Why Are Your Gutters Overflowing? What Causes It and Who Fixes It

Usually because they're blocked. A gutter full of leaves and sludge can't carry storm water to the downpipe, so it goes over the edge instead. The fix is a gutter clean. If your gutter's clear and still spills, the problem's somewhere else, and the table below shows where to look.

It tends to show up in a summer storm. A lot of water comes down the roof in a few minutes, and a gutter that's half full of leaves has nowhere to put it. A light shower might drain away fine. That's why a blocked gutter can go unnoticed until the first big storm of the season.

You can usually tell from the ground. Look for plants growing out of the gutter, leaves poking over the edge, or water pouring over the front when it rains. Stains or water marks on the wall under the gutter line are another sign. If you can see plants growing out of it, you're past due.

Trees make the biggest difference. A gutter under gums or palms fills far sooner, while a house under open sky can go a lot longer between cleans. Here's how often to clean your gutters, depending on what's overhead.

Look past the gutter itself. The downpipe might be blocked further down, even when the gutter looks clean. The gutter might have lost its slope, so water sits instead of running. Or it's too small for your roof in a big storm. The last two are jobs for a licensed roof plumber.

Downpipes are the easy one to miss. Gum nuts roll to the low point of the gutter and wedge in the downpipe outlet, out of sight from the ground. Silt and fine leaf pack down there too. The gutter looks fine, but the water can't get out, so it backs up and spills near the downpipe.

Slope is next. A gutter has to fall gently toward its downpipe so the water runs to it. If the gutter has sagged or lost that fall, water sits in the low spot, and in a storm that's where it spills first.

Then there's size. If a clear gutter only overflows in the heaviest rain, it may be too small for the roof, or there may not be enough downpipes to take the water away. Working out what your roof needs is a roof plumber's call.

They can. When a gutter can't drain, water can go over the fascia (the board the gutter's fixed to) or back under the roof. From there it can reach the eaves, or show up inside. That's why it's worth sorting out an overflow before the next big storm, even if it only happens a few times a year.

Where the water goes depends on the house. Take the post-war homes on Brisbane's northside. They have deep, timber-lined eaves, so the water tends to run back behind the gutter into the fascia instead of spilling off the front. On a two-storey home, the overflow can be hard to spot from the ground.

Suncorp warns about it too. Its guide to blocked gutters says that before long, you could be “battling leaks, cracks, moisture and dampness in the ceiling”.

Overflow does damage outside as well. On a flat block, the water that spills off the gutter lands against the slab and in the garden beds instead of running away. On a sloping block it runs, and it takes the mulch with it.

Keep the gutters and downpipes clear before storm season, because that's when they get tested. If trees fill your gutters fast, one clean a year may not keep up. That's where gutter guard helps: it keeps leaves out, so the gutter stays clear between cleans. If the gutter's too small, that's a job for a roof plumber.

The Queensland Government makes the same first point. Its list for preparing your home (opens in a new tab) says to “clean gutters and downpipes so water can drain away as quickly as possible”. It also says the best time to get ready is before storm, cyclone and monsoon season. Our storm season checklist goes through the rest of that list.

Under big gums, a clean helps for a few weeks. Then the trees start again. For roofs like that, we fit leaf guard over existing gutters, and every install starts with a free gutter clean.

One thing guard can't do is make a small gutter bigger. If yours spills in a big storm even when it's clear, get a licensed roof plumber to look at the size before you spend money on anything else.

Then the leaves may not be the whole story. Gutter guard keeps leaves out of the gutter. It can't clear a blocked downpipe, fix a gutter that's lost its slope, or make a small gutter carry more water than it was built for. So check the other rows of the table above.

If you think the guard itself is causing it, ask whoever fitted it to come back and take a look. Our guide to gutter guards in heavy rain covers why water can run over the top.

It depends on your insurer and your policy, so check yours before storm season. Suncorp's own page (opens in a new tab) says “Suncorp Home Insurance does not cover damage caused by blocked gutters.” Other insurers may word it their own way. Read your policy, or call your insurer and ask.

While you're at it, check how much you're covered for. The same Queensland Government list says to make sure your home and contents insurance is up to date and covers enough.

Call us when the gutters are full of leaves and sludge. We clear the whole run, then check that water gets to the downpipe. If your gutters are clear and still overflow, a licensed roof plumber is the right call, and we'll tell you if that's what we see.

We clean gutters on their own across Brisbane, the Sunshine Coast and the Gold Coast, and you don't need gutter guard to book a clean. We've been family-owned for over 25 years, and we're fully insured. The quote is free, and you'll have the price before we start.