It held for one winter. That is the tell.
This is the phone call we get most often, and it is nearly always the same shape. The roof was done in spring. It came through the first winter dry, and everybody was happy. Then the second winter it started again, in more or less the same place, and now the contractor is not answering.
Eighteen months is a very specific number and it means something. A system that was never going to work at all leaks in the first month. A system that was done properly does not leak at fifteen years. Failure in the second winter is the signature of a job where the product was fine and something in the preparation, the thickness or the detailing was not.
Almost all of it is diagnosable from the quote you were given, before any work started. Here are the five causes, in the order we find them.
One: the film was too thin
This is the biggest single cause and it is invisible. A liquid membrane performs as a function of its cured thickness. Put on two thirds of the specified material and you get a membrane that looks identical on handover day, survives a mild first winter, and then loses its last bit of margin to ultraviolet light and movement over the following summer.
Two: the surface was never properly prepared
Coatings fail from underneath. A membrane over dust, chalk, lichen, old failing acrylic, or a damp substrate is not bonded to the roof, it is resting on it. Water gets under the edge, the bond releases, and now the membrane is holding water against the roof instead of off it.
- Was the roof cleaned, and how? On tile and metal, a proper wash. On asbestos, low pressure and hand brushing only.
- Was a biocide used and given time to work, or was the lichen just knocked off the top?
- Was a primer specified for that substrate, by name? Galvanised, rusted metal, concrete, fibre cement and old bitumen all need different things.
- Was the roof dry when the first coat went on, and was rain forecast within the cure window?
In Durbanville specifically, the south facing slopes carry heavy lichen because they stay damp all winter under the oaks and pines. That growth is the most common bond failure we find, and it is the step that gets rushed when a crew is trying to finish a roof in two days.
Three: the details were treated as an afterthought
Nothing fails in the middle of a roof. It fails at the upstand, the parapet, the penetration, the box gutter, the outlet, the chimney and the change of level. Those are slow, fiddly, unglamorous work, and they are where the money and the skill go.
A quote that prices your roof as a single square metre rate with no mention of the details is telling you that the details are going to be done fast. Which is exactly why the leak comes back at the same flashing.
Ask a waterproofer to describe how they will treat one specific upstand on your roof. The answer sorts the field in thirty seconds.
Four: nobody diagnosed the leak in the first place
If the water was entering at a cracked parapet capping and the response was to coat the roof field, then the roof got a new membrane and the leak carried on. Sometimes it takes a season for the path to re-establish itself, which is why it can appear to have worked at first.
This is why we will not quote a system before we can state the water path in one sentence. Coating an undiagnosed roof is gambling with your money.
Five: the movement was never accounted for
A metal roof in the Northern Suburbs goes from about five degrees on a July night to sixty-plus on the surface in February. It grows and shrinks measurably every day of its life. Timber decks move with moisture, concrete cracks along its own logic, and every junction between two different materials is a hinge.
A rigid or thin coating over a moving joint gets worked back and forth until it splits. The answer is a genuinely elastomeric membrane at proper thickness, with reinforcing fabric bedded in at the joints and cracks that are known to move. That reinforcement step is cheap, and it is the first thing dropped from a keen price.
What to do about a roof that is already failing
- 1Photograph the failures now, while they are wet. Blisters, splits, debonded edges, and the ceiling stain inside.
- 2Dig out the original quote and look for the spread rate, the number of coats, the primer and the details. What is missing tells you what happened.
- 3Contact the original contractor in writing. Some will come back and honour it, and that is the cheapest outcome available to you.
- 4Get an independent inspection that includes the roof space, and get the water path in writing.
- 5Establish whether the existing membrane can be prepared and overcoated, which it often can, or whether it has to come off. Overcoating a sound but thin membrane is much cheaper than a strip.
- 6Then decide, with a scope that names products, coats, spread rate and every detail.
In a good proportion of these cases the existing membrane is salvageable as a substrate. That is the difference between a repair and starting again.
What we would do on your property
Free inspection, roof and roof space, photographs, and a written diagnosis with the water path stated plainly. Then a scope that lists the preparation, the primer by name, the number of coats, the spread rate, the detail treatment and the guarantee. Flat roofs and torch-on overlay from R265 per square metre, metal and tile from R240, asbestos from R310.
We would rather quote higher and be there in year eight than win on price and be unreachable in year two.
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.