Seamless Is the Whole Argument
Every sheet membrane has joints, and joints are where roofs leak. Liquid rubber has none. It goes down wet, cures into a single continuous film, and runs straight up an upstand and into an outlet without a seam anywhere.
On a simple rectangle that advantage is modest. On a roof with eight vent pipes, an aerial mount, two plant plinths and a stepped parapet, it is decisive. Every one of those is a detail a sheet system has to be cut and welded around, and every one is a potential failure point.
That is the case for liquid rubber, and on the right roof it is a strong one.
Thin Is the Way It Fails
A liquid system is only as good as the film thickness it cures to, and thickness is where the money is. Spreading one coat where the specification calls for two is invisible on the day and obvious in three winters.
Wet film thickness gets measured, not estimated. A gauge in the wet coating is the only honest check. Coverage rate per litre is the number that matters, and stretching it is the most common corner cut in this trade.
Reinforcement at the details. Upstands, outlets, cracks and junctions between materials need a reinforcing fleece or scrim embedded in the coating. Coating alone across a moving crack will split along it.
Preparation is most of the job. The surface must be clean, sound, dry and primed. Coating over dust, chalking paint or laitance produces a film that peels off in sheets.
It cannot bridge a structural crack. A crack that moves needs a joint detail, not more coating.
Where Liquid Rubber Beats Torch-On, and Where It Does Not
Better on: complex roofs with many penetrations, awkward shapes, box gutters, flashings, roofs where an open flame is a fire risk, and roofs where a lightweight system matters.
Worse on: roofs taking regular foot traffic, roofs that will be tiled or covered, and any surface where consistent thickness across a large area is hard to control.
Torch-on is tougher. Liquid rubber is more adaptable. Neither wins in the abstract.
UV, Salt and the Cape Town Coast
Liquid systems sit exposed, which means UV works on them constantly. Cape Town summer sun and the reflected light off the Atlantic are hard on any exposed coating, and a system that chalks or embrittles will craze within a few seasons.
Salt-laden air on the Atlantic Seaboard adds a second problem. Salt crystallising in a surface film accelerates breakdown, so coastal roofs need a system rated for that exposure and a wash-down as part of routine maintenance.
The summer south-easter contributes too. It is dry, so it will not push water in, but wind-carried sand abrades an exposed coating like fine sandpaper, particularly on the West Coast side.
