Basement waterproofing in London.
Fulham · SW6 · a cast basement slab inside sheet piled wallsOn site, photograph
Waterproofing designed with the structure, to BS 8102, for how the room is used.
Designed with the structure, never added after.
Basement waterproofing keeps ground water out, designed to BS 8102 for the room’s use. We are NU Projects, design and build in Fulham SW6 since 2010. Waterproofing is priced inside the basement build, line by line. Call 020 7731 6841, and a budget estimate typically follows within seven days.
Water in the ground is the main risk to a basement. So waterproofing is designed with the structure, not added after.
BS 8102:2022 is the British Standard for protecting structures below ground from water. It sets three types of protection.
Type A is barrier protection, such as tanking applied to the walls and floor. Type B is the concrete structure itself, built to resist water. Type C is drained protection. A cavity drain membrane leads water to a sump.
The standard also sets grades for the space inside. Living space is designed to Grade 3, the driest of the four.
Where the risk is high, two types are often combined. The 2022 standard expects a waterproofing specialist in the design team.
Pumps, alarms and service access are planned at design stage. Warranty terms can depend on that maintenance.
What the work includes
- Waterproofing designed to BS 8102:2022
- Type A tanking, Type B structure and Type C cavity drains
- Grade 3 for living space, the driest grade
- Sumps, pumps, alarms and backup planned in
- Details drawn with the structural engineer
- A maintenance schedule handed over with the basement
- A project that shows it
- Fulham basements
- Sources
- BSI, BS 8102:2022. The British Standard for protecting below ground structures against water.
- What it costs
- See a range in a minute. Then send us the address for a proper number. Open the calculator
- Where we work
- Fulham, Chelsea, Kensington, Knightsbridge, Belgravia, Mayfair, Notting Hill and Holland Park, Chiswick, Wandsworth, Putney and Barnes, Hampstead and St John’s Wood, Weybridge, Cobham and Oxshott, South Kensington, Marylebone, Bayswater and Maida Vale, Pimlico and Westminster, Battersea and Clapham, Richmond, Twickenham and East Sheen, Islington, Highgate and Primrose Hill, Greenwich, Dulwich, Camden, Wimbledon, Bermondsey, Brixton, Ealing, Acton, Hammersmith and Brook Green, Earl’s Court, Queen’s Park and Kensal Rise, Fitzrovia and Bloomsbury
The room’s use sets the grade. The ground sets the type.
The membrane, before it goes in.
From the ground to a dry room.
- 01
Ground and water
Soil, water table and neighbouring structures investigated first.
- 02
Grade and type
The room’s use sets the grade. The design sets the type.
- 03
Structure and joints
Waterproofing details drawn with the engineer’s structure.
- 04
Drainage and pumps
Sump, pumps, alarms and backup power designed in.
- 05
Installed and checked
Each layer inspected before the next trade covers it.
- 06
Handover and service
The maintenance schedule and records handed over.
Three types of protection, side by side.
From BS 8102:2022. The design decides which type, or which combination, suits the site.
| Question | Type A, barrier | Type B, structural | Type C, drained |
|---|---|---|---|
| How it works | A barrier applied to the structure holds water back | The structure itself resists water | A cavity collects water and drains it away |
| Typical form | Tanking to the walls and floor | Watertight reinforced concrete | A studded membrane, a channel and a sump |
| What it relies on | A continuous, undamaged layer | Concrete design, joints and workmanship | Pumps that work, and are serviced |
| After handover | Hard to reach once covered | Joints must be right first time | Pumps and channels serviced on a schedule |
What owners ask about waterproofing.
Further reading, from the journal
How is basement waterproofing designed?
It is a coordinated specialist design for the intended use and ground conditions. The construction method is designed in alongside it.
Structure, joints, penetrations, drainage and maintenance access all need to work together.
Will a basement need pumps and backup systems?
That depends on the drainage and waterproofing design.
Where pumps are needed, we assess redundancy, alarms and power-loss response. We also plan ongoing access for servicing.
What ongoing maintenance does a basement need?
We follow the actual waterproofing, drainage, pump and ventilation maintenance schedules.
Keep inspection access clear and keep service records. Warranty terms can depend on this maintenance being kept up.
What is BS 8102?
BS 8102:2022 is the British Standard for protecting below ground structures against water.
It sets three types of protection and four grades for the space inside.
What is a cavity drain membrane?
A studded plastic sheet fixed inside the walls and floor.
Water that gets through runs behind it to a channel and a sump.
It is Type C, drained protection, under BS 8102.
What is basement tanking?
Tanking is a barrier applied to the walls and floor to hold water back.
It is Type A, barrier protection, under BS 8102.
Can an existing damp cellar be waterproofed?
Often, yes. A drained cavity system is a common route in an existing cellar.
We check the structure, the water and the drainage first.
What does basement waterproofing cost?
It is priced inside the basement build, line by line, from the design.
Our 2026 cost guide puts converting an existing basement at £180k to £300k.
A new basement dig runs £500k to £900k.
Tell us about the basement.
Your name and one way to reply are enough. It goes straight to the studio.