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How-to Guides

How to clean render and masonry

How to clean render and masonry

How to clean render & masonry

This how-to guide explains how to clean render & masonry, this includes using softwash solutions.

Render & masonry surfaces typically suffer from green algae, red algae, black lichens, and rust marks. We have 2 main products for cleaning render & masonry, these products work in slightly different ways, they are:-


Floorseal Green Remover Concentrate. This is a slower acting ‘spray and leave’ type formula. It will break down green and red algae over days or weeks following its application.

This product can also be used as a final treatment after pressure washing or after using the Render Cleaner Softwash Solution.

Floorseal Render Cleaner Softwash Solution. This is a fast-acting solution that will break down green algae, red algae, and particularly black spot lichens & black streaking

You can click through to the individual product pages by clicking on the product titles highlighted in blue.

The products listed above work in different ways from one another. So, for this reason, they can be used for slightly different purposes.

How to clean render and masonry

1.   Floorseal Green Remover Concentrate.

Floorseal Green Remover is an easy to use ‘spray and leave’ type cleaning product. It is to be diluted 1:5 (or 1:3 in severe cases) and simply sprayed onto a dry surface.

An acid-free product, it is free from solvents & VOCs.

Simply spray on and leave the product to work, it will remove red & green algae over the following few days and weeks. It will also remove moss if sprayed onto roof tiles or walls.

We have found green algae disappears in a few days, while red algae are more resilient and may take several weeks to disappear. You may wish to repeat the treatment on red algae. Please note red algae can increase in colour after it is treated before fading.

This ‘spray and leave’ type render & masonry cleaner is safe to use on:- cement-based renders, sandstone, slate, concrete, limestone, granite, most other natural stone, clay tiles, clay bricks, and concrete.

Floorseal Green Remover Concentrate is the easiest way to treat render which has organic contaminations present. Particularly for the removal of green algae from rendered walls and roofs, it does not require rinsing and can be sprayed directly onto the surface when it is dry.

Spray the product onto the surfaces with a simple low-pressure pump-up sprayer. You should not spray this product directly onto adjacent lawns or bedding plants etc.

If you have already pressure washed your render (and it is now clean) this product can still be applied as a preventative measure. When used in this situation the solution is applied as normal and remains on the surface inhibiting the germination, and therefore return, of organic contaminations.

The coverage & dilution rate of this Green Remover Concentrate are:-

Approximately 125m2 per 5 litre container- when diluted at 1:5. One part concentrate to 5 parts water. This will create 30 litres of ready to use solution (RTU) from a 5-litre container.

Apply to the RTU at a rate of 1 litre of solution to 4-5m2 of surface area. You should achieve coverage of approximately 125m2 of surface area from a single 5 litre container of concentrate.

Do not exceed the recommended maximum coverage rate of 5m2 per litre of diluted solution.
For heavy contaminations of algae or moss dilute 1 litre of concentrate to 3 litres of water.

*Coverage rates are dependent on surface porosity, texture & level of soiling. Please conduct a test patch to assess your dwell time and coverage rate. Porous stone & concrete will require more product than fine renders.

examples of render and masonry cleaning

2.   Floorseal Render Cleaner Softwash Solution.

Floorseal Render Cleaner Softwash Solution is a more powerful cleaning solution. It should be diluted at 1:5 with clean water. It is non-acidic and free from solvents & VOCs.

This softwash solution is a more powerful & faster acting solution. It will break down green algae, red algae, and black spot lichen during the actual treatment time. In other words, you will see results within minutes not days.

Render Cleaner Softwash Solution should be sprayed onto the surface and allowed to dwell for approximately 15 minutes. Once the dwell time is complete rinse away with clean water.

It is important to use a dwell time of at least 15 minutes and keep the product wet during this time. You may need to overspray the area 2 or 3 times to keep the surface wet during the dwell time.

If you are specifically dealing with lichens, you may wish to increase the dwell time. Lichens are more likely to take hold on natural stone or renders adjacent to trees or hedges.

This product will remove red & green algae and particularly black spot lichens which do not respond to the slower acting render cleaners.

Floorseal Render Cleaner Softwash Solution is a more powerful product than Floorseal Green Remover Concentrate. So can be used on surfaces where slower acting products have failed.

Sometimes an algae has stained the render even though the contaminations on the surface have already been removed. In this situation, you may require a stronger product like Floorseal Render Cleaner Softwash Solution to totally remove the residual staining.

This can happen on very pale renders which have had a strong contamination of green algae, possibly caused by leaking gutters or condensation from central heating outlets.

The product is safe to use on:- cement-based renders, sandstone, slate, concrete, limestone, granite, most other natural stone, clay tiles, clay bricks and concrete.

Please note: The solution should not be allowed to encounter UPVC, metal frames and bare wood. If it does encounter any of these materials, please rinse them thoroughly with clean water.

Whilst this product is a little more involved to use than a ‘spray and leave’ type cleaning solution, the results can be dramatic. The main difference is the need for dwell time, keeping the product wet and rinsing after use.

The dilution and coverage rates of Render Cleaner Softwash Solution are:-

Approximately 125m2 per 5 litre container- when diluted at 1:5. One part concentrate to 5 parts water. This will create 30 litres of ready to use solution (RTU) from a 5 litre container.

Apply to the RTU at a rate of 1 litre of solution to 4-5m2 of surface area. You should achieve coverage of approximately 125m2 of surface area from a single 5 litre container of concentrate.

Do not exceed the recommended maximum coverage rate of 5m2 per litre of diluted solution.

This product can be used up to and including neat on stubborn black spot lichen.

*Coverage rates are dependent on surface porosity, texture & level of soiling. Please conduct a test patch to assess your dwell time and coverage rate. Porous stone & concrete will require more product than fine renders.

How to remove rust on render

Please use our non-acidic rust remover called Floorseal Rust Remover For Stone. This product is safe to use on acid-sensitive materials. Acid sensitive surfaces are materials like cement-based renders, limestones, and concretes.

You should always test rust removers before committing to the whole area. Coloured concretes can react even with a non-acidic cleaner so it is always wise to check first!

Rust Remover For Stone should be applied and kept wet on the surface, rinse away after no more than 10 minutes. The liquid reacts and turns purple when in contact with rust.

This non-acidic rust remover can also remove long term drainage/streak marks from leaking gutters which can be dark or orange marks.

Always rinse the area thoroughly after use.

Coverage rates:-

1 litre of rust remover will cover approximately 10m2 of surface area. This rate will vary depending on the porosity of the surface being treated.

example of before and after render cleaning

In conclusion: so which is the best cleaner for cleaning render?

The answer is it depends on what you are cleaning and what sort of contamination you are dealing with. You should also take into account how easy, or difficult, it is to access the area you are cleaning.

Floorseal Green Remover Concentrate is a slower acting easy to use cleaner. Great for removing clumps of green matter, green algae and red algae. Contaminations take a few days to disappear, but the application of the cleaning solution is very easy.

Spray this product directly onto the surface and leave it to dry. You can also apply this product as a preventative measure after pressure washing the surface. It will slow the regrowth of organic contaminants. Or apply after the application of Floorseal Render Cleaner Softwash Solution for the same purposes.

Green Remover Concentrate does have a residual effect so can be used as preventative measure even after the render has been successfully cleaned. This may have been via a pressure washer or the application of Render Cleaner Softwash Solution.

Floorseal Render Cleaner Softwash Solution acts more quickly than the previous product, therefore, providing rapid results. The cleaning solution will also kill black lichens & moulds which ‘spray and leave’ type cleaners generally cannot. It is more powerful than Green Remover Concentrate so, for this reason, may be preferable.

It’s perhaps a little more involved to use as it requires dwell time & rinsing after its application. But it is worth the effort when dealing with black spot lichens, moulds & deeply ingrained organic staining.

Renders adjacent to trees & hedges are often marked more severely than open south-facing walls. A stronger solution may again be preferable in this situation. A little testing with both products will usually provide an answer.

Floorseal Rust Remover for Stone is used to remove general rust spots and stains on render & masonry. It has a non-acidic formula so it is safe to use on acid-sensitive surfaces like cement-based renders, limestone, and *concrete. It can also be used on general masonry, natural stone & clay-based materials.

*Please proceed with caution on coloured concretes by always testing the product first.

Green Remover Concentrate is available in 5 litre and 20 litre containers.

Render Cleaner Softwash Solution is available in 5 litre and 20 litre containers.

Rust Remover For Stone is available in a 1 litre container.

Free economy delivery & express shipping options are available.

Further information

Please Click Here to view all our products & accessories for cleaning and sealing render and our handy associated ‘how to’ cleaning and sealing guides.

 The information included in this article is not exhaustive. If you need further information please contact Floorseal on (01484) 861461 or email us info@floorseal.co.uk our web address is www.floorseal.co.uk.