If you live in an area with trees, rain, and limited sunlight you are probably familiar with good old green moss growing on your roof. Some people may enjoy this look but as I’m sure you’re aware this can wreak havoc on your roof and eat away at your shingles. Let’s get rid of it.
Generally moss can be removed at any point of the year.
There is no specific “ideal time of year” except whenever you have the time to do it. As a rule most roofs and gutters should be cleaned every 6-12 months to prevent potential damage, growth of moss, or needing a new roof much earlier than necessary.
That being said as having cleaned thousands of roofs I do prefer to clean during the spring and summer months when its warmer and less crappy to be outside and up on the roof.
The moss is also a bit drier and a more vulnerable to chemical treatments.
You can see though that moss is usually green in early spring and winter and then dries out spring and summer.
Sometimes I do find it actually easier to manually remove when it is wet and swollen in the winter months and early spring. But if you are looking to more apply chemical and walk away, pick a time of year when it’s a bit drier and not in the rainy season that’s for sure.
As far as getting rid of this pesky moss we first need to understand a bit about how it grows and what preventative measures we can take against it.
Why keep moss off your roof?
If you’ve ever seen a sidewalk that has trees growing next to it guess what happens next? The roots grow up and under the concrete and cause it to split and break. This is similar to what happens when stuff like moss grows on your roof.
While it doesn’t really have roots, moss is an organism that can still grow up under your shingles and hold moisture on the roof much longer than it should be.
This can cause your roof to need to be replaced YEARS earlier than it should have to be.
As the owner of a roof cleaning business one of our main jobs is roof moss removal and keeping moss from returning. I’ve seen some houses where the roof had so much moss it grew into the gutters and the water seeped from the roof down into the side of the house causing thousands of dollars of costly repairs
Your roofs job is to keep water flowing off and away from your house.
Moss prevents this. Another way to think of it is how a river flows along unbothered and then a beaver builds a dam on it slowing the water down and causing a huge pond to build up. Moss is a similar dam concept.
Luckily it is pretty easy to remove and prevent.
How To Clean Moss off- the best way
My favorite method to get rid of loose moss is to use a gentle nylon brush. Brushing downwards and not using much pressure we can remove a large bulk of the moss while still maintaining the roof’s integrity and not damaging the asphalt shingles which is the most common type of roofing material.
Never use a pressure washer as this can cause serious damage if not used properly. Pressure washing is only needed for metal roofs or occasionally a concrete tile roof but I almost never recommend it unless you really know what you’re doing.
All we really need to do is brush most of the moss that comes off easily (anything that if you can kick and it falls off) and then we can chemically treat the rest.
There is some technique to this and I have some safety videos on my youtube.
Some additional tips are if you have a wood or tile roof just make sure you’re being extra cautious as those roofs can be slippery to walk on. Either use your safety rope and anchor or clean from the ladder using an extension pole.
Moss Treatment 101
Once you have as much moss as you can easily brush off it’s time to take care of the rest and prevent future moss growth.
I’m of the opinion that there are few ways to really prevent good old regular cleaning. You see certain solutions like gutter guards or zinc strips being sold that claim to “keep moss off your roof” or “never clean your gutters again when in reality neither of those are true.
zinc strips don’t work past a few feet- not a good idea
As long as there are trees and houses with moss near you, moss spores are constantly traveling through the air and landing on your roof. Nothing you can do about it.
But we can keep the environment up there toxic to moss and make sure no debris can build up there so that the moss can establish a foothold.
As such there are a few basic treatments if you want to read more in depth see How to Remove and Kill Roof Moss for Good but basically we can spray the roof with a bleach solution or apply a moss killer powder treatment.
With bleach we can either use oxygen or chlorine bleach. Most chlorine bleach at the store is around 6% strength of sodium hypochlorite so we just need to dilute that down to around 2-3% so you can use a pump sprayer and mix half bleach, half water, and then throw some dish soap in there as a surfactant (helps the chemical hold longer instead of evaporating off).
This is called soft washing and you will see professional roof cleaners use a larger spray tank on a bigger scale but a small sprayer will work just fine as it is very effective at killing the moss and especially if you only have small affected areas (typically the north side) sometimes you don’t need a full roof soft wash.
Moss powder treatments are usually either zinc sulfate (sold as moss out at Home depot) or almost any laundry detergent or cleaning powder such as borax or baking soda.
All of this stuff is toxic to moss.
You can apply it several times a year and watch everything slowly die and then just brush off the dead moss or wait for it to fall off. Typically though even if you do kill the moss there is still some manual removal involved.
Keep this in mind if you are cleaning your own roof or cleaning roofs for clients. The best results come from routine and regular maintenance. The easiest way to remove moss is by preventing a moss problem in the first place.
Anyways good luck, stay safe and keep them roofs clean!