How to Get Rid of Mould on Deck: 7 Effective Ways

Mould is a pain, isn’t it? You step outside, ready to enjoy your cuppa in the sunshine, and… you’re greeted with unsightly black, green, or even white splotches ruining your pristine decking. It’s a common frustration for UK homeowners, especially as we’re more prone to rain than our other, luckier European neighbours. But no need to worry, mould doesn’t need to be a constant presence when you step out onto your deck. Yes, it might be stubborn, but it’s not unbeatable. 

So, what’s the best way to tackle it? It’s simple – regular maintenance. If you take care of your deck and follow the methods below to keep it in tip-top condition, we can pretty much guarantee that you can banish mould from your outdoor space, and keep your deck looking its best all year round. (Yes, even during the UK’s rain season – also known as most of the year).

Why Is There Mould on My Deck?

First of all, why does mould love our decks so much? It all boils down to three things: moisture, shade, and food (in the form of organic debris). Wood decking, particularly in shaded areas or spots that don’t drain well, provides the perfect breeding ground for mould to flourish.

Think of it like this: mould spores are pretty much everywhere, floating around in the air, and all they’re waiting for is a damp, welcoming surface to land on and start a family. So if there’s leaves, dirt, and even pollen settling on your deck, this provides mould spores with the nutrients they need to thrive.

You’ll often see black mould on deck wood, which can be particularly unsightly. This type of mould, while not always the most dangerous, certainly isn’t doing your deck’s appearance any favours. You may be dealing with other types of mould on wood deck surfaces as well, and oftentimes the cleaning solution is the same.

Preparation Before Cleaning: Safety First

Before you go full beast-mode on that mould, let’s talk safety. Dealing with mould, even outdoors, requires some precautions:

Gloves

Protect your skin from irritation and potential allergic reactions. Rubber gloves are your best friend here.

Mask

Mould spores can be harmful when inhaled, so if you’ve got any old COVID masks lying around, pop one on. A dust mask or respirator is also ideal.

Eye Protection

Safety goggles will shield your eyes from splashes and airborne spores.

Clothing

Wear old clothes that you don’t mind getting a bit messy (or potentially bleached, depending on your cleaning method).

Gather your cleaning supplies too. Depending on the method you choose (we’ll get to those in a minute!), you’ll likely need:

• A Stiff-Bristled Brush: Use one with stiff bristles, but avoid wire brushes as that can damage the wood.
• A Bucket: This is to hold your cleaning solution.
• A Garden Hose: A hose with a spray nozzle is ideal (or a pressure washer, used with extreme caution).
• Your Chosen Cleaning Solution: We will detail the solutions below.

7 Effective Ways to Remove mould on Deck

Right, let’s get down to business. Here are seven effective ways to tackle pesky mould on your deck, ranging from gentle DIY solutions to more heavy-duty options:

The Vinegar Power Wash

Did you know vinegar is a natural mould killer? White vinegar is a fantastic, eco-friendly option for tackling mild to moderate mould growth, and you can pick it up from your local Sainsbury’s at an affordable price. Here’s how to use it:

• Step 1: Mix a solution of equal parts white vinegar and water in your bucket.
• Step 2: Apply the solution liberally to the affected areas of your deck.
• Step 3: Let it sit for at least an hour – the longer, the better.
• Step 4: Scrub vigorously with your stiff-bristled brush.
• Step 5: Rinse thoroughly with your garden hose.

Baking Soda Boost

For more stubborn mould (for example, mould that’s been around for a while), baking soda gives you some extra scrubbing power. It’s mildly abrasive, which will help lift the mould without damaging the wood.

• Step 1: Make a paste of baking soda and water (think toothpaste consistency).
• Step 2: Apply the paste to the mouldy areas.
• Step 3: Let it sit for 15-20 minutes.
• Step 4: Scrub with your brush.
• Step 5: Rinse well.

The Soap Scrub 

Sometimes, good old-fashioned soapy water is all you need. This is best for new or light mould or as a follow-up to other methods.

• Step 1: Mix a mild dish soap (like washing-up liquid) with warm water in your bucket.
• Step 2: Apply to the deck and scrub with your brush.
• Step 3: Rinse thoroughly.

Oxygen Bleach Solution

Oxygen bleach is a more powerful cleaner than vinegar or baking soda, but it’s still gentler on the environment (and your plants!) than chlorine bleach.

• Step 1: Follow the manufacturer’s instructions for mixing the oxygen bleach powder with water.
• Step 2: Apply the solution to the deck.
• Step 3: Let it sit for the recommended time (usually 15-30 minutes).
• Step 4: Scrub and rinse.

Commercial-Grade Deck Cleaners

There are many commercial deck cleaners specifically formulated to remove mould and mildew, and these can be very effective on decks. However, it’s imperative that you always follow the instructions carefully, and look for products that are safe for use around plants and pets.

• Step 1: Always read the label and use the product according to the instructions.
• Step 2: Apply to the deck.
• Step 3: Allow to sit, as per package instructions.
• Step 4: Scrub and rinse.

Pressure Washing (with Caution!)

A pressure washer can be a quick way to blast away mould, but it must be used with extreme caution, ideally by a professional. Too much pressure can damage the wood fibres, leading to splintering and a rough surface. 

• Step 1: Use a low-pressure setting and a wide fan nozzle.
• Step 2: Keep the nozzle moving constantly, and don’t hold it too close to the deck.
• Step 3: Test a small, inconspicuous area first.

Important Note: If you have a soft wood, like cedar, you might be best to steer clear of the pressure washer for cleaning.

7. Borax

Borax, a naturally occurring mineral, and also doubles as an incredibly effective mould and mildew remover. But! It’s also incredibly toxic if ingested, so you’ll need to keep children and pets away from the area when treating your deck. Here’s what to do:

• Step 1: Add one cup of borax powder to a gallon of hot water.
• Step 2: Apply to the deck.
• Step 3: Let it sit, for at least 15 minutes.
• Step 4: Scrub and rinse.

Important Note for All Methods: Always test any cleaning solution on a small, hidden area of your deck first to ensure it doesn’t cause discoloration or damage. Protect surrounding plants and grass by covering them with plastic sheeting or wetting them down thoroughly before and after cleaning.

Which Type of Decking Is Most Mould Resistant?

If you want to be free of mould entirely, why not opt for composite decking? While composite decks can still get some surface mildew in very damp, shady conditions, they’re far more resistant to mould growth than traditional wood. This is because composite decking is non-porous, which means that mould can’t penetrate the surface – this makes it much easier to clean. It does, however, mean that maintenance looks a bit different – for some great composite deck maintenance tips, check out our guide over on our blog.

Key Takeaways

There’s no two ways about it, mould on your deck is a nuisance – but it’s important to remember that it’s a manageable one. Remember, regular maintenance is the best defense against future mould outbreaks. And if you’re tired of the constant battle, it might be time to explore low-maintenance composite decking. And at Dino Decking, we even offer free samples of our decking with next-day delivery across the UK. Ready to explore your options? Browse our variety of decking boards to find the perfect fit for your outdoor space.