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Residential Roof Washing in Canada

Residential Roof Washing

When it comes to roof washing in Canada it is very important to first identify the type of roof you are working with. Then you will need to make sure you have the knowledge and experience to understand the proper way to safely and effectively clean that type of roof. A good understanding of the current condition of the roofing material is also important because you will not want to waste time or money on cleaning a roof that should be replaced.

In this post we will discuss 4 types of roofs that we commonly see in Canada and we will discuss determining the:

Type of Roof and Characteristics

Condition of the Roof

Process to Safely Clean the Roof

Ongoing Maintenance to Help Prolong the Life of the Roof.

Understanding what material the roof is made of is very important because this will allow you to easily:

Determine the condition it should be in given the age of the roof

How to clean plus maintain

The residential roofs that we most commonly see in Canada are:





Now let's break down each type of roof.

Asphalt Roof

Asphalt can be identified by its flat, sleek look and the sand granules that are present on the top side of the shingle. They are a great choice as they are one of the most affordable shingles, they reflect the sunlight very well and are actually fire resistant so they are quite often used in areas that are prone to wildfires or in communities where houses are built very close to each other.

A new asphalt roof will be very clean on all sides of the house, it will not be missing any sand granules on the face of the shingle, none of the shingles will be cracked or curling up. The longer the roof is exposed to the outside elements the more it will start to show signs of wear and tear.

To clean an asphalt roof you should first brush off all of the heavy moss that will be growing at the overlap of the shingles. A great way to do this is by attaching the moss brush to a pole and manually brushing the moss that easily comes off with the first pass of the brush on the shingle. Then we suggest that you either leaf blow (if its dry) or gently rinse (if its raining) all of the moss into the gutter system. Then you will want to fully clean out all the gutters. Now comes the magic. You will want to spray the entire roof with a 4-6% mixture of sodium hypochlorite and roof washing soap evenly over the entire roof. 

After the spraying is complete you can leave the mixture on the roof and let the rain, wind, sun & snow naturally clean up the roof overtime. Keep in mind that after the spray, the roof will look much better. Plus, it will continue to look better and better over the next few months and the best part is that you have not comprised the integrity of the roof by using high pressure. The brushing of the roof can be slightly harmful to the shingles but if you maintain the roof you will never need to do this again and we truly feel that the benefits of brushing greatly out weigh the negatives.


If you choose to skip the brushing you can choose to simply "Spray & Walk Away" This means that you will just spray the roof and let mother nature rinse it for you. This works well for newer roofs that are under 7 years of age. The "Spray & Walk Away" method works great but will take much longer to clean up naturally. As well, you will want to plan an extra gutter cleaning that year to clean out all the extra debris that has died and rolled into the gutter system because you decided to skip the brushing. Another great idea is to add Gutter Baskets to the home to help keep the gutters flowing in between cleanings.

To maintain this clean looking roof you can simply re-spray the roof every 2-4 years. By re spraying and keeping up with the regular maintenance you should never have to brush the roof again. Be sure to always clean out the gutters prior to spraying the roof to allow for proper drainage of the mixture.


Cedar Roof

Cedar roof are easy to identify because the shingles are made of wood. The shingles are quite big and often different sizes.

A new cedar roof should have a rich colour and the shingles should not be lifting or curling at all.

To clean a cedar roof you will want to first leaf blow or gently rinse all the loose debris off of the roof. Then you should clean out the gutters to allow any additional water needed during cleaning to have a place to drain. Then, using a pressure washer you will want to pressure wash all of the shingles. It is best to have a pressure washer that is rated for 4-8 gallons per minute. What you will want to do is use a pressure washing tip that is rated for 2xs more than what your machine is rated for. Basically if you are using a 4 GPM unit then you will want to use a 8 GPM tip or nozzle. This will cut your pounds per square inch output by 50%. This will allow you to keep you engine at full throttle but greatly reduce your PSI. The max PSI that you will need will be no more than 2500 PSI. After you fully pressure wash the roof you will want to put a coating on to the roof. This is a type of oil for the roof that will help hydrate the roof and will protect the roof from the elements such as rain and uv light. 

A cedar roof will not need to be re cleaned very often but then next time it needs a good clean it is a good idea to complete this exact same process over again. Another great idea to help maintain the roof is to leaf blow all the loose debris off of the roof at least once or twice per year. It's a good idea to do this when it is warm and sunny out and the roof and debris is dry.


Metal Roof

Metal roofs are not made up of shingles and instead they are usually large sheets of thin metal that are forged or crimped together. Often the individual sheets are corrugated and are very often used in areas that are prone to snowfall as the metal roof will allow large accumulations of snow to slide off easier. Metal roofs do not grow moss on them naturally but it can build up if there is an overhanging tree that is shedding on to it. The moss will not grow roots in to the surface like it will on an asphalt roof.

A metal roof that is in good condition will not be bent or have any screws that are backing out of their holes plus if it is painted it will have a nice even coat.

For cleaning there are a few options. You can spray the entire roof with a mixture of 2-3% sodium hypochlorite and roof washing soap. Then, you can either pressure wash it off for an instant clean look or you can leave it on there and let it naturally clean up. Often people will leave the mixture on the roof because walking on a metal roof after spraying it with soap can be very slippery. You could always just pressure wash it without using a detergent however, it will take much longer to clean, you will need much higher PSI which could cause damage to the roof or the paint plus all of the growth will grow back much quicker since you have only removed the organic growth instead off killing it at the root.

Every 2-4 years you can simply spray the same mixture on to the roof and let it dwell and naturally rinse away. The timeframe of how often you will need to respray heavily depends on the pitch of the roof. The steeper the pitch, the less often it will need to be re cleaned.


Concrete/Tile Roofs

Concrete/Tile roofs are very heavy and often painted. This paint adds an extra layer of protection to the roof against the elements. They are easily noticeable because of the very uniform appearance as each tile is formed to be identical in size and shape. Concrete roofs do not absorb heat as much so they will keep your home nice and cool in the summer months and warm in the winter by helping keep the heat in your home from escaping.

Concrete roofs should not have any cracked or broken shingles. These shingles can be easily replaced and should be done so prior to cleaning the roof.

To clean a concrete roof you could just simply pressure wash it but again there is too much PSI needed on every spot of your roof that it can lead to damage. It is also very time consuming and dangerous to be working on a roof with a pressure washer. What we have found works best is to first leaf blow or rinse down the entire roof. Then, we clean out all the gutters. After that we spray the roof with a 4-6% mixture of sodium hypochlorite and roof washing soap. After the mixture has been on the roof for at least 10-15 minutes you can start pressure washing it with up to 2500 PSI using the same method as mentioned in the “Cedar Roof Wash” section. After fully washing all of the algae and moss off of the roof and into the gutters you will want to re clean all of the gutters and install your Gutter Baskets. Then you will want to re-spray the entire roof again with a 4-6% sodium hypochlorite and roof washing soap mixture to kill every spore of organic growth at the root to slow down the re growth process. This will keep the roof cleaner for a longer period of time.

To keep a roof like this clean it is very similar to a cedar roof. You will want to leaf blow the roof when it is dry 1 or 2Xs per year plus re-spray the roof every 4 or 5 years.

Now, depending on the climate of where you live there will be different effects on the roof overtime. Areas with lots of sunlight will be more prone to UV damage and oxidization. Places that are cold may see more cracking on the roof and places that are wet and have lots of moisture will see more organic growth such as algae, moss and lichen.

Identify your climate, type of roof, best way to clean it safely plus how to maintain it.


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