Why It’s Important to Clean Render

Why It’s Important to Clean Render

Render can instantly transform the look of a structure, offering a modern, clean and attractive finish to any building. As well as improving the building’s aesthetics, it can also protect the underlying walling material from the effects of weathering and rainwater penetration. When render is properly maintained this protection can last up to 30 years.

Modern render materials and manufacturing have changed significantly since the days of lime render, commonly found on 18th-century properties and the universal battleship grey pebble dashing of the post-war era.

Whilst render can benefit your building both visually and structurally, it can be susceptible to staining. The organic growth of algae, moss and lichen in addition to general dirt and grime can discolour your render. Nearby trees can turn a nice coloured render into a real red and green mess with lichen and other organic growth.

Additionally, tide marks of black will appear under window sills or any other protrusions on your walls where moisture can gather and drip. Any leaks in a gutter joint can turn the render below it into an unsightly green or black mess, which nobody wants to see. Add to this atmospheric staining if you’re near a busy road and throw in a few unsanitary birds nesting nearby, and your pristine wall covering can soon lose its original cleanliness and lustre.

By taking a small amount of time to clean your render, you can soon have your render looking brand new, and you can be proud that your property looks well maintained and cared for. There is something special about coming home or going into work, knowing that your property looks the best in comparison to the rest of the street. This personal pride can have an additional positive effect on the surrounding area as well, soon everybody will want their property to look as good as yours and before long the whole area could be improved.

Leaving this staining untreated even longer can actually damage the render. If moss, lichen and algae are allowed to grow on the surface this can prematurely “rot” the minerals in the render. If left to freeze and expand, this can potentially blow the surface off the render, which in turn can then be a breeding space for more moss, and so the cycle begins again.

Cleaning your render regularly is crucial, and there are numerous methods and substances available to help you with this maintenance. At the end of this article, you should know exactly why and more importantly how to maintain your render and to keep it looking as good as the first day it was applied!


Within this article, we’ll cover:

Why it’s Important to Clean Render

It is a common misconception that some renders are “maintenance free”. Although modern renders are extremely tough and incredibly hard-wearing, under normal circumstances they should last at least 30 years. Even with this durability, they will all benefit from some light maintenance throughout their lifetime.

It is important to remember that your property is highly likely to be the most expensive thing that you have or will ever purchase. Such a huge asset needs to be looked after as best you can to retain its value. By regularly cleaning your render, you are investing in your property.

There are several reasons why you should be cleaning your render. One of the most important is to maintain the aesthetic qualities of a well-rendered property.


Research has shown that a colossal 93% of people say they are more likely to attend a viewing if the exterior of the property is well maintained (Dulux 2020). It is true that the phenomenon of good ‘kerb appeal’ makes your property much more attractive. Cleaning your render to remove dirt and stains will immediately freshen up your property and add lots of value to it, at little expense. If you spend a little bit of time getting your render cleaned, it can sometimes be as good as getting your property completely repainted, at just a fraction of the cost.

Source: https://www.dulux.co.uk/en/articles/boost-your-kerb-appeal-weathershield

When we mention ‘kerb appeal’ what do we mean? ‘Kerb appeal’ is a term used to describe how attractive and appealing your property is to a potential buyer. Although you may not even be considering selling your property at the moment, this should still be taken into account as this is how people will judge your property. The phrase “first impressions count” is highly appropriate when it comes to property, and the overall condition of the exterior of your building is a key component of this.

Imagine that you are looking for a new home. What is the first picture that you see, is it the internal decoration or the carpets, the kitchen or the bathroom suite? No, the first picture you see is of the front exterior of your property. If this looks dirty, neglected, and uncared for, then people will not care what the interior looks like as they will not progress past that vitally important first impression.

A well maintained and clean property reflects directly on the owner, it is normal to take pride in your property and by ensuring that your building maintenance includes the cleaning of your render, the look of your property will drastically be enhanced. There is no doubt, having a well looked after house gives you that extra bit of the feelgood factor.

An added potential bonus is that your neighbours may well view your property and become motivated by your efforts into sprucing up their own. We all know there is a definite element of ‘keeping up with the Joneses’, and this can benefit the overall look of the immediate vicinity once people start following your actions. Ultimately, this can only add to the value and desirability of your area, and therefore increase your property’s value further.

Structural Integrity

Additionally, regular cleaning is important to prevent or minimize the likelihood of structural damage. Render cleaning can be seen as a preventative measure as well as a cure as in some cases you may not be able to see the damage until it is too late. Potentially, this can cause catastrophic damage to the integrity of the render, which can result in devastating structural damage.

If hairline cracks are allowed to develop, they will allow frost to penetrate and water to soak in, which over time will freeze and expand. Over time, this can result in a catastrophic failure of your wall covering. This is referred to as ‘blowing’ the render which causes the external coating to become loose and this will expose your underlying structure.

Once this underlying structure is exposed to damp then you are exposing your property to the potentially huge risk of the dampness reaching the timber frames of your building. With areas of the internal structure exposed, any moisture, dirt or even animals can damage your property. When this happens and the damage is caused to the underlying structure, it can require an extremely costly procedure to repair this.

The thought of dampness running throughout your property fills you with dread and fear as it should, but the risk of this can easily be reduced by keeping your render clean and algae free. The best methods for achieving this can be found further on in this article.

The potential costs of having to replace your rendering alone are extremely high, and any temporary patching will not give you the finish that you are looking for and may detract from the overall appearance of your property. It is vital that you give your render the TLC that it requires to keep it fully operational, as well as keeping your property looking aesthetically pleasing.

If you are considering patching your render, then this depends on the type of rendering that you have, as detailed in the sections below. If you have silicone or acrylic patching then patch repairs are definitely not advised as you would need to replace the entire wall to ensure a consistent colour is achieved. For cement rendering, you may be able to chisel off the old damaged section, replace this as required and apply a fresh coat of paint.

A general rule of thumb that is used when deciding whether to patch cement render is that if the patch is required as a result of a specific event that has caused the damage, such as a water leak or some kind of impact damage that has affected the structural integrity, then it may be possible to fashion a repair.

Unfortunately, if this is likely to be the first of many incidents as the render is generally in a very poor condition due to age or severe organic growth, then it almost becomes a ‘false economy’ to keep making smaller repairs. In these circumstances, it is sometimes better to bite the bullet and go for a complete replacement.

To replace your rendering, you will need to have the existing rendering removed and disposed of, as well as scaffolding costs and a few other potential pitfalls that you may or may not be aware of. For instance, not only is this unlikely to be covered by your house insurance your house insulation may also need to be brought up to current requirements which could also incur additional costs.

Scaffolding costs can vary significantly according to many factors. Costs are calculated based on the height they’ll need to work at and the location where your property is. If the scaffolding is required to be erected on public roads and footpaths, this is more expensive than on private land. Additionally, if any obstacles such as conservatories and extensions need bridging, this will add to the final price.

Insulation costs also have several factors affecting cost. If you intend to replace or install render to over 50% of your house, then current building regulations state that you must meet current wall insulation requirements. For a cavity wall, this can be filled at extra cost but if you have a single skin wall then you will need to have an insulation board installed between the render and the wall.

Cavity wall insulation is easy to install and fairly cheap but the insulation backed render can cost up to £110 per square meter for the render, boards and all associated beads and trim (JobPrices).

The additional expense of adding the extra insulation board is because this will make the wall approximately 10 cm thicker so all of the existing windowsills and doorframes will need to be extended to accommodate this extra thickness.

Source: https://job-prices.co.uk/wall-rendering/

Dependent on your location and the size of your property, for traditional cement render this could cost up to £7,800 and take up to 2 weeks (Household Quotes). A small bungalow or single-storey property would be slightly cheaper as you would not have the additional scaffolding costs, but you can still expect to pay in the region of £3,000.

If you are replacing acrylic, silicone or lime render then there may also be some additional costs to take into account.

Whilst this is not the ideal outcome, this can be the best option for your property. However, this can all be avoided through proper maintenance and cleaning. By taking the time to regularly inspect your render, and to clean off any organic growths before they get too large, you will save yourself the time, money and hassle required to replace your entire rendering.

Given these prices, the relatively minimal outlay in both time and expense for a regular maintenance routine could represent a significant saving as well as keeping your property looking pristine and well cared for. So, take a look through the notes below and see what you can do to keep your render as good as the day it was applied and how you can keep your money in your pocket!

Source: https://householdquotes.co.uk/how-much-does-rendering-cost/

What Causes Staining of Render

As mentioned in the introduction, staining can be caused by either organic or atmospheric factors.

Organic Staining

Rendered buildings in the UK are prone to the growth of mould, moss, and algae. The reason behind this is quite simple. The UK provides the perfect, damp climate that moss and algae thrive on. Render is typically a porous material, meaning that spores can penetrate deep within the walls, and grow outwards. An outcome that is far from ideal.

Algae is one of the most common eyesores to tackle during render cleaning, as it is a microbe which can grow in tough conditions yet produces a brightly coloured eyesore. As well as ruining the aesthetic appearance of our homes and commercial properties, algae can grow within the pores of brickwork, leading to structural weaknesses which can become dangerous if left unattended for too long.

As well as algae and moss, fungi can typically be found on render. The most common species release acids and pigments which corrode and discolour render and brickwork. They can reproduce in harsh environments and will multiply exceedingly quickly, even on very acidic and dehydrated render surfaces. This can rapidly lead to a less than pleasing building exterior, affecting our pride in a residential setting, or our appearance of professionalism in the workplace.

This damp, dark environment on which moss, lichen and algae thrive is primarily found on the darker north and east sides of a building, so the worst organic growth on render will tend to be visible on these aspects. Organic growth can occur in many shapes, sizes and colours, but is most commonly seen as a green hue across large sections of render however there are often several key geographical, environmental and maintenance factors that will increase the likelihood of growth.

Geographic variations can be found when the property is near water, such as rivers, lakes and seas as these tend to have a greater build-up of organic growth. Buildings next to large trees and foliage will be more prone to organic growth as spores can transfer easily from the trees, resulting in a red and green unsightly mass of lichen and algae.

Plants, trees and climbing plants can be a visual delight, but these can cause staining to light-coloured renders and could increase the amount of render maintenance required. When you are gardening, make sure that you consider this to save yourself a job.

Gutters can often be one of the largest staining factors for render. When gutters are poorly maintained, dirt, debris and moss are allowed to build up. This can then lead to drips and leaks which spreads dirty water down your render.

This can also lead to increased moisture on the façade and subsequent organic growth. Often, gutters fixtures will rust leading to unsightly red-orange stripes down your building. By cleaning your gutters out regularly, you will be able to avoid additional tainting and staining to your render as a result.

In addition to organic growth, birds roosting on the building may have very serious consequences on the building façade, and if droppings are not removed quickly the acidic nature starts to cause more irreversible damage.

Atmospheric Staining

Rendered buildings that are situated close to roads and located in busy towns and cities are often more prone to developing general dirt and grime build-up on the surface. Although the development over time may not be as noticeable as organic growth, the cladding/render will begin to look faded and take on a dull grey appearance, particularly on lighter

cladding colours.

What Are the Different Types of Render?

Render comes in many forms, ranging from the more traditional lime renders much favoured by those renovating and extending period houses to cement, acrylic and polymer renders. These are expanded on below to help give you a better understanding of the type of render that you are dealing with and what the best methods are to keep these clean.

Cement Render

Cement render is the standard or traditional render used on external walls. This includes the older pebble-dashed finishes so popular in post-war housing. Cement render is usually mixed on-site before being applied in two or three coats. The base coats, also known as scratch coats, are scored when they are still wet. This is to give a ‘key’ for the next layer. The topcoat is then applied as a thinner layer and given a shiny finish, ready for painting.

Generally, the differences between cement and lime renders can be seen by the overall finish and effect, cement render tends to have sharper edges, corners and details and is more common in houses built in the last 100 years. It is sometimes possible to differentiate cement and lime renders by the way that the surface weathers; a cement render tends to fail in patches whereas lime render tends to erode gradually in a more uniform and even manner.

Cement render tends to be cheaper in terms of materials, but a little more expensive on labour due to the numerous coats required. It also tends to crack if the underlying structure should move. Cement renders also require regular repainting if they are to continue to look good.

Silicon/Polymer Render

Polymer render is usually sold pre-mixed in bags and has either white cement or lime as a base. These renders have polymers and other plastic-based products added to them to make the render more flexible and less prone to cracking. These are available in a variety of colours and are often through-coloured, this removes the need for future repainting.

Acrylic Render

Acrylic renders are most often applied as a thin finish coat to seal and enhance the appearance of the underlying coat. These can also add colour and texture. Additional fibres are added to prevent cracking and give a durable, lasting finish.

Silicone can also be used, promising more durability and the capacity to be self-cleaning. some claim that when it rains, the silicone will allow rainwater to wash away any dirt. These claims can be taken with a healthy pinch of salt, however, and this will still benefit from care and maintenance like any other type of render.

Lime/Mineral Render

Lime plastering was the traditional method for house rendering in the United Kingdom and fairly recently there has been a re-emergence of interest as people renovate and extend traditional older houses.

Lime render is the best option for very old houses as these require a breathable finish which is essential for the house to function as it was originally intended. Failure to do this will result in moisture getting trapped within the wall.

How to Clean Render

Dependent on the type of render that you have there are numerous ways to restore your property to its original pristine condition, we will explore some of these options now.

Whilst you are cleaning your render, it is good practice to also undertake a visual health check and check for cracks. Any cracks that are wider than the width of a credit card should be investigated further and repaired by a professional tradesman. Pay special attention around windows and doors as cracks often appear in these areas.

Numerous companies offer this service and although they have access to many chemicals and treatments as well as specialist machinery, this is also a job that you can do yourself. There are a few basic steps that need to be undertaken, most of them are obvious but it never hurts to reiterate some of them, if only one person finds these worthwhile then it is worth adding them here!

  • Try and schedule your cleaning when the weather is pleasant. You certainly don’t want to be up a ladder or soaking wet when there is any danger of ice forming.
  • Ensure that all doors and windows are closed, and all pets and children are a safe distance away from your work area and remain so for the duration of your cleaning.
  • Remember that all of the water you are using to clean your exteriors has to go somewhere so ensure that the drainage route is clear and all drains are unblocked.
  • Unless the temperature is very warm then ensure that you have adequate wet weather protection and eye protection.
  • If working at height be extremely careful, whether this is on a scaffold tower, cherry picker or up a stepladder, respect working at height at all times.
  • If using a pressure washer then try a small area at ground level first, ensure that the kick of the pressure washer does not upset your balance.

Most importantly, once you have everything in place above, ensure that you start at the very top of the wall rather than watch the mucky water drip down from the top on to the pristine lower levels!

Cleaning Cement Render

Any external organic growth on the surface will make your beautifully rendered home start to look grubby, discoloured and uncared for. In the first instance gently remove any ivy, moss or other greenery using a soft dry brush.

Dependent on the type of growth and staining you may discover that just wetting the area and brushing the affected surface will result in the removal of the vast majority or even all of the growth. However, if further cleaning is required then the next steps need to be taken.

If you are looking to remove stains from your render, or if it’s just looking a bit grubby and you have discovered that a quick brush as above hasn’t worked, then give the building a good wash using a low powered pressure washer and a mild detergent. If you don’t have access to a pressure washer then a handheld vacuum pump sprayer is an excellent tool to apply any cleaners or algaecide and can be picked up very cheaply at any garden centre or DIY store.

Always ensure that you take care to adjust the pressure washer to a fan action rather than a jet action, as the latter could significantly damage the render.

Although a high-powered pressure wash will bring good results, there is a very real and severe risk of doing irreversible damage. Too much pressure combined with the jet setting will etch invisible lines in the render creating a perfect environment for future organic growth. As the algae regrows on the surface, this hidden etching will become more prominent. This means not only will the render be damaged, but the render will look patchy and begin to show the lines of the etches as the colour of the algae deepens in these areas.

At this stage, if there is no further visible growth it may be beneficial to apply a proprietary moss and algae killer. This needs to be applied to a dry surface and has been specifically created to kill any remaining growth and the invisible spores but is then designed to be left upon the surface where it can inhibit regrowth. As with all chemicals please ensure that you follow the manufacturers’ instructions carefully.

Once this has been applied then the longevity of protection varies according to location and aspect. If the treated wall is surrounded by trees and/or constantly in shade then you may see fresh growth within 10 – 18 months. If, however, this has been applied on an open wall that is in direct sunlight most of the time, then there may be no re-growth for many years.

If there is significant and hard lichen growth then it is time to get serious and bring out the heavy stuff. You will need to purchase a more intensive/rapid moss and algae killer. This spray will kill the moss and algae growth on contact and should be left on the surface for between 30-60 minutes according to the manufacturers’ instructions.

Once the chemicals have done their work, the area should be washed with either a hosepipe and brush or ideally a small pressure washer, again ensuring that this is set to the fan setting rather than the structurally damaging jet setting. The pressure washer not only rinses the product but also removes the dead growth from the surface. Once this has been thoroughly rinsed off and left to dry, it would be beneficial to apply the long-term growth inhibitor as described above.

Under normal circumstances, this is the only maintenance that you should need to undertake to keep your cement render looking as good as the day it was applied.

Cleaning Silicone/Polymer Render

Silicone/Polymer render has a very interesting property and is what is referred to as hydrophobic. Taken literally, this translates to the ‘fear of water’. In reality, it means that the surface repels water molecules. For this reason, it requires less maintenance than the traditional rendering and it’s best just to clean as and when needed as this should not show as much dirt.

In most situations, any general dirtiness can be cleaned with either soapy water and a sponge or with a low-pressure jet wash, as mentioned in the section on cement render always ensure that this is set to the fan setting rather than a damaging jet. These surfaces should not be cleaned with any acidic cleaners as these could significantly, and irreparably damage the render.

If, however, a more significant refurbishment is required then it is possible to overpaint the render with appropriate silicone paint. This can be applied after the surface has been washed as above and then left to dry. The application of this silicone paint should reinforce the water-repelling (hydrophobic) properties of the render and also extend its lifetime.

Cleaning Acrylic Render

Acrylic render does not have the same water repellent properties as a silicone-based render, so over time both damp and mould could appear on the render. If you live in a particularly wet environment, which unfortunately the majority of us do, then this issue may well be exacerbated.

If the discolouration is only light then this surface can be cleaned with a stiff-bristled brush, a bucket of warm water and household detergent. Alternatively, a low-pressure jet wash can be used, set to the less damaging fan setting.

If the staining is really bad however then it is often a better option to repainting the façade with appropriate silicone paint.

Cleaning Lime/Mineral Render

Due to the unique nature of lime/mineral render, there are slightly different issues around its aftercare and maintenance.

Your mineral render should have had a silicone paint applied after the initial application; this is done to prevent Lime Bloom. This works by sealing the render against the elements, preventing Lime Bloom by allowing water to run off the surface layer of the render and reinforces this protective layer.

Lime Bloom is horrible to get rid of although there are many render cleaners available which are specifically designed to treat this. Usually, any patchiness or discolouration in a fully cured render in indicative of Lime Bloom.

If your render is not painted over (within the appropriate time and conditions window) then your mineral render finish will be highly susceptible to Lime Bloom which is a pain to get rid of. Despite this, there are various render cleaners on the market aimed at getting rid of it. Any signs of discolouration or patchiness in a fully cured render is generally an indicator that it has been affected by Lime Bloom.

Due to the protection that silicone paint provides, Lime Bloom shouldn’t be an issue and your render aftercare and maintenance will generally be the same as above, simply remove any dirt with a light jet wash and/or soapy water and a sponge. Additionally, you can refresh the render finish with a brand-new layer of silicone paint to reinforce this protective layer.


In summary, it is extremely important that you continually monitor, and clean, the render of your property. This is one of the first things that people see when visiting your property, and as the saying goes ‘you never get a second chance to make a first impression’. Make sure that your property makes an impression for all the right reasons, and not because your render is dirty and damaged!

Take control of your building and take steps to ensure that yours is the property that people aspire to, how good does it feel to know that your property is the cleanest and most cared for in your area.

Keeping your render clean will maintain the value of your property and potentially save a large amount of expenditure over the life of your building. So, take a proper look at your building, see where your type of render fits into the above categories and consider what you need to do. Invest a small amount of money and time now and you could save yourself a whole lot of heartache and money in the future.