Cellar Tanking vs Type C Drainage: Which to Choose for Your Basement

SANS 10400-J + SANS 10252 gives three categories of basement waterproofing. Choosing between them — and combining them — is the difference between a dry useful basement and a R1,000k remediation in five years.

The three SANS 10400-J types

• Type A: Barrier protection (membranes, applied tanking)
• Type B: Structurally integral (waterproof concrete)
• Type C: Drained protection (cavity drainage to a sump)

Type A: Tanking

Coatings or sheet membranes applied to the structure to block water ingress.

Cementitious tanking

Brush-applied cement-based slurry. Cheap, but failure-prone at joints and movement areas. Generally not recommended as sole protection for habitable spaces.

Self-adhesive membranes

Bitumen-based sheets stuck to substrate. Better than cementitious for joints, but tricky on irregular substrates.

Liquid-applied membranes

Polyurethane or polyurea coatings. Excellent for complex geometry. Vulnerable to substrate movement.

Type B: Waterproof concrete

Engineered concrete mix with low permeability and crack control reinforcement. Joints, penetrations, and construction defects are where it fails — design and workmanship determine performance.

Type C: Cavity drainage

Studded plastic membrane creates a drainage cavity between structure and finishes. Water that does penetrate flows down the cavity, into a perimeter drain, to a sump, and is pumped out.

• Accepts that some water will get in
• Most robust for habitable basements
• Requires ongoing sump pump maintenance and battery backup

Combined systems

SANS 10400-J strongly recommends combined protection for Grade 3 environments (habitable). Typical combinations:

• Type B + Type C — most common for new-build basements
• Type A + Type C — common for retrofit

Single-system protection on a habitable basement is a major insurance risk.

Grade of protection

• Grade 1: Some seepage acceptable (car park, plant room)
• Grade 2: No seepage but tolerant of damp (workshop, store)
• Grade 3: Dry, controlled humidity (habitable spaces) — combined systems required

Specialist sign-off

Basement waterproofing must be designed by a appropriately qualified Waterproofing Design Specialist. Insurance and warranty providers (Local Authority, NHBRC enrolment) increasingly require this. Don't accept contractor-designed systems without specialist input.

Cost

• Cementitious tanking: R600–R1,400 per m²
• Membrane tanking: R1,200–R2,400 per m²
• Cavity drainage system (Type C): R1,600–R3,200 per m²
• Combined Type B + C: R3,000–R6,000 per m²

MCFAR works with appropriately qualified specialists on South African basement projects.

Frequently Asked Questions