Why your roof leaks in the rainy season
Gauteng's rainy season runs from October, and that is when roofs that were quiet all winter start to leak. This guide explains the faults that fail when it rains, and why the wet patch on the ceiling is usually not above the entry.
The season finds the weak point
A roof can look sound all winter and leak in the first hard storm, because most roof faults only show when enough water arrives. A hairline crack in a tile, a fading seal around a fastener, or mortar that has perished along a ridge will hold through a drizzle and fail under a Highveld downpour. The summer storms arrive from October and run through the season (source: JT Roofing).
Wind makes it worse. Rain driven sideways reaches places that vertical rain never touches: under a lifted flashing, past a parapet, or up the underside of an overhang. That is why a leak that appears in a storm is often a detail failing, not a hole in the field of tiles.
The faults that fail first
Flashings lead the list: around a chimney, a vent pipe, a parapet or the joint where the roof meets a wall. Next are the ridges on a tiled roof, where the bedding mortar cracks and lets water along the ridge line. Valleys, where two pitches meet and the most water runs, fail when they block or lift. On metal sheeting, perished washers and loose fasteners let water in at the laps.
Below all of that, blocked gutters and valleys are the fault that costs least to fix and is most often ignored. When the drainage is full, water backs up under the roof edge or pools on a flat section, and it looks like a roof failure when it is really a maintenance one.
Why the wet patch is not above the entry
Water that gets in does not fall straight down. It runs along a rafter or the underside of the sheeting and drips at the first place it can, often metres from where it entered. So the wet patch above a window may be fed by a fault at the ridge or behind the chimney. That is why a contractor reads the roof rather than the ceiling.
It also means a leak can be working for a long time before it is seen. Water soaking into a ceiling, insulation or a wall does quiet damage first; the visible stain is the late stage.
What to do when it leaks
Stop the water, then fix the cause. A temporary measure to protect the ceiling is reasonable while the roof is wet; a permanent repair in the rain is not, because most systems need a dry surface. Note where the water appears and when it appears - only in heavy rain, only with wind, or every time - because that pattern helps the contractor find the entry.
Then get the roof looked at properly. A contractor traces the water uphill of the wet patch, checks the details and the drainage, and quotes the repair. If the roof has several faults, the honest answer may be to waterproof the roof rather than chase leaks one at a time.
Why the same roof leaks every season
A roof that leaks every summer usually has more than one fault, or one fault that was patched rather than fixed. Water that was stopped at a flashing can move to the next weak point, and a coating that has reached the end of its life will keep letting water through wherever the surface is thinnest.
That pattern, a leak in a new place each season, is the signal that the surface as a whole needs attention rather than another patch. One repair is a repair; a roof that leaks yearly is a roof asking to be waterproofed properly.
Frequently asked questions
Why does my roof only leak in heavy rain?
Some faults only take water when the rain is hard or wind-driven enough to push past a flashing or an outlet. That usually points to a detail rather than a hole.
Can I find the leak myself?
You can note the pattern and check the obvious things, like blocked gutters. Finding a hidden entry usually needs someone on the roof, which is not a safe job without the right equipment.
Should I repair or waterproof?
If one detail has failed, repair it. If the coating or membrane has worn across the roof and the leaks keep moving, waterproofing is the honest fix.