Waterproofing
Cavity-drain membranes
Maintainable cavity-drain membrane systems assessed for suitable basement and cellar projects.
Why diagnosis matters
Treat the cause, then repair the damage
A cavity-drain system manages water behind an internal membrane and directs it to a suitable discharge. Design must include drainage routes, access, pumps where needed and future maintenance.
Technical review
Dan, Director / Surveyor
Last reviewed: July 2026. Advice is general until the property, access and visible evidence have been assessed.
Guarantee & aftercare
Written guarantee terms are matched to qualifying work, with inclusions, exclusions and aftercare explained before acceptance.
What we consider
Possible causes and lookalikes
Groundwater entry
Unreliable barrier substrate
Complex junctions
Need for a maintainable system
Inspection method
A clear work sequence
Step 1
Survey and define design responsibility
Step 2
Plan drainage and discharge
Step 3
Install and test components
Step 4
Issue maintenance requirements
Scope boundaries
Honest about what the work does—and does not—cover
Pumps, alarms, backup, discharge and structural waterproofing design require verified specialist competence and insurance.
Common questions
About cavity-drain membranes
Where does the water go?+
It is directed through channels to gravity drainage or a sump and pump, depending on site conditions and approved design.
What happens if the pump fails?+
Risk controls can include alarms, backup or battery provision. The design and maintenance plan must address this.
Can channels be inspected?+
Maintainable designs include access for servicing and flushing.
Related services
Continue your investigation
Next step
Claim your complimentary survey before choosing a treatment
Tell us what you can see, when it changes and where the property is. Photographs can help us triage the next step.