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What is the safest way to clean roof?

Updated: Feb 11, 2023



Cleanliness, safety, and appearance

Everyone wants to feel comfortable and secure, wherever they are. It is in order to ensure comfortable living conditions that not only high-quality materials and their installation are necessary, but also the constant maintenance of their serviceability, including cleaning. This issue is especially relevant in the case of the roof, regardless of what material was used to cover it: slate, shingles, or other options. Despite their reliability, they can be destroyed under the influence of external factors: moisture, fungus, moss, algae, temperature changes, etc.


Roof cleaning: why do you need it?

In addition to the fact that roof cleaning returns the home’s curb appeal, which affects the overall impression of the whole house, it is also able to extend using of this roof, because the price of such a service is much lower than the ceiling. Prevention of contamination is the key to cleanliness.


Roof cleaning methods

The specifics of this work directly depend on the type of roof and roofing material. In particular, slate surfaces that are vulnerable to the formation of moss, mold, and vegetation need cleaning. Modern roofs are easy to clean from dust, for example, with the help of an ordinary garden hose. However, if you only need to remove some loose debris such as dust or dead leaves from your roof, you can easily do this with a soft bristle brush. And of course, a good prevention would be to use a leaf blower sometimes, which removes not only leaves but also other debris.



Manual scraping

Manual scraping is used when it is necessary to remove complex pollution or vegetation. The main tool of this tool is a metal brush. But this method has several disadvantages: it takes a lot of time; this is rather time-consuming work, and the top layer of the coating can also be destroyed. An alternative tool is a grinder with a round brush.



Chemical cleaning/Soft washing

This is a method that uses low-pressure water.


There are many products designed for cleaning the roof, which effectively gets rid of moss and mold. Due to its special composition, bleach has the ability to harm other plants, not just algae. Therefore, it is worth watering all flowers and bushes in areas where bleach can flow before and after washing. An alternative option is to cover the plants with plastic.


If you want to prevent rapid evaporation of the solution when washing the roof, it is better to choose a cloudy day. Do not forget to take into account the characteristics of the roof material when choosing a cleaning agent.


Oxygen bleach lightens stains as well and is less harmful to the environment, but it doesn’t produce as immediate or dramatic an effect as liquid chlorine bleach.


Household laundry-strength chlorine bleach is a 5.25% solution of sodium hypochlorite and water. Even as a 5.25% bleach solution, it is quite powerful and must be usually diluted with water for safe use.


When using a product made for cleaning roofs with oxygen bleach, follow the directions on the container. The basic formula for cleaning solution, which sometimes can vary:

  • 1/4 bleach (6% sodium hypochlorite);

  • 1 gallon of water;

  • one-quarter of a glass of trisodium phosphate or other cleaners without ammonia because it is not desirable to mix it with bleaches (because their mix can form chlorine gas, which is poisonous).

You will need a garden pump sprayer for this washing process. Mix the resulting solution well and pour it into the garden sprayer, then treat the house with it and leave it for 15 minutes. When the time is up, wash off the solution with a garden hose.


Bleach washing your roof correctly will give a guaranteed result, but If you think the solution will immediately remove all moss growth from your roof, you should know it takes time, and the algae will wash away during rainstorms, and moss will eventually loosen to the point where it can be removed with a leaf blower.


The advantage of this type of roof cleaning is chemicals used in the process aren’t very expensive. So this method is affordable.



High-pressure washing

High-pressure washing is a very common method, but using this method requires special equipment -pressure washers.


The use of professional hydro-jet equipment ensures easy cleaning of the facade material since water supplied under pressure easily penetrates into the pores and removes accumulated debris from there.


Surface washing takes place under strong water pressure, which is controlled by a gun with special nozzles in the form of nozzles or mud cutters. To control the pressure in the device, a regulator is installed to adjust the strength of the jet, since a very weak pressure may not wash off the contamination, and too strong one can damage the outer layer of the material.



Pressure washer

The advantage of a pressure washer is that it can clean your roof up to 5x faster than your standard garden hose. For the process of cleaning the roof, you need a good source of water: a water pipe, a well, etc. The approximate consumption of water is 1500 liters per 100 m2 of the roof.


High-pressure apparatuses can be very different:

  • Household or professional;

  • With or without hot water;

  • With the supply of detergent through the foam nozzle or with a direct supply to the water through a special separate tank;

  • With electric or petrol drive.

Using a pressure washer you should remember proper safety precautions: wear safety goggles, do not stand on a slippery surface to avoid slipping, and make sure that your roof can carry you and you can do your cleaning without any fear because not all roof surfaces are designed for weight.


A standard garden hose or brush would take a lot of manpower and still wouldn’t get rid of or stop the algae growth.


Despite it seems to be the opposite, pressure washers use less water than a garden hose as they spray water through a more concentrated area.


With the help of high-pressure apparatus, you can easily clean the roof of overgrown moss and plant debris. Also, when using a special nozzle for cleaning pipes, you can clean the entire stormwater system.


Asphalt shingle roof

In the manufacture of shingles, fiberglass mats are combined with phenol-formaldehyde resin and an asphalt mixture, which includes chemical additives to better connect the two materials. At the last stage of production, the outer layer of the tile is covered with ceramic granules, which are one of the most important components of the asphalt pavement. The granules protect the tiles from UV radiation.


Such a composition of the material adds peculiarities to the care, so it should be taken into account which method can harm asphalt shingle roofs and which one is the best.



What is the best method of cleaning asphalt shingles?

High-pressure washing is not very good for cleaning roof shingles because this method can remove the shingles' granular surface and cause significant damage to them.


Also, because high-pressure washing is not recommended by shingle roof manufacturers, this kind of cleaning may void your warranty if your shingles fail.


A good option for cleaning asphalt shingles is to use a hose filled with water and bleach (in equal proportions). Rinse the roof with this liquid and leave it for 15-20 minutes, then rinse thoroughly with water.


How to clean metal tiles roof?

Over time, even a metal roof tile gets dirty and needs cleaning. If you want your roof to be cleaned correctly without scratching the surface, you should choose the right detergent.

Roofs that have a simple shape with steep slopes clean without human intervention (with rain or streams of meltwater). Roofs with an intricate configuration, with slope joints, abutments, and internal corners, need to be cleaned with special solutions.


Small debris containing dust particles collects in hard-to-reach areas of such a surface. Fallen leaves, needles, and pollen can accumulate on slopes located near trees or under their crowns. If you do not carry out regular cleaning, even moss appears from shadow areas.

Household detergents can be used to wash pitched roofs made of metal tiles:

  • dishwashing liquid;

  • solutions that do not contain strong reagents.

For this type of washing, you will need a mop, soft sponges, and a bucket. The roof is soaped, and the product is left on the surface for five to ten minutes for it to take effect. Then it is washed abundantly with water from a hose.


For heavy pollution, the ideal solution is a device with high water pressure. The pressure in the device should not exceed 50 bar for washing such a surface.


You should remember that hard brushes and brooms cannot be used for washing metal roofs, so manual scraping is not suitable in this case because it can damage the material and cause scratches that can cause bigger problems later. Also, be careful with detergents with abrasive substances and high-pressure washers on too high power.


Is it necessary to get rid of the growth on the roof?

Roofing bacteria can manifest themselves in a variety of forms and manifestations. You may think there is mold growing on your roof, but it could actually be moss, algae, or lichen. Metal roofs usually turn black with a greenish tint when they become saturated with organic plants. The growth can also grow on wood, bituminous tiles, ceramic and slate tiles, and many other substrates, especially if the sunlight in this area is not so frequent.


What damaging effects the growth can bring?

  • the appearance of cracks;

  • breaking of tiles or shingles;

  • roof leaks;

  • retains moisture which can have a damaging effect on the roof structure and surface;

  • wear down the protective layer on the surface;

  • adds weight to the roof, which can have a negative effect on the overall structure of the house;

  • can block drains.



Types of growth on the roof

Gloeocapsa Magma is that "black streak on the roof" (black algae). The appearance of black streaks on the roof, especially on asphalt shingles, is very characteristic of wet areas. This is most commonly found on asphalt shingles and can be algae spores, which live on the limestone in the shingles. As it feeds, it breaks down the limestone and eventually, if left untreated, takes over the entire roof. But in reality, while sometimes it looks like you just have a lot of debris or possibly defective material on your roof, it's often actually blue green algae (Gleocapsa Magma). Making it "totally black" even though it's not the color of the shingles themselves, but the algae that grow on the shingles.


Lichen. This type of growth is a combination of algae and fungi. They can combine and produce living organisms that then live on the roof. Lichens are firmly attached to the surface of the roof and this makes it difficult to remove. Lichen is attached with the help of its perennial root structure. If lichen growth is not prevented and removed in time, it can permanently damage your roof and even cause surface rust, which can eventually damage the structure and cause leaks.


Fire moss. This type of moss is less common than Gloeocapsa Magma, but is still very common on many roofing substrates, from cedar chips to asphalt shingles, and likes to cling and multiply. When fire moss gets out of control, it pushes up the shingles, allowing water to seep underneath and seriously damage your roof.


Also, other types of moss are similar in many ways to lichen because they have a strong root system called rhizoids that attach their body to the roof surface. The moss can then combine with the lichen to create a super-powered ecosystem of organic growth on your roof, collecting dust, dirt, and organic particles to feed on and keep growing.


Mold is a very bad plant that can grow on your roof. Roof mold can be found in brown or black areas, or it can accumulate as a smelly stain that can also be slimy. This type of growth likes places with high contents of moisture, such as rainy climates or areas.


Fungus is very similar to mold because it can grow in moist areas and cause health problems and raise a lot of bacteria. It can look like a powdery substance and have many different colors, shades, or tones. The colors of fungal growths can be pink, green, dark black etc.


How to get rid of the growth on the roof?

Obviously, the best option is a chemical cleaning method. If you want to clean the roof from moss and algae on your own, you must use the following proportions:


The first option is to use the active ingredient sodium hypochlorite 5% — 95% water. All roof cleaning operations begin with this weak mixture, as it is the mildest formulation that can be used to effectively clean a roof without damaging it. A soft-bristled brush is also used to remove stains of growth. It is recommended to use as few chemicals as possible and still achieve excellent cleaning. Many "professional" cleaning products include a large number of chemicals. Pay attention to this warning, because too aggressive chemicals can damage the roof, and unfortunately, this happens quite often.


The second option is 10% sodium hypochlorite — 90% water. This is the next option we go to if the first solution doesn't remove what needs to be removed. Again, we use the least amount of chemicals along with a soft bristle brush to break down organic growth and provide superior cleaning as we go.


There is also another cleaning solution: 20%-50% sodium hypochlorite — 80%-50% water. This is the most aggressive solution, and only professionals should try to use it. This compound has a high potential to damage your roof if used improperly.



How to keep the roof clean?

Sometimes it may seem that the cleaning process takes a lot of time, but if there is an opportunity to prevent major problems, it is better to do some procedures for roof regularly.


What can you do to keep it clean?

  • Check the condition of your roof from time to time to spot contamination in its early stages.

  • Regularly use a blower to get rid of leaves, branches, and other debris on the roof, which can accumulate dirt and cause the appearance of growth and vegetation.

  • Trim branches above the roof to prevent them from falling on and damaging your shingles.

  • Don’t forget to clean gutters, especially before a storm. If the gutters are backed up, they can contribute to the deterioration of roof materials.

  • Always check your roof after storms and other extreme weather events.

  • A well-insulated attic will help maintain the condition of your roof. If the attic is not properly insulated, this can lead to excess moisture, which can accumulate moss and algae.

Do you want to do the cleaning yourself?

If you still decide to do the cleaning yourself, you should take care of your safety. If you are not sure that you can do it yourself, it is better not to risk it.


Roof cleaning is a very dangerous activity, especially when it’s wet, so be sure to take adequate safety precautions.


Take safety

Bits of Advice if you want to clean the roof by yourself:

  • Avoid cleaning on steep roofs without safety ropes;

  • Wear slip-resistant shoes with traction;

  • Be careful in slippery areas;

  • Wear safety goggles to keep chemicals out of your eyes (if you choose soft bleach cleaning);

  • Some cleaning solutions can harm you and your skin, so read instructions before using them and cover your skin if it’s needed. Use gloves.

Professional roof cleaning

A professional cleaning will save you not only from doing dangerous work but will also help to improve the appearance of your house and will eliminate the factors that damage the roof covering. After all, there is a famous phrase that a roof can age a house for decades if there is no care or the use of inefficient methods.


All actions are carried out by specialists with professional equipment and in compliance with all safety regulations. Since working at height requires special equipment and skills, if you doubt your safety, it is better not to perform such actions yourself.

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