Got mould creeping through your gutters? You’re not alone. All it takes is a bit of moisture, some built-up leaves, and a lack of sunlight, and before you know it, your gutters are looking more like a science experiment. The good news? You don’t need to call in the big guns just yet. With the right know-how and a bit of elbow grease, you can clear out the mould growth yourself and stop it from coming back. We’ve been cleaning gutters across Melbourne since 2007, so we’ve seen every kind of mess you can imagine — and we know exactly what works (and what doesn’t). Cleaning doesn’t have to be a chore, and we’ve asked our Melbourne gutter cleaners to share their best DIY tips to help you tackle the job with confidence.
In this guide, we’ll show you why mould takes hold in the first place, how to spot the early warning signs, and the best DIY methods to clean it out — whether you’re going the natural route or using heavy-duty cleaners. We’ll also cover how to protect different gutter materials, easy ways to stop mould from coming back, and when it’s time to call in a pro. Ready to get stuck in? Let’s do this.
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What causes mould in gutters?
Mould doesn’t just show up out of nowhere — it needs the right conditions to take hold. And gutters, if they’re not properly maintained, can be the perfect breeding ground. The main culprits? Damp leaves, standing water, poor drainage, and a lack of sunlight.
Leaves and debris are a big part of the problem. As they accumulate in gutters over time, they trap moisture, creating a damp, shaded environment where mould thrives. That’s why it’s so important to keep your gutters clear. We’ve put together some handy tips on how to keep leaves out of your gutters to help you stay on top of it. But even if your gutters look clean, poor drainage can still lead to standing water, giving mould and mildew plenty of time to spread. Blocked downpipes, sagging gutters, and even an uneven roofline can all cause water to sit where it shouldn’t. On top of that, if your gutters are shaded for most of the day — whether from overhanging trees or the shape of your roof — they don’t dry out properly, making the problem even worse.
Sorting these issues early makes a huge difference. Regular maintenance and smart prevention go a long way toward keeping mould out of gutters for good.
Signs you’ve got a mould problem
Not sure if your gutters have a mould problem? It’s not always obvious at first, but there are a few telltale signs to look out for. The sooner you spot them, the easier the fix.
The most obvious sign is black, green, or white patches along the inside or outside of gutters. Black mould is the most common, but green mould and white mildew are just as troublesome. If you see black streaks or blotches that keep coming back even after a bit of rain, that’s a red flag.
Another giveaway is a musty smell around your gutters or downpipes. A mould stain doesn’t just look bad — it has a distinct, damp odour that lingers. If you catch a whiff of something earthy or stale when you’re outside, especially after a wet spell, mould could be to blame.
Then there’s the issue of blocked drainage and overflowing gutters. Mould thrives in damp conditions inside of your gutters, and if your gutters aren’t draining properly, it’s a sign that something’s not right. Leaves and grime lead to clogged gutters, giving mould the moisture it needs to spread. If you notice water spilling over the sides every time it rains, it’s time to take a closer look.
Catching these signs early can save you a heap of trouble down the line. A bit of mould is easy to deal with, but if it’s left too long, it can spread, damage your gutters, and even find its way into your home. Best to nip it in the bud before it becomes a bigger headache.
A clog is the least of your worries — why mouldy gutters are a big deal
Mouldy gutters aren’t just ugly — they can cause real problems if you leave them too long. What starts as a few patches of mould can quickly turn into damage that’s expensive to fix. Gutters are meant to keep water flowing, but when mould and moisture build up, they start to break down. Over time, that can lead to rust, cracks, and even roof damage. Worse still, the mould doesn’t always stay put. Spores can spread through the air, affecting both your home and your health.
Here’s why removing mould immediately is always the way to go:
- They damage gutters and roof materials: mould and water damage lead to rust, cracks, and costly repairs, not to mention the dangers of the degrading structural integrity of your roof.
- They can affect your health: mould spores in the air can trigger allergies and respiratory issues.
- They make your home look neglected: dirty, streaky gutters bring down your home’s street appeal.
Sorting out mould early is always the best move. A simple clean-up now can save you a lot of hassle (and money) down the track.
What you’ll need to clean mould out of your gutters
Before you get stuck into cleaning, it’s worth making sure you’ve got everything you need. A bit of prep work goes a long way in making the job easier, safer, and more effective. You’ll want the right tools to clear out the grime, plus a cleaning solution strong enough to get rid of mould without damaging your gutters.
Tools & equipment checklist
Here’s what you’ll need to get the job done properly:
- Sturdy ladder with a stabiliser: Keeps you safe while working at height.
- Gutter scoop or trowel: Makes clearing out debris from your gutters quick and easy.
- Scrub brush with stiff bristles: Helps loosen stubborn mould patches.
- Garden hose or pressure washer: Rinses away dirt and leftover cleaning solution.
- Bucket or spray bottle: We recommend a sprayer with an adjustable nozzle — it’s a great and portable way to mix and apply your cleaning solution.
- Gutter vacuums: A great way to clean gutters from the ground, allowing you to remove leaves, dirt, and mould without climbing a ladder. They’re effective, but not vital.
- Protective gear: Gloves, a mask, and safety glasses to keep you safe from mould spores and chemicals.
The right chemicals for mouldy gutter cleaning
Not all cleaning solutions work the same, and what you use depends on the level of mould buildup — and what your gutters are made from.
- Natural options: Vinegar, bicarb soda (baking soda), and oxygen bleach are all great ways to clean light mould and are safe for plants and pets. A vinegar and water mix is a simple, effective solution for regular maintenance; mix one part vinegar to one or two parts water, though you can dilute as much as you feel is right.
- Stronger mould removers: Chlorine bleach or commercial mould killers work best for heavy mould buildup but need to be used carefully, especially around plants.
- Best options for different materials:
- Plastic gutters: Stick to gentle cleaners like vinegar to avoid damage.
- Aluminium gutters: Avoid anything too acidic — rinse thoroughly after cleaning.
- Steel gutters: Use a rust-inhibiting cleaner and make sure to dry them properly afterwards.
With the right tools and chemical gutter cleaning product, you’ll be ready to tackle mould head-on and get your gutters back to top shape.
Step-by-step guide to cleaning mould out of your gutters
Cleaning mould out of your gutters isn’t just about scrubbing until it disappears. To do the job properly — and make sure the mould doesn’t come straight back — you need the right approach. Follow these steps for a thorough clean that keeps your gutters in top shape.
Step 1: Set up safely
Before you even think about grabbing a brush, make sure you’re set up properly. Gutter cleaning means working at height, so safety comes first.
- Secure your ladder properly. Use a ladder with a sturdy stabiliser and place it on solid, level ground. If you’re on soft ground, put a board underneath the feet for extra stability. If possible, have someone hold the base for added security.
- Wear the right gear. Mould spores aren’t something you want to be breathing in, and the last thing you need is chemical spray in your eyes. Gloves, a face mask, and safety glasses are all must-haves.
- Check the weather. Avoid cleaning on windy days, and don’t attempt this job during or after heavy rain — wet gutters and roofs are a slipping hazard. A dry, mild day is best for getting the job done safely.
Step 2: Remove debris first
Mould loves damp, organic material, so the first step is clearing out anything that’s built up in your gutters.
- Scoop out the bulk of the gunk. A gutter scoop, trowel, or even an old plastic container works well to remove leaves, twigs, and built-up sludge.
- Flush out the smaller bits. Once most of the debris is gone, a garden hose can be an effective way to remove anything left behind. Pressure washing is even better — just be careful not to use too much force, especially on older or plastic gutters.
Getting rid of debris first makes sure your cleaning solution actually reaches the mould instead of just sitting on top of dirt and leaves.
Step 3: Apply your cleaning solution
With the gutters cleared, it’s time to hit the mould with your chosen cleaner.
- Spray or scrub, depending on the severity of the mould. If it’s only light, a vinegar or oxygen bleach solution in a spray bottle should do the trick. For heavier mould, use chlorine bleach or a commercial mould remover.
- Let it sit for 10-15 minutes. This step is key — don’t rush it. Letting the cleaner soak in properly gives it time to break down the mould so you’re not scrubbing twice as hard later. If it’s a warm day, you might need to reapply to keep the surface of your gutters damp while it works.
Step 4: Scrub away the mould
Now for the elbow grease.
- Use a stiff-bristled brush to remove stubborn patches. Work in small sections, scrubbing in circular motions to lift the mould off properly. If you’re dealing with a lot of grime, don’t be afraid to reapply your cleaning solution as you go.
- Rinse thoroughly. Once the mould is scrubbed off, use your garden hose or pressure washer to wash everything away. Pay attention to the downpipes — if mould has been growing there, it could clog up your drainage if you don’t flush it out properly.
Step 5: Inspect and repeat if needed
With the main scrubbing done, take a step back and check your work.
- Look for any leftover mould spots. If some stubborn areas of your gutter remain, apply another round of cleaner and give them another go.
- Check that water is flowing freely. Pour some water through your gutters and downpipes to make sure there’s no blockage. If water is pooling anywhere, you might have a sagging section that needs fixing.
Taking the time to do a final check will ensure that your gutters are clean and working properly.
Cleaning different gutter materials the right way
Not all gutters are built the same, so it pays to know what you’re working with before you start scrubbing. Plastic gutters are the most delicate — stick to soft brushes and gentle cleaners to avoid scratching or weakening them. Aluminium gutters can handle a bit more scrubbing, but acidic cleaners like vinegar can cause damage if they’re not rinsed properly. Steel gutters are the toughest of the lot, but they’re prone to rust, so be sure to dry them off once you’re done. A little extra care now means fewer problems down the track.
How to keep mould from coming back
Cleaning mould out of your gutters is one thing — keeping it from growing back is another. A bit of regular maintenance and some smart prevention can save you from dealing with the same problem over and over.
Keep gutters clean year-round: The best way to stop mould from coming back is to keep your gutters free of the damp, organic debris that helps it grow. A good rule of thumb is to clean your gutters at least twice a year, but if you’ve got a lot of trees around, you may need to do it more often. We’ve put together some handy tips on keeping your gutters clean all year round to help you stay on top of it.
Improve sunlight and airflow: Mould thrives in damp, shady spots, so increasing sunlight and ventilation around your gutters makes a big difference. Trim back any overhanging branches that keep your gutters in constant shade, and consider installing wider downpipes to help water drain faster and keep things dry. To avoid major build-up, regularly clean your gutters at least twice a year, or more often if you have overhanging trees.
Use mould-resistant coatings: If you want to go a step further, applying a mould-resistant spray can help prevent regrowth. These treatments create a protective layer that makes it harder for mould spores to take hold, especially in gutters that tend to stay damp for longer.
Install gutter guards: Gutter guards won’t stop mould entirely, but they do a great job of reducing the amount of debris that collects in your gutters. Less leaf buildup means less moisture trapped in your gutters, making it harder for mould to grow in the first place.
A bit of prevention now will save you time and effort down the track. With the right upkeep, you can protect your gutters for a long time, keeping them clean, clear, and mould-free for good.
When to call in the pros to clean your gutters
There comes a point when you’ve just got to throw your hands up and hire a professional to maintain your gutters. There’s no shame in it — even the most competent, confident DIYer needs backup once in a while. DIY gutter system cleaning is great for regular maintenance, but sometimes, the job’s just too big to handle on your own. If mould has taken over large sections of your gutters, no amount of scrubbing will be enough to fix it properly. Likewise, if your gutters are already damaged — sagging, rusted, or full of cracks — it’s best to get them looked at before they cause bigger problems. And of course, if your gutters are high up or difficult to access, climbing a ladder to scrub out mould isn’t worth the risk. Safety always comes first.
