A waterproofing membrane is what keeps a flat roof, a parapet or a balcony dry when paint alone cannot. The main options are torch-on bitumen rolls melted onto the deck with a gas torch, and a fibre membrane bedded into liquid waterproofing coats. Both depend on a primed deck, proper overlaps, sound flashings and falls that take water to the drains. Tell us the roof size and condition, and suppliers near you quote on rolls, primer, tape and sealants. It is free and there is no obligation.
Torch-on or fibre and liquid
- Torch-on membrane: bitumen rolls, often 3 to 4 mm thick and 10 m long, heated with a gas torch and bonded to a primed concrete deck. Rolls with a mineral or aluminium finish resist sun better.
- Fibre membrane and liquid: a polyester fibre fabric bedded into two or more coats of liquid waterproofing. It suits awkward shapes, small roofs and parapets.
- Waterproofing tape: self-adhesive bitumen tape for joints, small cracks, flashings and gutters.
Laying it right
Clean the deck, remove loose material and fix ponding before you start. Apply bitumen primer and let it dry. Lay rolls from the lowest point up so each overlap sheds water, with side and end laps as wide as the roll maker specifies. Turn the membrane up parapets and walls and finish under a flashing or chase. Seal around drains, pipes and corners, and dress the membrane down into the drain outlet so water cannot run under it. With a gas torch, keep a fire extinguisher close, never torch near timber or insulation without care, and check for smouldering after work.
Finding the leak first
Leaks often start at flashings, parapet tops, drain outlets and cracks rather than in the middle of the roof. Repair cracked screeds and loose flashings and check that water drains away. Remember that rising damp in walls is a different problem: a roof membrane does not cure it. For the whole job done by a contractor, compare waterproofing quotes, and for coatings, see waterproof paint.
What it costs
Suppliers quote a torch-on roll (3 to 4 mm, 10 m) at about R1,650, fibre membrane at about R470 per 5 m² roll and bitumen primer at about R875 per 5 L. Add laps when you count rolls, plus primer, tape, sealant, gas and, for fibre systems, the liquid coats. Ask what reflective top coat the supplier recommends for sun protection, and plan to inspect the roof each year before the rains, resealing laps and flashings where they have lifted.
What to include in your request
- Roof area in m² and its falls
- What is on the roof now
- Torch-on or fibre and liquid system
- Parapets, drains and flashings to detail
- Supply only or supply and install
Waterproofing Membranes for different clients
- Homeowners: fibre membrane and liquid coats on a leaking flat roof over a lounge
- Landlords and sellers: waterproofing tape on cracks and flashings before the rains in a rental
- Body corporates and estates: torch-on rolls for the flat roofs and parapets of a block of units
- Shops, offices and restaurants: membrane on the flat roof of a shop or office before the rainy season
- Factories, farms and mines: torch-on and tape for factory flat roofs, gutters and plant room decks
- Builders and developers: torch-on over new concrete slabs and balconies before tiling or handover
- Schools, churches and public buildings: flat roof membranes on school blocks, halls and clinic buildings
- Painters and contractors: rolls, bitumen primer and tape in bulk for waterproofing contractors
Frequently asked questions
Is torch-on better than a liquid waterproofing system?
How much overlap do torch-on rolls need?
What is waterproofing tape used for?
Can I get membrane prices without committing?
Waterproofing Membranes by province and city
- Johannesburg
- Pretoria
- Centurion
- Midrand
- Sandton
- Randburg
- Roodepoort
- Krugersdorp
- Randfontein
- Germiston
- Boksburg
- Benoni
- Kempton Park
- Alberton
- Vanderbijlpark
- Vereeniging
- Durban
- Pinetown
- Pietermaritzburg
- Richards Bay
- Newcastle
- Ladysmith
- Gqeberha (Port Elizabeth)
- East London
- Kariega (Uitenhage)
- Mthatha
- Cape Town
- Bellville
- Paarl
- Stellenbosch
- George
- Worcester
- eMalahleni (Witbank)
- Middelburg
- Secunda
- Mbombela (Nelspruit)
- Rustenburg
- Brits
- Klerksdorp
- Potchefstroom
- Mahikeng
- Polokwane
- Tzaneen
- Kimberley
- Upington
- Bloemfontein
- Welkom
- Sasolburg