Project Type
Basement Waterproofing Retrofit
Duration
8 weeks
Recorded Value
£38,000
The duration and value describe this completed project. Your quote will reflect the property, agreed scope and current costs.
Project photographs
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The brief and property
The basement had suffered from persistent water ingress for over 20 years. Previous attempts at tanking with cement-based systems had failed, leaving areas of delaminated render and active seepage. The existing floor level was too low in places for a conventional drain channel detail, and the ceiling height was only 2.1m — borderline for habitable use.
Work completed
A Type C cavity drain membrane system was chosen as the most reliable solution for an existing wet basement. The floor slab was broken up in sections and a perimeter drain channel installed at slab level, discharging to a dual sump chamber with Grundfos pumps and a high-level alarm. The floor was re-laid at the lowest practicable level to maximise headroom. The ceiling was finished at 2.1m with a suspended grid to conceal services.
Results
- Type C cavity drain system installed — independently inspected and certified
- Dual Grundfos sump pumps with high-level alarm and battery backup
- Basement converted from unusable to dry usable space
- 45m² divided into study, utility room, and plant room
- Ceiling height achieved: 2.1m throughout
- Six-month post-completion monitoring confirmed zero water ingress
- No planning permission required — works entirely within existing footprint
Key Features
- Type C cavity drain membrane — full perimeter and floor
- Dual Grundfos sump pumps with battery backup
- New floor slab at optimised level for maximum headroom
- Suspended ceiling concealing cavity drain membrane and services
- Utility room — new WC, laundry plumbing, and electrical board
- Independently certified by waterproofing specialist surveyor
Specification
| Item | Specification |
|---|---|
| Cavity drain membrane | Delta MS Drain, 8mm studded HDPE, full floor and perimeter walls |
| Sump system | Dual Grundfos Unilift CC 7 pumps, 300L GRP sump chamber, float switch alarm |
| Floor slab | A142 mesh reinforced C25 concrete slab, 100mm, DPM below |
| Ceiling | Metal grid suspended ceiling system, 30mm cavity, Gyproc tiles, 2100mm finished height |
| Wall finish | Delta PT membrane plaster base, Gyproc Thistle bonding coat and skim |
| Electrics | New consumer unit, LED downlighters, double sockets throughout, IP65 to wet areas |
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