How to Clean a Building Exterior

How to Clean a Building Exterior

We have all seen the highly satisfying pressure washing videos, showing the drastic difference between the before and after of a jet wash! While these are great to watch, pressure washing may not be the greatest option when cleaning a building exterior. There are several other alternatives to this, which we will evaluate further in this article.

All aspects of your building require regular cleaning and maintenance. From your roof to your driveway, each area of your building’s exterior will benefit greatly from a bit of TLC. You will see a noticeable improvement in your property’s aesthetics, and your building may even go up in market value!

There are numerous health benefits to having a clean property, from preventing slips and falls, to avoiding respiratory issues. We will discuss how you can ensure that your building is a safe and healthy place to be, just with simple cleaning processes.

Having an unclean building exterior can lead to structural problems as the growths can apply additional pressure to your building’s infrastructure. Unwanted pests can also be attracted to dirty roofs and settle in them. This can all be avoided with regular cleaning.

When it comes to finding the right tool for cleaning your building exterior, there is much discussion between pressure washing and soft washing. Soft washing is often overlooked but can be far more effective in making your building sparkle.

This article will discuss the benefits of each method and where best, you should use each method on your building. Keep on reading to find out how you can turn your building from drab to fab!


In this article, you will find:

Why You Should Clean Your Building Exterior

Health Benefits

Cleaning your building exterior effectively yields numerous health benefits because soft washing eliminated potentially harmful substances. When building exteriors are left unclean, substances such as pollen, mildew and bird droppings are allowed to build up. If left untreated, persistent exposure to this can lead to breathing problems, allergies, and disease. When pressure washing is used regularly, this harmful build-up can be prevented, stopping these dangerous consequences from developing.

Grease, mould and other substances found on pavements and walkways can become extremely slippery. By washing these substances off of walkways, slips and falls can be prevented. Whether you are trying to prevent nasty falls, or just cleaning your walkways for visual purposes, power washing your building exterior makes your entire property safer.


There is no doubt that the primary motivating factor when cleaning your building is to improve the look of your home. The satisfaction that you feel once your building has been transformed will definitely make you want to wash your building again! As well as the satisfaction and the general pride you will feel, there are practical reasons as to why you should take the time to clean your building exterior.

A clean building exterior has the potential to massively bump up your building’s value. By soft washing your building correctly and regularly, you can boost your building’s kerbside appeal. Kerbside appeal refers to the first impression that people get when they view your property and can be a huge factor when potential buyers are making their purchasing decisions.

Although you may not be in the market for selling your building at the moment, regular cleaning will keep your property’s value high, and will save you a huge job when you do come to sell it!

Cleaning Building Exterior

Cleaning Building Exterior

Areas to Target


Having a roof over your head is one of the most important the things, both literally and figuratively! Although the roof of a building is vital, it is often overlooked and disregarded as an area that does not require any care or maintenance. Leaving your roof unclean can lead to a plethora of issues, many of which are extremely expensive to resolve.

A roof is an ideal place for moss, mould and lichen to grow as there is a large amount of moisture on roof tiles due to the rain and dew. The warmth of your building then causes a rise in humidity, making your roof the ideal breeding ground for a variety of organisms.

Moss can be especially damaging to your roof, as it absorbs and holds large quantities of water. This additional weight puts unnecessary pressure on your roof, which can lead to costly structural issues. When moss is allowed to grow, it can grow under the roof tiles, leading to water damage inside the house.

Your roof is probably covered in lots of dark spots, which appear to be unsightly but harmless. However, this is not always the case, as these are algae spores which when left to grow can develop into dangerous mould and fungi.

When mould and fungi are present on any part of your building, it can lead to harmful respiratory problems. This can be especially hazardous for young children, individuals with asthma and elderly people. In addition to the structural issues that these spores can cause, the impact that moss, mould, and lichen can cause to your property’s roof is severe.

Unfortunately, pests such as birds have a strong attraction to roofs that have a build-up of moss on them. It provides a food source to many birds as smaller insects often live in the moss. Birds will always nest where they are close to food and water sources, both of which moss provides. Nesting birds can quickly cover your roof with faeces, allowing more bacteria to grow, as well as damaging your roof tiles through repeated movement.

If you have existing gaps and holes in your roof due to poor roof maintenance and cleaning, there is also the chance that birds and bats will squeeze through these small gaps and nest inside your building. This, in turn, can bring more harmful bacteria and potential diseases into your building.

To keep these unwanted visitors away, you should ensure that your roof receives regular cleaning and maintenance. When the moss is cleaned off of your roof, birds become far less attracted to your building and present less of a problem for your property.

Cleaning Your Roof

There are a variety of ways that you can clean your roof, from handwashing it with a hard-bristled brush and scraper, to pressure washing and soft washing. Whilst pressure washing can blast away the problem causing dirt and moss, it can cause further damage to your roof tiles. Due to the harsh pressure that is used, you can strip the tiles of their colour and can break roof tiles, leading to an expensive fix.

Soft washing is the ideal cleaning solution when it comes to cleaning your roof. Using a roof specific surfactant, you can quickly and easily remove the dirt from your roof, without causing any unwanted damage to your roof. When soft washing your roof, you should start at the top, and work your way down. This will ensure that there is no build-up of debris.

It is important that before you wash the roof, you make sure that the gutters are clear of any large pieces of debris or dirt. This will allow the water from the soft washer to run off of your roof smoothly. When you do clean your roof for the first time in a while, make the most of the summer months and their hotter temperatures, as well as the extra daylight hours.


When it comes to the walls of your building, there are a variety of different materials that your building could be finished with. Each of these materials will need slightly different care and attention when it comes to cleaning your building.

It is important to note that if you are using any pressure washing tools, you will need to be especially careful of your windows. Soft washing only should not cause any damage but using high pressures can chip and damage the paint on your window frames and can even break old windows.

The most common of building materials is the classic red brick, also known as mortar. On older houses, the mortar can become less stable and additional care needs to be taken when it is cleaned. Pressure washing on brick will cause damage to your walls and should be avoided. Soft washing at a low level will work well in cleaning off watermarks, moss and general dirt.

Wood siding is another common material used on building exteriors, giving the building a classic and homely feel. When cleaning wood siding with high pressure, water can find it’s way up and under the siding. This can lead to many problems such as warping, wood rot and mould, as well as damaging electrics and insulation.

It is important to use a low pressured soft washing technique to avoid this damage. When cleaning the wood siding, you should always aim the water in the direction of the grain, not against it. This will ensure that no water sneaks under the panels.

Render can be found on most houses, offering a modern and attractive finish to buildings. Render is typically made from lime, but other components such as cement and acrylic can be used. Whilst render is designed to last for decades, it is highly susceptible to staining.

Much like your roof tiles, moss, lichen, and algae enjoy growing on render walls. If they are allowed to grow on your render walls the render can rot prematurely and can cause cracking to the wall. When cleaning your render walls, you should take care of any areas that have cracks or appear to be peeling off of the wall. Use a soft washer with a strong render-specific surfactant to remove the moss, lichen and algae whilst protecting the render from any additional damage.

Regardless of your wall material, it is best to take extra precautions to ensure that you minimise the risk of any damage. Always mix the chemicals to the correct concentration, and where possible try and use the correct surfactant for the surface that you are cleaning.

If you have walls or surfaces that were painted before 1978, you should leave this cleaning to a professional. Paint often contained lead before this time, and you do not want your family or anyone to breathe in these paint chips and particles. If you are not sure, always ask a professional.


Pathways and walkways get a lot of use, and therefore get a lot of wear and tear as a result. Pathways can get dirty very quickly, and often have poor drainage, allowing dirty water to pool on their surface. This can create a breeding ground for algae and moss.

Often on patios, you will see dark black spots. This is black algae. This grows very quickly and can be quite stubborn when you try to clean it off of your walkways. It also makes your patios very slippery, especially when it is wet, increasing your chance of slips and falls.

This slip hazard can be easily removed by pressure washing your patio or through soft washing. There are lots of surfactants on the market that explicitly target black mould, and work very quickly and effectively on pathways and patios.

If you have decking, you should clean this by soft washing the wood with a wide spray. Decking is surprisingly rather soft, and intense pressure can cause irreversible damage to the wood and your decking. There are specific surfactants available for woodwork, often including UV protection to help keep your decking looking better, for longer.

If you have a block paved driveway, you should avoid using a pressure washer to clean this. When pressure washers are used on block paved areas, the sand that is used in between the blocks will be blasted and washed away. If you do decide to pressure wash your block paved drive, you should be prepared to refill the edging with sand before you use that area.

Cleaning Building Exterior

Cleaning Building Exterior

Choosing the Right Tool

Power Washing

Power washing and pressure washing are often confused with each other, with many people thinking that they are the same thing. However, there is one significant distinction which differentiates them. Power washing is much like pressure washing, but it uses hot water instead of cold. This can be very beneficial when needing to sanitise areas as no additional chemicals are required. The use of hot water also means that it breaks down organic materials exceptionally well.

Power washing machines are heavy-duty, and they are a big piece of kit. You only tend to find these in industrial settings and some commercial settings. Many companies will offer power washing as a service, as proper training is needed to operate a power washer. This probably is not the best option when you are thinking of cleaning the outside of your home, as the power washer’s ability to break down organic materials so well can cause lots of unwanted damage.

The majority of all building exteriors do not require anything as fierce as power washing, so it’s best to leave this one to the professionals for heavy-duty jobs.

Pressure Washing

When most people think about cleaning their building’s exterior, they think pressure washer or jet washer as it is seen to be such an effective way to clean a variety of home and building surfaces.

Although pressure washers do not heat the water, the sheer force of the water that gets blasted out is still enough to be dangerous. The water pressure is enough to carve a pumpkin with and even cut through your finger, so do be careful!! When you use pressure washers, you must be at the correct distance away from the area you are cleaning to avoid wearing down and damaging certain materials.

Pressure washing is designed for cleaning hard surfaces that are walked on, such as stone pathways and patios. Surfaces that are hardwearing but have deep grooves that dirt can get embedded into are great for cleaning with a pressure washer. However, the exterior of most buildings isn’t best suited to being cleaned with a pressure washer, as the pressure per square inch (PSI) is too large and causes damage to exteriors.

Pressure washing should be used for materials such as hard brick paths and concrete but should always be used with caution.

Soft Washing

You may think that soft washing has absolutely nothing to do with pressure washing due to its name, but that’s not the case! Soft washing is when a pressure washer’s PSI has been reduced to less than 1000 PSI. As well as reducing the pressure, the tip of the hose on the pressure washer is replaced with a widening tip. This also reduces the point of pressure, allowing cleaning to take place, without the risk of damaging building exteriors.

With soft washing, you can use specialised cleaning solutions with it. These cleaning solutions are typically eco-friendly, but still, break down the dirt and organisms that live on surfaces.

The real benefit of soft washing is that there is a significantly smaller chance of causing damage when cleaning. Although additional chemicals are added, when used correctly, soft washing is a safe, efficient and easy way to clean a building’s exterior, without having to stress about causing any damage to building materials.

Soft washing should be used on materials such as wood for siding and decking, stucco, metal buildings, and the majority of building exteriors. All substrates that are especially hard to get clean with just pressure or would be damaged if high pressure was used on them are the perfect candidates for the Soft wash treatment!


Now that you have decided what method will be best for cleaning those building exteriors let’s talk about what else you are going to need and what you should prepare before starting the cleaning process.

Cleaning Solutions

You have probably realised by now that soft washing is most likely the best option to clean your building exterior, so you have your soft washing skills at the ready! However, there are a few essential things that you need to do before you can start working on making your building shine!

You should start by buying Sodium Hypochlorite and a surfactant. Most DIY shops sell these, and there is a plethora of these available online. Sodium Hypochlorite is the primary component in bleach and is a great disinfecting agent. It is highly effective for the disinfection of viruses, bacteria, fungi and mycobacterium. Sodium Hypochlorite is also fantastic at removing any unwanted odours. When you use this, it is imperative to read the information on the container and to mix the correct amount.

There is a considerable variety of surfactants on the market, and you should select the most suitable one for the material that you will be cleaning. If you are cleaning a variety of materials it is best to invest in a multi-use surfactant that will be suitable for all the materials that you will be targeting. These substances are inexpensive, lasting for multiple cleans as not a large quantity is typically needed.

When mixing these you should make sure that you are using the correct amount of each substance. If you use too much of the surfactant it will produce soap suds that can leave unwanted marks on surfaces. If you have added too much Sodium Hypochlorite you can cause damage to sidings and exteriors. As long as you follow the directions on the packaging, you should not have any problems with this.


When using any cleaning products, it is extremely important to pre-soak the surrounding landscape. Ensure that all the plants and grass nearby have been thoroughly pre-soaked with water before you begin the cleaning treatment. Making sure that the surroundings have been generously soaked keeps all your plants happy and prevents any unwanted effects on the foliage you may have around your building.

Cleaning Building Exterior

Cleaning Building Exterior

The Process

Applying Your Mix

Now that you have given the surroundings a good soak with water, you can start to apply your mix of Sodium Hypochlorite and your surfactant. You can apply this very generously. There is no need to worry about over-applying this if you have mixed the chemicals correctly for the substrate that you are cleaning. To get the best results, leave the solution on for 5-10 minutes, or longer depending on the surfactant that you use. Always refer to the instructions on the packaging if you have any concerns.

Clean a small test area to check if an additional layer of the cleaning solution should be applied. Depending on the material that you are cleaning and the surfactant that you are using, the number of layers required to achieve the desired result may vary. Vinyl siding, for example, typically only requires one layer of application, with a dazzling impact on dirt and mildew in just five minutes. On the other hand, more porous materials such as stucco require additional layers of application to work effectively.


You’ve pre-soaked the surroundings, applied your cleaning solution and taken a deep breath. It’s time, you are ready to see the fruits of your labour! Using pure water only, give your building a thoroughly good rinse and watch the results appear in front of your eyes.

Make sure that you give everything a generous rinse, ensuring that no cleaning solution is left on the building and that all chemicals have been thoroughly diluted. Your building should be left looking sparkling and clear of dirt, mildew, and bacteria. You can repeat this method as many times as is required to achieve your desired result.

When Should You Clean Your Building?

Cleaning your building exterior is probably at the bottom of your jobs list, and maybe something that you have been putting off for months, but there is no better time than the present! That being said, you should avoid cleaning your building exterior in freezing conditions.

The summer months are the ideal time to clean your building exterior. The temperature is significantly warmer, meaning that the surfaces of your building will dry quicker and the days are longer, meaning that you have more time to focus on doing a fantastic job of cleaning your building.

Once you have cleaned your building for the first time in a while, you should repeat the cleaning process a month later. This will ensure that any dirt or spores left on your building’s exterior will be cleaned off. After this, you should aim to soft wash your building every 3-6 months, depending on the severity of the dirt and mould your building has.

Each time you clean your building, this job will get quicker and easier to complete. With regular cleaning and maintenance, it will be just like cleaning your car or weeding the garden, a task that can be done in a matter of hours, yielding great results.

By cleaning your building every 3 months, dirt, moss and algae will not have the opportunity to grow and you will see a significant reduction in the pests that your building attracts. As well as this, you can feel happier and healthier about your building, knowing that the entire outside of your building is clean, and void of any nasty bacteria.

Health and Safety

Before you clean your building, you should be aware of the risks associated with it. It is important to use a sturdy ladder, that is properly fixed on to your building and is stable before climbing it. Never use a pressure washer while working on a ladder, as the powerful recoil of the spray hose can knock your balance and can cause you to fall off the ladder.

When cleaning your roof there is the potential that you may make existing damage worse. For example, if there are loose edges or cracked tiles, you may break these beyond repair. Before you start on any cleaning, check for any cracks, loose tiles or edging.

Always wear safety glasses when you are operating a pressure washer. This prevents any debris from going in your eyes as well as stopping any of the chemical cleaning solution getting in your eyes also.

If you have any powerlines, electrical masts or electrical outlets near your building, take extra care. Make sure that you maintain a minimum distance of six feet when you are spraying water anywhere near these. Do try and avoid spraying these altogether.

When you have finished using the pressure washer, turn it off at the switch, then turn the tap off. After this squeeze the trigger on the spray wand to release all of the pressure and water that is in the system.

Make sure that you turn off the pressure washer when you are not using it, and that the water is off also. If you change nozzles, ensure that the pressure washer has been switched off.

Cleaning Building Exterior

Cleaning Building Exterior

Top Tips

We have discussed the building cleaning process, the best tools to use and why you should clean your building, but we still have more expertise to share! Here are just some of our top tips when it comes to cleaning your building exterior.

When it comes to cleaning your building exterior, we highly recommend using the soft washing technique. By soft washing your building, you can achieve highly effective and impressive results, all whilst ensuring that your property does not get damaged in the process.

Roof Top Tips

When you clean your building, you should start from the top of your property, and then work your way down. It is best to split each area up and target it on different days, starting with your roof. Before you soft wash your roof, you should try and remove the worst of the moss and other growths. As many roofs do not get cleaned until there becomes a problem, there can often be a large build-up of moss.

If you have not washed your roof in a while, you should target these large moss build-ups with a scraper. This should only be done if your roof is safe enough to do so, if you are unsure of this, consult with a professional. If scraping is not an option, you should use a water-fed pole to reach the top of your roof.

If you have dirty gutters or an excess of debris on your roof, you can use a tarpaulin to lay on the surrounding area to catch any dirt or debris. This will prevent your gutters from getting blocked and will save you another job!

It is important to pre-soak your plants and lawn before you tackle begin to clean your building. As we have discussed, thoroughly soaking your plants and lawn with water will help protect them. You should also rinse them with copious amounts of freshwater after the treatment. This ensures that all of the chemical cleaning solutions are diluted and will not harm your plants.

Wall Top Tips -Cleaning Building Exterior

When you clean your roof for the first time in a while, you may need to repeat the cleaning process. Before you clean your roof for the second time, you should wait a minimum of 48 hours. Moss takes 48 hours to go brown, which means that it is dead. If all the moss has turned brown there is no need to repeat the cleaning process, as the wind and rain will remove the remaining dead moss. If the moss is still green after two days, you should repeat the cleaning process.

Once you have cleaned your roof, we recommend that you move on to the walls of your building. Make sure that you are using the correct chemicals for your property’s wall. Like when cleaning your roof, you should target any areas of excessive moss and mould build-up with a hard-bristled brush and clean water.

Another tip for cleaning your walls is to ensure that you do not just clean your walls in strips. Cleaning down your wall line by line can make your walls appear to be streaky. Once you have cleaned an area horizontally, use a circular motion on the spray wand to reduce the appearance of any lines or streaks.

When you are cleaning your walls, we recommend putting bin bags or tarpaulin on your window ledges. This prevents them from becoming dirty as a result of the moss and dirt being washed off of your walls. As you should never use a pressure washer on a window, this will save you from having to hand wash your window ledges and frames afterwards.

Walkway Top Tips – Cleaning Building Exterior

When it comes to cleaning your property’s walkways, you should take additional care as the surface may become rather slippery. Our top tip for cleaning walkways or patios is to start as close as you can to the building, and then work your way away from the building. You should never aim the water in the direction of your building as this will cause mud and dirt to splash up on to your property.

If your walkways are on a slope, you should start at the top of the slope to help the water run-off effectively. Once you have cleaned an area of the walkway, you should use a wide stream to flush the dirt down the path or patio. This will help you get a better clean and will stop so much dirty water splashing everywhere.


Cleaning any building exterior is a mammoth task, but it is worth all the effort that you put in. There are countless benefits to cleaning your building, both from an aesthetics perspective and from a practical view.

When a building is left uncleaned for a long time, algae, moss, mould, lichen, and dirt is allowed to build up. If left untreated this can cause severe problems for your property and can even negatively impact your health.

Mould can cause severe respiratory issues for children, those with asthma and elderly people. As well as this, mould spores can be dragged into your property when your outdoor pathways have a build-up of mould, which can lead to further breathing issues and generally poor health. Large areas of mould should be scraped and then soft washed to reduce the risk to individuals.

As well as mould directly causing health issues, pests are attracted to unclean roofs and can cause additional complications by damaging the inside of your roof, and by bringing in harmful diseases and bacteria into your property. By ensuring that your roof is clear of moss and mould you will be able to deter these pests from causing any problems for you and your property.

Structural issues can occur when moss and mould grow underneath tiles, in between cracks and on your roof. This can apply additional pressure on to your walls, foundations and infrastructure.

Through proper cleaning and regular maintenance, you can prevent these issues from occurring, all whilst brightening up your building in the process. By investing the time and money in regular building cleaning, your property will benefit and its value has the potential to increase.

When it comes to the cleaning process, you must check what material you will be cleaning. Different materials respond differently to treatment, with some materials being more sensitive and easily damaged. Generally, soft washing is suitable for the majority of all surfaces. Power washing should be avoided, and pressure washing should be used with caution as it can cause unwanted damage.

When soft washing your property, It is important to use a good surfactant. Make sure that you mix this correctly and always follow the instructions on the container. When the cleaning solution is mixed correctly, you will be able to do a highly effective clean which will destroy the moss and mould at the root, preventing them from growing in the future.

You can repeat the cleaning process after a few days, and as many times as you need to as long as the cleaning solution is at the correct concentration. When you do wash your building, make sure that you have pre-soaked the surroundings in clean water to prevent any accidental damage.

As with everything, there are associated risks when it comes to cleaning your property. Make sure that you are wearing safety goggles, a face mask and gloves when operating the machinery. If you do not feel confident in cleaning any areas of your building you should contact a professional.

Deciding to clean your building is a no-brainer, with the benefits of doing so speaking for themselves. As long as you have good equipment, the correct cleaning solution, and motivation, you will have your building sparkling in no time!

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