A
Type A — Barrier
A separate waterproof barrier resists water passing through the treated surface. This includes suitable cementitious tanking and membrane systems.
Structural waterproofing specialists
Basement Waterproofing in South West London & Surrey
Sika cementitious tanking, cavity drainage membranes and sump pump systems for cellars, basements, retaining walls and other below-ground spaces.
- BS 8102 principles
- Type A & Type C solutions
- South West London & Surrey
Design around the structure and risk
Waterproofing basements and below-ground walls
Below-ground rooms face a different moisture risk from ordinary walls. Water may act against the structure through the ground, so the specification should consider construction, visible entry points, groundwater risk, drainage, intended use and the consequences of failure.
Depending on the property, an appropriate design may use Type A barrier protection, Type C drained protection or, where justified, combined systems. Type B relates mainly to a structure designed and built to resist water through its own fabric.
BS 8102 waterproofing types
Type A, Type B and Type C protection
B
Type B — Integral
The structure itself is designed to provide water resistance, commonly through reinforced concrete design, joints and controlled workmanship.
C
Type C — Drained
A cavity membrane manages incoming water and directs it to drainage, gravity discharge or a sump-and-pump arrangement.
BS 8102:2022: The standard describes protection of below-ground structures against water ingress. The labels refer to protection strategies, not simply three product brands.
Type A waterproofing
Sika cementitious tanking and waterproof render
A suitable multi-coat cementitious waterproofing system can form a continuous bonded barrier across prepared masonry, junctions and detailed areas. Substrate preparation is critical: weak plaster, contamination, loose backgrounds, cracks and service penetrations can compromise a barrier.
- Basement and cellar walls
- Retaining walls and below-ground masonry
- Wall-to-floor junction detailing
- Crack and penetration preparation
- Waterproof backgrounds for suitable finishes
- Project-specific preparation and application
Type C waterproofing
Cavity drainage membranes and sump pumps
A Type C system allows moisture to enter the original structure but controls it within a cavity behind a studded membrane. Water is collected through suitable channels and directed to a safe discharge.
Where gravity drainage is not available, the design may include a sump and pump. Channels, inspection points, alarms and pumps should remain accessible, and planned maintenance is part of the protection strategy.
Typical Type C components
- Studded wall and floor membranes
- Maintainable perimeter drainage channels
- Inspection and cleaning points
- Sump and pump where required
- High-level alarm or backup provision where specified
- Planned servicing and maintenance access
At-a-glance comparison
Choosing between waterproofing types
| Type | How it works | Typical use | Key consideration |
|---|---|---|---|
| Type A | A barrier is bonded or applied to resist water. | Existing or new below-ground walls where the system and substrate are suitable. | Continuity, preparation, detailing and substrate condition. |
| Type B | The structure itself is designed to resist water. | Commonly new reinforced-concrete below-ground construction. | Structural design, joints, concrete specification and workmanship. |
| Type C | Water is collected and safely drained behind a cavity membrane. | Basement refurbishment and new below-ground work. | Drainage routes, pump provision, access and ongoing maintenance. |
General guidance only: A project-specific design should consider the building, groundwater, intended internal environment and the consequences of water ingress.
A controlled installation
From waterproofing survey to completed system
Inspect
Assess construction, water entry, cracks, ground levels, junctions and available drainage routes.
Specify
Select an appropriate Type A, Type C or combined strategy for the intended use and risk.
Prepare & install
Prepare backgrounds, detail penetrations and install the agreed waterproofing components.
Test & explain
Check the completed work and explain drying, finishes, access and maintenance requirements.
Basement waterproofing near you
South West London and Surrey coverage
Atruss Preservation carries out waterproofing and tanking work in Wimbledon, Raynes Park, Tooting, Wandsworth, Earlsfield, Southfields, Putney, Clapham, Battersea, Richmond, Kingston, Sutton, Carshalton, Epsom, Reigate and nearby areas.
Related damp services
Connected property preservation work
Waterproofing FAQs
Questions about basement waterproofing
What are the three waterproofing types in BS 8102?
Type A is barrier protection, Type B is structurally integral protection and Type C is drained protection. Each uses a different strategy for resisting or managing groundwater.
Is Sika cementitious tanking Type A waterproofing?
A suitable cementitious multi-coat system can provide Type A barrier protection when correctly designed, prepared, detailed and installed for the project.
What is the difference between tanking and cavity drainage?
Tanking normally resists water with a bonded barrier. A Type C cavity drainage system instead manages water behind a membrane and directs it to drainage or a sump pump.
Which system is best for an existing basement?
It depends on construction, groundwater risk, substrate condition, drainage, intended use and consequences of failure. Existing basements commonly use suitable Type A or Type C systems; some projects justify combined protection.
Does Type C waterproofing need maintenance?
Yes. Drainage channels, sumps, pumps and related components should remain accessible and be inspected and maintained according to the system design and manufacturer guidance.
Do you waterproof basements throughout South West London?
Yes. We cover Wimbledon, Wandsworth, Tooting, Earlsfield, Southfields, Putney, Clapham, Battersea and surrounding parts of South West London and Surrey.
Need advice about a damp basement or cellar?
Call Atruss Preservation to discuss an inspection and appropriate waterproofing specification.