While the rain is still coming down
Stay inside or under cover until it eases, and don't take a ladder to a gutter in rain or wind. If water is getting near light fittings, power points or the switchboard, switch off at the switchboard if it's safe to reach. Keep everyone out of any room where the ceiling is bulging. For urgent storm help, call the SES on 132 500, or 000 if someone is in danger.
What to do tonight
Catch it and clear the area
Buckets, towels, furniture moved, plastic over anything you can't shift. Our first-hour leak guide covers the rest if it's coming in fast.
Film the overflow
From a window or the shelter of the porch, film the gutters, valleys and downpipes while the rain is at its heaviest. Water sheeting over the back of a gutter, a valley spilling sideways or a downpipe that isn't running is the most useful clue a roofer can get, because none of it shows on a dry day.
Note how hard it was raining
Write down the time and whether it was steady rain or the kind that bounces off the road. If the leak only starts once it's really bucketing down, say so.
Check the downpipe outlets at ground level
A downpipe that's dry at the bottom in heavy rain is blocked somewhere above. If the outlet is at ground level and you can clear it by hand, do. Leave anything higher until a roofer can get to it.
Book a roofer for the first dry day
Send them your video. Ask them to check the gutters, valleys and downpipes above the leak before anything else.
Why heavy rain finds gaps that light rain doesn't
Gutters running over the back. Eaves gutters are sized for a certain rate of rain, with a way for overflow to escape outside: slots in the front, a gap behind the gutter, or a front edge set lower than the fascia. The NCC sets these overflow measures for new work. On an older house, or a gutter packed with leaves, a downpour can spill over the back edge, into the eaves and onto the ceiling.
Too few downpipes. The NCC lets each downpipe serve no more than 12 m of gutter and wants downpipes as close as possible to valley gutters. A long run draining to one downpipe, or a corner where a valley empties far from any downpipe, overflows first.
Valleys and box gutters. A valley carries the water from two slopes at once and can spill sideways under the tiles when it's narrow or half blocked. A box gutter sits inside the roof line, so when it overflows the water has nowhere to go but in. Our pages on valley leaks and box gutters go deeper.
Wind with the rain. Downpours often arrive with strong gusts that push water uphill under tile laps and flashings. That's why some leaks only show in storms from one direction.
Low pitch and no sarking. Tiles rely on slope to shed water. Monier's Marseille tile, for example, needs at least 15 degrees with sarking and 20 without, and the NCC requires sarking under all tiled roofs pitched below 18 degrees. An older, flatter tiled roof built without sarking has no second line of defence when heavy rain is driven up under the tiles.
What a real downpour can do
On 6 March 2010, a storm dropped 19 mm of rain on central Melbourne in under 18 minutes, along with hail. About 2,000 homes were damaged, mainly because overloaded guttering led to roof leaks and collapses. Later that month in Perth, hail blocked gutters and drains during a severe storm and made the flooding worse.
Clean gutters help, but no gutter carries everything. What matters is that when it overflows, the water ends up outside the house, not inside it.
Fixes a roofer may suggest
- Clearing gutters, valleys and box gutter outlets, then cutting back the trees that keep filling them
- Gutter guards where leaves are the main problem
- Overflow slots in the gutter front, or a gap behind it, so excess spills outside
- An extra downpipe, or one moved closer to a valley
- A larger gutter where the existing one can't keep up with the roof area
- A wider or replacement valley, or a rebuilt box gutter outlet with an overflow
- Sarking or a re-roof where tiles sit on a low pitch with nothing underneath
Your part, and the roofer's
You can
- Filming overflow from a window or the porch during heavy rain
- Clearing downpipe outlets you can reach standing on the ground
- Booking a gutter clean before the stormy months
- Noting how heavy the rain was each time it leaked
Leave to a roofer
- Clearing valleys and box gutters, which sit on the roof
- Working out whether gutters and downpipes are big enough
- Adding overflow slots, downpipes or new gutters
- Checking for sarking under low-pitched tiles
What we'd do after the first downpour leak
We'd treat it as a drainage problem until someone proves otherwise. Send the roofer your video and ask them to start with the gutters, valleys and downpipes on that side of the house. If the gutters were clean and still overflowed, we'd ask about an extra downpipe or overflow slots rather than paying for another clean and hoping.
Want a roofer to take a look?
Tell us the job and your postcode. We match it with a Find My Roofer certified roofer who specialises in that kind of work, and they call you to quote. Your number goes to them alone.