How To Clean Stone and Concrete Lintels

Black Lichen Concrete Lintel

Have you found that your external concrete lintels or window sills have darkened over time? It doesn’t have to be that way. Read below to find out how to remove organic growth and how to clean lintels.

What Is Causing My Concrete or Stone To Darken & Become Patchy?

On closer inspection, dark growth on external concrete is usually found to be black spot lichen. Like most algae and external growth, over time it can look unsightly. Luckily, organic growth on concrete, stone and other external porous materials is relatively easy to remove.

Below we will guide you into the processes involved to get your concrete lintels and other substrates back to a fresh, clean state.

Prepare Your Problem Area

Firstly, inspect the area that needs treating. Use a power washer and a stiff broom to remove any loose sediment. Afterwards, inspect the material for any damages. We suggest to follow the below process to remove the black spot / organic growth prior to repairing the substrate. This is so the porous substrate is as ready to accept the repair as possible.

How To Clean Stone Lintels

Centrecoat R04 BG Hard Landscape Cleaner is ideal for removing both the lichen and any other residual dirt. This cleaner is also suitable for exterior porous hard ground surfaces such as natural stone, cement, tarmac, brick, terracotta etc. Therefore it is ideal for cleaning organic microbiological growth from many areas. This includes driveways, pathways, patios, decking and exterior steps. It is even suitable for the cleaning of platforms, forecourts, porous external furniture such as stone benches or even tennis courts.

This product may need 2-3 hours dwell time for the product to work effectively. Therefore it is important to select a day where no rain is expected and temperatures are not too hot or cold.

Find out more about the best weather to do external decoration view our blog here:
What Are The Ideal Weather Conditions For Painting?

Apply The Centrecoat Hard Landscape Cleaner

Firstly, in a hidden area, apply a small amount of the product to discover the optimum time to allow the product to work. After some time, douse the area in water and see if the product has worked. If it hasn’t fully worked, try leaving the product on for slightly longer.

Once you have an idea of how long the Centrecoat R04 BG Hard Landscape Cleaner takes to work, coat the area with the organic growth remover using a brush or low pressure spray. If the substrate and weather conditions are a bit on the hot side, you can cover the wet area with a plastic sheet to prevent the product drying out.

Once the allocated working time has passed, thoroughly rinse the area with water. Use a broom to easily wash off and neutralize the surface.

To brighten areas such as paths and patios leave longer before rinsing – ie up to 8 hours.

Has Treatment Not Fully Removed All The Visible Organic Growth?

For heavily contaminated areas, afterwards you can treat the substrate with Centrecoat R05 BF Facade Cleaner. This product is supplied ready to use. Apply neat to a dry or damp surface with a brush, roller or sprayer. Soak the area with a generous, even application. Leave for 20 – 90 minutes, then rinse with water and allow to dry.

Ideally afterwards protect the cleaned surface with a suitable anti fungal agent to limit regrowth.

Prevent Organic Growth From Happening Again

Once all surfaces have been suitably cleaned we advise to protect the surface to prevent the organic growth returning. For this, we recommend using Centrecoat All Purpose Protector.


Remember to follow advice and guidance on the Product Data Sheets prior to use.

If in doubt about how to clean your lintels or any other difficult organic growth, contact our technical team for in depth professional advice. The technical team are available weekdays between 8.30am to 5.00pm on 01462 421333.

Was this article helpful?

Related Articles