The actual roof cleaning methodology is different from roof washing and worth talking about because there is still some ambiguity in the market when it comes to what you ask for and what you get.
First of all – roof cleaning is important, building owners be reminded that a roof is a big deal, they are not cheap to replace and a little bit of cleaning maintenance can extend the life span of a roof significantly – likely double if not more.
Before we go on – if you want to know the condition of your roof and do not have easy access, ask us about a drone inspection.
Here is what you need to know about roof cleaning:
If your roof looks something like this, it is pretty dirty, just like your car would be if you didn’t wash it for a few months.
Dirt gathers on the flat tray profile and on the ends of the iron, especially evident on a low pitch roof like this and most other commercial roofs. There are likely moss or lichen spores in amongst this lot but not immediately visible as a green tinge just yet.
A relatively easy clean, it will come up well with minimal effort.
If your roof looks something like this – it is obviously super dirty, and it also has moss and lichen growth – this probably hasn’t been cleaned or treated for moss in the last 10 years!
The roof coating and the membrane gutters, in this case, are at risk of been penetrated by lichen and thus exposed to the elements. In a salt zone like most of coastal California, corrosion will set in quickly and start to rot the roof.
This roof has been left way too long and it will involve a considerable amount of work to clean it up.
You have 3 choices to cleaning your roof:
Roof Wash #1 – A moss and lichen spray treatment (aka Soft Wash)
This is a high-volume soaking using a benzyl ammonium chloride solution – designed to saturate the roof and kill any moss and lichen spores. It remains active for a long time and is reactivated when wet – so every time it rains a bit more washes off and away.
The Good: Low cost, effective, lasts longer, usually uses less access as a larger area of roof can be sprayed from a distance.
The Bad: Results are not instant, heavy on chemical use, rain water collection systems have to be disconnected for several months after to prevent contamination, does not remove dirt build up, does not remove bird droppings or debris on the roof surfaces, does not clean gutters.
Note – if your cleaning company mentions they’ll be using bleach on the roof – tell them to take a hike…
Roof Wash #2 – Low-Pressure Chemical Clean
This is just like your Sunday morning car wash: apply the soap, let it work and wash off a using low pressure water blaster. This is a good method for many roofs that have a medium/low level of dirt as pictured in Example 1 above.
The Good: Instant and effective, removes all dirt, debris and bird droppings, gutters can be easily washed out at the same time.
The Bad: Potential contamination from chemicals (if not managed correctly), rainwater collection systems should be disconnected for the duration of the clean, slower process, complete fall arrest systems usually needed, noisy – more disruption to building occupants low pressure potentially exposes leaks.
Roof Wash #3 – Pressure Wash
A straightforward med-high pressure roof wash using plain water – sometimes heated to 50 – 60 deg for extra cleaning effect. This is a good method for all metal roofs, especially those with high level of dirt and lichen as pictured in Example 2 above. Even so – higher pressure and even hot water may not remove the most stubborn lichen spores or roots, so it is good practice to follow through with a moss treatment spray after cleaning a badly soiled roof.
The Good: Instant and effective, removes all dirt, debris and bird droppings, chemical-free, gutters can be easily washed out at the same time.
The Bad: Can be slow – depending on the level of dirt, complete fall arrest systems usually needed, noisy – more disruption to building occupants, potentially exposes leaks with higher pressure.
Note: not everyone who provides you with a quote for your roof wash will have inspected the roof up close – so will default to the 1st option as it is low risk. By the time you remember to check the results in 3 – 6 months’ time it’s a bit difficult to account for.
The cost difference between option #1 and options #2 & #3 could cost potentially double or more – so it is important to understand…
…the bottom line – what you are paying for versus your expectation of the scope of work for your roof clean
…that you know what result you want – instant results (for pre-sale) – or are you happy with a more drawn-out result?
…the numbers, roof cleaning is high-risk work by default, and the largest cost factor is time. If the quotes vary enough to raise your eyebrows, then it begs the question;
– What safety practices are being followed?
– How long will it take?
– What method has been quoted for?
A clean roof is easy to keep clean
Sounds obvious but it is good to remember that lichens only form if the environment is right for them. They need moist air, a substrate that doesn’t move (i.e a roof), nutrients (dirt, bird poop, moss), and light, all which are in ample supply on your roof. If you keep the dirt down, they will struggle to form.
We recommend an annual roof clean. That is the recipe for a long-lasting roof.
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