Why Most Leak Repairs Do Not Hold
A ceiling stains in the corner of a bedroom. A contractor goes up, finds a cracked tile roughly above it, replaces the tile, and invoices. Two months later the stain is back.
Nothing was done wrong except the assumption. Water entering a roof does not fall straight down. It runs along the top of the underlay, down a batten, across a purlin, along the top of a beam, and drops at the first point where something interrupts the run. That point can be several metres from where it came in, and on a different part of the roof entirely.
So the visible damage tells you where the water finished, and almost nothing about where it started. Repairing at the stain is repairing the exit.
This is the single most common reason for repeat leaks, and it is why we treat detection as a separate discipline rather than something you do on the way to a repair.
The Leak Is Almost Never Where the Damage Is
Finding the entry point is a process of elimination, done in a sequence.
Inside first. The roof void tells you more than the roof does. Water tracks leave marks on timbers, and following those marks upslope narrows the search dramatically before anyone gets on the roof.
Moisture mapping. A moisture meter across a ceiling or wall shows the true extent of wetting, which is usually much larger than the visible stain, and shows the direction the water came from.
Thermal imaging. Evaporating moisture cools a surface, so wet areas read differently on a thermal camera. It does not see water directly, it sees the temperature difference, which means it works best under the right conditions and is one input rather than an answer on its own.
Flood testing. Sections of the roof are isolated and water applied in a controlled sequence, starting at the lowest point and working up. When the leak appears, the section that produced it is the section that leaks. Slow, methodical, and conclusive.
Elimination of the other sources. Not every ceiling stain is a roof. Condensation, plumbing, a leaking balcony above, and blocked gutters overflowing behind a fascia all present as roof leaks and are not.
What Usually Turns Out to Be the Cause
Flashings. Where the roof meets a wall, a chimney, a parapet or a dormer. The most common single source we find.
Ridges and valleys. Cracked bedding, missing pointing, corroded or debris-blocked valleys.
Failed underlay. Where the underlay has perished, water that gets past the tiles has nothing stopping it. Common on older Cape Town roofs.
Blocked gutters and valleys. Overflow going backwards behind a fascia board, entering at the wall plate. Presents exactly like a roof leak.
Balconies above. In apartment blocks, the leak in your ceiling is very often the balcony of the flat upstairs.
Condensation. Not a leak at all. Cape Town homes largely have no central heating, so winter condensation in an unventilated roof void or on a cold wall produces damp patches routinely mistaken for ingress.
Horizontal Rain Makes Cape Town Harder
Cape Town winter rain arrives on north-westerly fronts at 50 to 65kph. Rain moving sideways enters at points vertical rain never reaches: under tile overlaps, behind flashings, over upstand terminations, through a gap in a barge board.
That widens the search area considerably compared to a low-wind region. It also explains the most common thing homeowners tell us, which is that the roof only leaks in a storm. A fault that needs 60kph of wind behind the rain to become a leak is invisible for most of the year.
It is also why a leak that appeared in June was often caused by something the December south-easter loosened.
