Low-level staining or tide marks
Marks, salts or damaged plaster near floor level can be associated with ground moisture, but plumbing, external ground levels and contaminated plaster must also be checked.
What a useful investigation should establish.
A proposal is more useful when it explains the likely cause, the evidence, the affected construction and why a particular repair is being considered.
- Map the pattern, height and timing of visible moisture rather than relying on one meter reading.
- Inspect rainwater goods, plumbing, external defects, ground levels and possible bridging of the existing DPC.
- Consider wall construction, previous renders or plasters and whether the building uses permeable traditional materials.
- Differentiate rising damp from penetrating damp, condensation, below-ground water pressure and salt contamination.
Options, not assumptions01 02 03 04
How the repair may be approached.
Remove the moisture source first
Repair leaking services, rainwater defects, defective pointing or raised ground levels where these are responsible.
Chemical damp-proof course where appropriate
An injected system may be considered for confirmed rising damp in suitable masonry. The drilling pattern, material and installation method must match the wall construction.
Compatible plaster reinstatement
Salt-affected plaster may need removal and replacement with a specification suited to the wall and chosen damp-proofing system.
Drying, ventilation and monitoring
Walls need time to dry. Finishes should not be reinstated before the background is ready, and traditional buildings may require vapour-permeable materials.
Important limitation
A chemical DPC is not a universal answer. It is not the correct treatment for condensation, active rain penetration, a plumbing leak or walls under below-ground water pressure. In solid-wall and traditionally constructed buildings, incompatible impermeable materials can also trap moisture and should be considered during diagnosis.
