The shelf where the confusion starts
Walk down the roofing aisle of any large hardware store in Cape Town and you will find four or five buckets with the word rubber on them. Rubberised roof paint. Flexible roof coating. Elastomeric membrane. Liquid rubber. They are next to each other, at prices within a few hundred rand of one another, and nothing on any of the labels tells you which one of them will still be holding water out in eight years.
That confusion is not an accident. Membrane and coating and paint are marketing words in this country, not regulated ones. So the only way to know what you are buying is to ignore the front of the tin and ask two questions: how many coats does it take, and how thick is it when it has cured. Everything else follows from those.
What liquid rubber is
Rubber Sealant® Liquid Rubber is a water-based liquid rubber. It arrives as a thick liquid, you brush or roll it on straight from the drum, and each coat cures by losing water into the air. Three coats, allowed to cure between each, build up to roughly 3mm of continuous flexible rubber.
That 3mm is the whole point. It is not a film sitting on the surface: it is a rubber sheet that happens to have been poured in place instead of rolled out of a factory. It stretches, it bridges hairline cracks, and it moves through the 30 degree daily temperature swing a Cape Town metal roof goes through in February without splitting.
What it is not
- It is not a rubber roof paint. Roof paint is a decorative coating with some flex in it, applied as a thin film. Useful for refreshing a sound roof, useless on a leaking one.
- It is not a structural repair. A sagging purlin, a rotten batten or a perforated sheet has to be fixed before anything gets coated, and any contractor who coats over those is stealing your money politely.
- It is not a one-coat product, however tempting the coverage arithmetic gets at coat two.
- It is not torch-on. There is no flame, no roll, no lap and no gas bottle on your roof.
- It is not a substitute for drainage. Water that has nowhere to go will find the one weakness in anything.
Where it goes
In the Northern Suburbs we put it on metal sheeting, Harvey tile, concrete tile, slate, flat concrete slabs, parapets, boundary walls, box gutters, valleys, balconies, and fibre-cement and asbestos sheeting where the sheets are sound and sealing them in place is the right answer. It also goes over old torch-on, which is one of the most common jobs it does.
What it costs, honestly
| Pack | Price incl VAT | Covers at three coats |
|---|---|---|
| 1 litre | R199 | 1 to 2 m² depending on surface |
| 5 litre | R790 | 3 to 10 m² depending on surface |
| 20 litre drum | R1,990 | 13 m² on slate up to 40 m² on smooth |
Which means product cost lands somewhere between about R50 and R150 per square metre before primer. If somebody quotes you R70 a square metre to waterproof a roof, including labour, you now know enough to work out what has been left out.
Common questions
No pressure
If you would like a second opinion on your own property, we will come and look.
The inspection is free, you get the findings in writing with photographs, and you are under no obligation to do anything with them.