Concrete is a popular choice for outdoor areas like patios, pathways, driveways, and pool surrounds. It’s durable, low-maintenance, and looks great. But one of the biggest frustrations for homeowners is moss and mould growth, especially in shaded areas that are frequently wet. These unwanted visitors aren’t just ugly, they can make surfaces dangerously slippery and weaken concrete over time. In this post, we’ll explain why moss and mould thrive on concrete, how to prevent them from growing on your outdoor concrete surfaces, and what you can do if they’ve already taken over.
Do Moss and Mould Grow on Concrete?
Concrete is a porous material meaning it naturally absorbs moisture. When combined with debris like leaves, dirt, and dust, it creates the perfect breeding ground for moss and mould. This is especially true in any areas that stay damp for long periods of time.
Geelong’s coastal climate makes this issue even worse. With the regular rain, moisture lingers particularly in shaded areas where the sun’s UV rays can’t reach. If your concrete stays damp for too long, you’ll notice black mould stains or green, fuzzy patches developing.
Why It’s Important to Keep Moss and Mould Away
Ignoring moss and mould can lead to several issues:
- Safety hazard. Moss and mould make surfaces extremely slippery, increasing the risk of falls—especially around pools or frequently used outdoor areas. While slip resistance standards aren’t mandatory, the Australian Building Codes Board (ABCB) provides guidance on best practices to reduce slip hazards on concrete and other outdoor surfaces.
- Looks Dirty. Dark mould stains and green moss patches make your outdoor areas look unkempt and neglected.
- Long-term concrete damage. Over time, moss and mould can eat away the concrete surface, causing stains, cracks, and erosion.
How to Prevent Moss and Mould Growth on Concrete
1. Clean Regularly
Regular cleaning is the simplest and most effective way to stop the growth of moss and mould. A quick sweep every week helps remove dirt, leaves, and debris that trap moisture and encourage mould growth. Hosing down your concrete monthly washes away spores before they can settle, reducing the chance of an outbreak.
For a deeper clean, using a pressure washer every few months will blast away any build-up and keep your concrete surface looking fresh. Staying on top of cleaning makes a significant difference in preventing moss and mould from gaining a foothold.
2. Improve Drainage
If water pools on your concrete after rain, it creates the perfect condition for moss and mould to thrive. Identifying and addressing low spots where water collects helps prevent long-term moisture retention. If you notice persistent puddles, consider adjusting the slope of your concrete or installing drainage solutions like French drains or additional drainage channels. Keeping your gutters and downpipes clear also helps by directing excess water away from your concrete, reducing the likelihood of damp spots forming.
3. Let the Sun Shine In
Moss and moulds love shaded, damp environments so increasing sun exposure can significantly reduce their growth. Trim back overhanging branches or large shrubs to allow more sunlight to reach your concrete, helping it dry out faster after rain.
If you have outdoor furniture that shades certain spots, try rearranging them periodically to ensure that all areas get some sun exposure. The more sunlight your concrete receives, the less hospitable it becomes for moss and mould.
4. Apply a Moss and Mould Inhibitor
In areas where moss and mould are persistent problems, applying a preventative treatment can help keep them at bay. There are various concrete-safe inhibitors available that create a protective barrier against moisture and spore growth. These treatments work best when applied after a thorough cleaning so that they adhere properly to the surface. If your concrete is prone to moss and mould growth, using an inhibitor regularly makes a noticeable difference in preventing growth.
5. Seal Your Concrete
Sealing your concrete is one of the best long-term solutions for preventing moss and mould. A high-quality sealer reduces the material’s natural porosity, making it harder for moisture to soak in. There are different types of sealers available including penetrating and film-forming options, each providing a protective layer to repel water. Applying a fresh coat of sealer every 2-3 years ensures maximum protection. If you’re looking for more ways to enhance safety, especially on outdoor surfaces, check out these slip-resistant techniques to make your concrete safer.
What to Do if Moss or Mould is Already Growing on Your Concrete
If moss and mould have already taken hold of your outdoor concrete surfaces, here’s how to remove them effectively:
Pressure Wash the Surface
The first step in removing moss and mould is to use a high-pressure cleaner. A pressure washer can remove most of the growth without requiring harsh chemicals. Be sure to use the right pressure setting to avoid damaging the concrete while still effectively clearing away the buildup.
Use a Cleaning Solution
For stubborn patches that won’t come off with pressure washing, using a specialised cleaner makes the job easier. A product like 30 Seconds Outdoor Cleaner is designed for surfaces like concrete, pavers, and brick, breaking down moss and mould without the need for heavy scrubbing. Simply apply, wait for it to work, and rinse it off for a refreshed surface.
Scrub the Affected Areas
Using a stiff-bristled brush, scrub the affected areas to remove any remaining moss or mould. Pay close to textured surfaces since the growth might be more deeply embedded. This will ensure that all spores are removed, preventing quick regrowth.
Rinse and Allow to Dry
After scrubbing, rinse the area thoroughly with clean water to wash away any remaining cleaning solution. Allow the surface to dry completely as lingering moisture can encourage moss and mould to return quickly.
Apply a Preventative Treatment
Once the concrete is clean and dry, applying a moss and mould inhibitor or sealer will help prevent regrowth. These treatments create a protective barrier that reduces moisture absorption, making it harder for moss and mould to establish themselves again.
Keep Your Concrete Clean and Safe
Moss and mould are an eyesore and they create safety hazards that can lead to long-term damage. Fortunately, with regular cleaning, good drainage, and preventative treatments, you can keep your outdoor surfaces looking great and free from slippery growth. If moss and mould have already taken over, a thorough cleaning followed by sealing will help prevent regrowth. Regular maintenance is key to keeping your concrete in top shape. For more tips on protecting and prolonging the life of your concrete, check out these concrete maintenance strategies.
If moss or mould has caused cracks or damage to your concrete, a professional concrete repair service can restore its strength and appearance. Addressing these issues early prevents further deterioration and keeps your outdoor surfaces safe and durable. Interested in our concrete services in Geelong? Send us a message and see how we can bring your outdoor surfaces back to life!
