Which system your roof needs
| Roof type | System | Indicative | Service life |
|---|---|---|---|
| Flat concrete deck | Two-layer torch-on membrane | R220 – R380/m² | 15 – 20 years |
| Complex flat roof, many penetrations | Liquid acrylic, fibreglass-reinforced | R120 – R240/m² | 8 – 12 years |
| Trafficable deck or podium | Polyurethane membrane + screed | R450 – R800/m² | 10 – 15 years |
| Sound existing bitumen | Liquid rubber re-coat | R95 – R180/m² | 5 – 8 years |
| Pitched tile roof | Point, seal, replace and underlay repair | Quoted per repair | — |
| IBR / corrugated sheet | Seam sealing and fastener replacement | R80 – R160/m² | 5 – 10 years |
A re-coat over a failed system buys you one winter. If the membrane below is blistered, delaminated or holding water, it has to come off.
Flat roof waterproofing in Cape Town
Flat roof waterproofing is the bulk of what we do, because a large share of the metro's housing and almost all of its sectional-title stock sits under a flat or low-pitch concrete deck. A flat roof has no margin for error: a pitched roof sheds water even where a detail is imperfect, while a flat roof holds it against every fault until one of them gives.
That is why a flat roof is only as good as its falls. A membrane laid over a deck that ponds will fail regardless of the product, the thickness or the guarantee — which is the single most common reason a roof that was waterproofed three years ago is leaking again now.
How a flat roof is done properly
- Strip and inspect the deck. Failed membrane off, screed checked for soundness and for water trapped inside it.
- Correct the falls. A roof that ponds will fail again regardless of the membrane. Screed-to-fall at a minimum of 1:80 toward the outlets.
- Prime. Bituminous primer across the whole deck so the membrane bonds rather than sits.
- First layer torch-on. Fully bonded, 100mm side laps, 150mm end laps.
- Second layer. Laid to break joint with the first so no lap sits above a lap.
- Upstands and details. Membrane carried a minimum of 150mm up every vertical, dressed into outlets, and terminated into a chased and sealed edge.
- Flood test. Outlets plugged, roof flooded, held and checked before anything goes back on top.
Signs your roof needs work now rather than next year
- Blisters or bubbles in the membrane — water is already trapped underneath
- Laps lifting at the edges, especially on the south-east corner
- Membrane gone hard, grey and crazed — the bitumen has lost its oils to UV
- Ponding that is still there 48 hours after rain
- Rust staining or plant growth at the outlets
- A brown ring on the ceiling below that grows every winter
If you already have a stain on the ceiling, start with roof leak repair — the leak is not always above the stain.
Related services
- waterproofing systems
- torch-on waterproofing
- roof leak repair in Cape Town
- waterproofing prices
- choosing a waterproofing contractor
- a free inspection
- contact us
Common questions
How much does roof waterproofing cost in Cape Town?
A two-layer torch-on system on a flat concrete roof runs about R220–R380 per m² including primer and upstands. A liquid acrylic system runs about R120–R240 per m². Access, the state of the existing screed, and whether falls need correcting are what move a quote most.
Can you waterproof over an existing membrane?
Only if the existing membrane is fully bonded, dry, and not blistered. Torching a new layer over trapped moisture drives it into the deck and the new system fails within two seasons.
What is the minimum fall for a flat roof?
1:80 toward the outlets is the practical minimum. Below that a roof ponds, and standing water shortens the service life of every waterproofing system available.
How long does the job take?
A standard domestic flat roof of 60–100 m² is typically two to four working days, plus a dry window before starting. Torch-on cannot be laid on a damp deck.