
Describe the job and get a fixed price from a local damp proofer.
