How To Remove Black Mould From Concrete

A property that is well kept can appear dirty and ignored because of black mould. Whether that's on your concrete driveways, paths, or other outdoor areas used for entertaining, it can cause slippery and unhealthy conditions, especially when the concrete remains damp. At Wright Pressure, we frequently handle persistent organic growth and the accumulation of grime and mould on exterior concrete all over Melbourne.

The secret to getting a good outcome is to understand what you are cleaning and to select the correct mix of chemical treatment and pressure.

Why does black mould grow on concrete?

Since concrete is porous, it has small pores in which moisture can be held and in which dirt and organic matter can accumulate. Black and green growth tends to occur in shaded areas, at the edges of gardens and in places that get little sunlight, particularly if damp conditions continue.

It's also important to remember that not all black stains are necessarily mould; tyre marks, oil stains and other embedded contaminants can appear similar and will need a different kind of cleaning treatment.

Does pressure washing eliminate black mould?

Pressure washing is very effective at getting rid of surface dirt and at lifting the visible organic growth from concrete, but simply using pressure isn't enough to get rid of all the biological growth that causes mould to come back. This is the reason why it may be possible to achieve a satisfactory first result by just blasting the driveway with water and seeing those black mould spots disappear without tackling the fundamental issue.

When deciding on the most appropriate cleaning method at Wright Pressure, we take into account both the visible contamination and the state of the concrete. A proper treatment combined with professional pressure cleaning will yield a more effective and longer-lasting result than using water pressure alone. Using only high pressure can lead to that mould starting to return within a matter of months.

How to Remove Black Mould from Concrete

Follow the following steps to have a high chance of successfully removing black mould from concrete.

Preparing the area

Make sure to remove any loose leaves, dirt or debris from the surface so that the chemical pre-treatment can fully focus on killing the mould only.

Make use of suitable protective equipment, guard nearby plants, and avoid chemical runoff flowing into stormwater drains. It is necessary never to mix bleach-containing products with other cleaning chemicals, as this can create a toxic chemical reaction.

Chemical pre-treatment

Apply a chemical treatment that is appropriate for use on external concrete and adhere to the manufacturer's instructions regarding dilution, application and the required contact time; certain treatments assist in breaking down or killing organic growth, which makes it easier to remove when rinsing.

At Wright Pressure, we recommend using sodium hypochlorite (aka Bleach/pool chlorine) applied at a 1:1 ratio of bleach to water to the surface mould and let it sit for 10-15 minutes. It's important to make sure that the chemical does not dry on the surface, so misting it every 5 minutes with a light application of the chemical mix can be useful.

Carefully pressure wash the concrete

When the treatment has been applied, rinse and clean the surface using the appropriate pressure and method. A 15-degree pressure nozzle at 3000 psi is more than enough to successfully remove the mould from concrete.

Be aware that if too much pressure is used or if the concentrated spray is held too close, it may etch or damage the concrete, so it is necessary to modify the method to match the surface.

When you have allowed the concrete to dry, check the result, as sometimes when surfaces are wet it can be hard to tell if you've achieved the full result.

If certain dark stains stay behind, it might be necessary to hire the professionals at Wright Pressure to inspect and determine any other method that might be required. This could include us using hot water pressure cleaning systems, which can make a huge difference as weve seen many times for removing black mould from concrete.

How can you help to prevent mould from coming back?

Even though no cleaning method can ensure that mould will never come back, you can decrease the conditions that lead to its regrowth by keeping concrete free from leaves and organic debris, improving drainage as far as is possible and reducing persistent moisture or excessive shade when you can.

A concrete sealer that is appropriate can contribute to reducing moisture penetration, with the effect depending on the type of surface and product used. Yet it is necessary to clean the concrete properly and ensure that it is sufficiently dry before sealing it.

Professional Concrete Cleaning in Melbourne

We at Wright Pressure know that getting a good result is not just about spraying water over a driveway; our method makes use of professional hot water pressure cleaning equipment, the right cleaning chemical treatments and the proper technique for the type of surface being cleaned.

Our services for driveway and concrete cleaning help to remove accumulated grime, mould and organic growth from external surfaces. We look at each job on its own merits and strive to obtain the best possible result without damaging the condition of your concrete.

Should black mould be covering your driveway, concrete or the outdoor paths, get in touch with Wright Pressure for professional pressure washing services in Melbourne and ask for a quote that is specific to your property.

Get Quote Here