Ah, the Pacific Northwet. Where every day it rains and supplies the perfect breeding ground for the green botanical goblins that abound on every tree, rock, and (hopefully not yours!) roof.
But don’t worry, moss on your roof can be dealt with just like any other home maintenance project.
Removing and preventing moss from being on your roof can not only extend the life of your roof, but it just plain looks nicer and makes your home look more taken care of. Not to mention a much higher ‘curb appeal’. Add to the fact that when left unchecked, moss can subtract 5-10+ years off of your roof life.
Even if you’re not trying to sell your house, moss is easiest to stop before it even gets started. The longer it grows the worse it’s going to get.
Why Moss Grows On Roofs
Moss floats around on spores that perpetually rain from the sky from trees and other roofs. It’s pretty much inescapable if you have any trees around you.
Moss also loves structure or anyway it can get a foothold on a roof. This means any leaves, needles, or other debris can host moss and help it get established.
It also thrives in the shade. Whether this is from trees or debris, you can definitely expect most of the moss to grow on the north-facing side or anywhere under trees.
Therefore, one of the biggest steps you can start with is to remove any trees growing directly over your roof. This isn’t always practical, but you should at least trim the most egregious branches that shade your roof and provide debris for moss to get established on.
Moss Removal From Your Roof
Now to getting rid of the green stuff for good! Where we live and work in Seattle, there are two methods we recommend removing moss from your roof.
The fast and slow.
The Easiest (but slowest) Method To Remove Moss
The slow way to do it is to get some of the moss-out powder and generously coat any moss growing on your roof. This usually only works if the moss isn’t too large or thick yet. If it looks more like a 2-inch shag carpet, you’ll probably want to get up there with a brush or hire a professional to come get it done.
To apply the powder, put more around the peaks and top of the roof. As it rains, it will slowly wash down over the next few weeks. If you’re in the Seattle or surrounding Western Washington areas, it’s probably raining right now. If it is raining that’s fine, just be careful up on the roof but you can still apply the powder.
Once applied, read the packaging label, it usually states that it takes several weeks to take effect, so you can usually expect to wait at least 1-2 months to start seeing dead moss.
At this point, you can keep reapplying if you still see green moss. But if it’s all dead and blacker in color you should be able to rinse it off with a standard garden hose. Never use high pressure like a pressure washer unless you’re really experienced and know what you’re doing and don’t mind risking the integrity of the shingles.
This method can take a month or two but generally, it can have success as long as there wasn’t too much moss, to begin with.
If you’re looking up at your roof and you see quite a bit more moss and it looks more like this then you should try out the fast (but far more work) method.
Cleaning Moss Off Your Roof the Fast Way
This moss needs to be physically removed. Use a nylon brush or something with stiff enough bristles to push off the moss. You don’t want it too strong to damage the shingles, however. I once saw a guy use a wire brush, nothing could be worse for your roof! Use gentler brushes than that.
Make sure when you’re on the roof you are being safe and roped up. Moss can be very slippery, one slip and you can be done for. Be safe!
Once upon the roof, you want to gently brush off the biggest and baddest clumps. You don’t need to get every bit of it, but shoot to remove at least 90% of the growth.
For a standard roof, cleaning will usually take 4-6+ man-hours to get done. Our exact process is labeled here. Once all the moss is removed it’s usually a good idea to do an extra treatment. This is a soap/water/bleach mix that is gently sprayed onto the roof to kill any extra bits of moss.
Just before spraying, always clean out the gutters as well. A good gutter cleaning is something we do every time we have a job in our local area of Seattle. We’ll go more into gutter cleaning in another article but it can be equally important to keep your house and foundation free of water.
Spraying Your Roof
I use a big 26-gallon pump sprayer but you can also get the 2-gallon hand sprayers if you want to do it by hand. The Asphalt Roofing Manufacturers Association (ARMA) recommends a 1:1 ratio of bleach to water. I’ve found that to be a bit overkill, in general, you should have around 1-gallon of bleach for every 5 gallons of water. This can vary based on how much moss is left over. When you spray you should see any bits of moss turn white/yellow very quickly.
At this point, once the roof is completely cleaned and washed and the gutters are cleaned it’s a good idea to still apply the moss b ware powder. If you don’t have a sprayer or don’t want to mess with it you can definitely just apply extra powder. This won’t do quite as good of a job at getting in between every little crack the moss is in but it works well enough.
There you have it. If done properly you may have just bought yourself another 5-10+ years of a nice clean roof. Just remember to re-apply moss out/moss b ware powder every year or so and clean out the gutters as needed.
Let Us Know If You Need A Hand
If you live in Seattle, Ballard, Bellevue, Redmond, Sammamish, Bothell, Lynnwood, Edmonds, Renton, Burien, Issaquah, Mercer Island, Shoreline, Kirkland or anywhere near any of these cities, we invite you to give us a call or text if you have any questions about cleaning your roof or to get a free quote/estimate – (360) 917-5596
Thank you, and have a great day!