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How to Clean Modern Render. - What Type of Render do you Have?

What is render?

Render is an excellent choice for the external finish of both commercial and domestic properties. Simple to apply, easy to maintain and affordable, render gives the building a crucial waterproof layer and a smart, attractive aesthetic. Property owners need to keep it free from algae, fungi and staining to keep render looking good.

Properly maintaining your modern render will ensure your building is protected from the elements, and its exterior looks good for as long as possible. By continuing to read this blog post, you can learn more.

What type of render?

Before you clean the render on your property's exterior, you need to find out exactly what type of render it is. Many modern renders are now on the market. Most are mixed with polymers to improve their protective qualities.

Different renders need different treatments and various tools. Some renders can withstand power washing, while others are too delicate to survive the process. If you are unsure what type of surface your property has, talk to the manufacturer or call Spectrum’s specialist cleaning team.

 Jet washing

Most companies that manufacture modern render, including Weber Saint Gobain and K-rend, recommend using a power or jet wash to remove stains and algae growth. Power washing will clear the surface of the render of light discolouration caused by weathering, metalwork and algae. As long as the staining is not too ingrained, a thorough power wash should restore the building to its former glory,

However, jet washing and power washing aren’t suitable for all types of render. While some modern renders are very resilient, others, like those produced by manufacturer Sto, are more delicate and can easily be damaged or eroded by a powerful water jet. If you’re unsure whether your building is suitable for this type of cleaning, speak to the manufacturer or talk to a professional render maintenance company.

Read our blog on jet washing render here.


To get the best results from your render clean, you will need to use a little detergent. The detergent helps lift algae and other blemishes from the surface to leave it looking like new. In many cases, small discolouration areas can be removed using just detergent and a sponge or brush.

However, more stubborn stains, and properties with more extensive discolouration, will need to be cleaned using jet washing and professional tools and equipment. Again, a specialist company like Spectrum will be able to offer you advice on which detergents are most suitable for the job.


 A lot of the time, discolouration and staining on rendered buildings are caused by fungus growth. Fungi can build up on buildings exposed to the elements and often grow beneath balconies, rooflines and close to windows. As well as discolouring the exterior of a property, fungi can damage the render itself if not cleaned regularly.

Over time, this could cause you serious issues and lead to the building’s exterior needing to be re-rendered. Regularly applying fungicide not only works to remove existing fungi growth, but it also helps to prevent fungi from re-growing in the future. This is especially true when the fungicide is applied after the property has been power or jet-washed.


As well as fungi, your building’s exterior will have to contend with algae growth. Like fungi, algae grow on surfaces exposed to the elements, and, like fungi, algae can seriously damage the render overtime. Applying biocide during and after the cleaning process will kill existing algae and minimise regrowth. Biocide should be applied to the property at least once a year to prevent algae growth.  


Where a patch of render is severely discoloured or damaged, you can choose to re-cover the surface. As manufacturer Wetherby suggests, removing the damaged render and re-applying modern render can be a good option. However, as you are unlikely to achieve a finish that exactly matches the rest of the property, this should only be done when you can re-render an entire panel or when cleaning is not an option.

 P.A.S.T. cleaning technology

 Our patented rend-care system will help you maintain your building and keep it looking as good as possible. Spectrum has developed the most comprehensive and useful system for cleaning modern render. Our patented P.A.S.T. process brings together many of these cleaning techniques to leave your property looking like new.

The first part of the process is planning and preparation. During this stage, we will assess your property, closely examine the render and look at access. Once we have thoroughly surveyed the site, we will decide which cleaning methods and processes will give us the best results.

To clean a property effectively and thoroughly, we then 3D print our tools to ensure they are perfectly suited to the job. During this part of the process, we will also create a plan outlining any additional challenges at the site and detailing exactly how we will complete the project.

The next stage involves the application of biocide. The biocide treatment will kill any algae growing on the surface of the building. Algae can discolour and damage modern render, so as we must remove as many algae as possible.

The biocide treatment we use is incredibly effective at killing algae and removing residue. This helps us to achieve great results from our cleaning process.

Once we have applied the biocide, we use steam to remove stains, residue and discolouration. The steam is heated to 150 degrees to make it as useful as possible. If any staining remains following the steam clean, we use a specialist treatment to remove the discolouration and leave the building looking new.

Our patented rend-care system will help you maintain your building and keep it looking as good as possible. To help you learn everything there is to know about cleaning and maintaining modern render. We are running a series of free CPD seminars to go through the most cost-effective and time-efficient ways of maintaining modern render.

If you are interested in attending a seminar, or if you’d like to learn more about the services we offer, contact us here.

How to Clean Modern Render. 1How to Clean Modern Render. 2How to Clean Modern Render. 3How to Clean Modern Render. 4How to Clean Modern Render. 5
Back to Blog Posts

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Can We Help With Your Specialist Building Cleaning and Restoration Needs?

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