Flat roofs · Guide
Torch-On vs Liquid Waterproofing: Which Is Best for Your Roof?
Quick answer
Torch-on membranes are usually best for flat concrete roofs that hold ponding water, lasting about 10–15 years. Liquid membranes (acrylic or polyurethane) suit roofs with lots of details, foot traffic or tight spaces. Acrylic lasts about 5–10 years; polyurethane about 15–20 years.
Both systems work. The question is which one suits your roof, budget and how long you want it to last.
Side-by-side comparison
| Torch-on | Liquid acrylic | Polyurethane | |
|---|---|---|---|
| Typical price per m² | R250–R450 | R150–R350 | R350–R500 |
| Typical lifespan | 10–15 years | 5–10 years | 15–20 years |
| Ponding water | Good | Poor to fair | Good |
| Foot traffic | Fair (with protection) | Poor | Good |
| Complex details | Harder | Easy | Easy |
| Needs gas torch | Yes | No | No |
Ranges from published 2026 South African cost guides. See our Pretoria price guide.
Choose torch-on when…
You have a flat concrete roof, water tends to stand after storms, and the surface is sound enough to bond to. It's the standard for flat roof waterproofing.
Choose liquid when…
The roof is full of upstands, pipes and corners, it's a parapet or coping, the existing coating is sound, or you're sealing laps on an IBR roof. For balconies people walk on, polyurethane is the better liquid.
What matters more than the product
Preparation, primer, overlaps, detailing at outlets and parapets, and a UV-reflective finish. A great membrane badly installed fails sooner than an average one installed well.