Cedar Roof Cleaning 101

I have a customer with a 10k sq ft cedar roof… HEAVILY infested with everything you could imagine that would grow on the roof. To the customer, cost isn’t the issue. First things first… let’s talk chemicals and cleaning methods.

I have done tons of research, seen what Sullivan does on his roofs (great work), watched videos, read articles about cedar. I don’t want to use SH on the roof since I don’t want to bleach the shingles and def do not want to put pressure on it. I want to clean the shingles with chemicals and water pressure. I can get industrial TSP (Trisodium phosphate), Sodium Percarb, and Sodium Hydroxide from my supplier. I totally agree with Sullivan on not putting pressure on the roof and instead, use your 12v to apply chem AND rinse with water. I will be using ladder stand off’s (dont’ know what they’re called) so I can lean to the roof and not walk on it. Shingles can compromise if you don’t lift your foot when you turn, cedar can snap or worse if you aren’t careful. My goal is to mix my powders at the proper ratios and wash with my mix. I know Percarb is good for roofs like this, but just want to make sure that someone out there may be able to guide me a bit more as far as ratios, chemicals, and methods. Also, I want to do a brightener with oxalic acid after cleaning. Using an oil seems to not be necessary since the oil may or may not soak in, and probably doesn’t extend the life of the roof any. I may be making this a bit harder than what it is, but I really want to do a good job for this customer. Especially if I’m charging around $.80 a sq ft because of the infestation. Thank you all for your knowledge and support. Look forward to hearing from you.


Who is Sullivan?

He’s a member here. Has a cedar roof cleaning business and YouTube videos. Bruce Sullivan.

Tag him. Just use the @ symbol before his name on here.



Thanks for the tip, had no idea how to do that.

1 Like

Got any pics?

I’ll have to look back through, but I don’t think that I got any. I never planned on posting this. It’s just heavy infestation with lychen, moss, and black mildew. The moss infestation is pretty bad since a good bit of the house has some tree cover. It def isn’t good. I am prepared for the roof to take two to three washes given the situation, but want to make sure I’m using the correct chemicals and charging correctly. Cedar is a bit hardier than pine (used on decks), so I imagine any deck washing methods would suffice for the cedar too, but not using pressure? I’ll post what I did and how I did it on this thread when/ if the bid get approved. I also plan on putting a YouTube video up if time allows.

I think that good hard workers avoid work in fear of messing something up or not knowing where to research stuff. The thing is that if you’re a good contractor, you’re the best chance the homeowner has at getting something done without messing stuff up. They could be dooped into someone stealing money or someone saying they know what they’re doing but don’t. So if the information found here can help both a contractor and their customers, I’m in.

Any suggestions? I’m meeting with the guy next week. He asked how necessary it was to have it washed so I’m bringing him pictures of before and after and what it’ll do to the shingles if it stays on there. I guess at the price, I aught to bring him a steak dinner too.

So Sullivan has a system with proprietory chemicals he uses. He charges (last time i inquiered about $3000 usd) to buy into his system and referral network. You wont know his sistem unless you buy i or someone that bought into it tells you.

You can always use sodium percarbonate, low pressure rinse (1000 psi or less) and add some oxalic acid to brighten if youd like. You can also replace percarbonate and use hypochlorite using same steps.

You can use pre made cedar roof cleaners but you still have to low pressure rinse and it costs way more than buying percarbonate in bulk

Also i forgot to mention… if you hve lots of pine needles, moss, etc youre going to have to remove it first (leaf blowing, brushing, even heard you can use air pumps to blow them out even better)… also you better be comfortable walking on cedar shake roofs and buying good anchor + korkers with the right cleats or else book a room at your nearest hospital or funeral home lol

Figure out how many squares it is, then call the largest reputable roofing company in your area and get a price for replacing cedar shake roof. Most will gladly give you a ballpark figure. Then price it at about 10-15% of that. Don’t be shy on the pricing. Once you get that quote from roofing company, you know he’ll be ecstatic with your price, because he’s probably already checked too.

Ahh! You guys are awesome. I gave him $0.90 a square foot, he said is it necessary. I said, well… yes… I’m meeting with him Wednesday of next week to show what it’ll look like after, vs how it looks now. Also I’ll show him how that mess eats his roof.

Thank you so much for your input about the products and methods. I will probably go percarb (55lb bag here is 75 bucks) and wash that way, given he says yes. I have cougar paws and a ridge pro. Are there better options than those for walking cedar? I just called and booked a room at the hospital :joy::rofl:

I do roofing contracting as well, but know only shingle, and have guys that do metal and metal shake, but don’t know any cedar or slate roofers. I was going through Buckhead one day and almost stopped to get the roofers number. Lol. That’s a really great idea though, get a percentage of replacement. That’s going to be for the next job. I’ll keep y’all updated!

for walking on cedar roofs, check out: TuffTrax | Work Boots | Korkers

I’m up in the PNW and have had to deal with cedar roofs a ton. Be SUPER careful when they’re covered in algae and are wet. They are absolutely slicker than you might think.

The spiked Korkers help a ton, just make sure to use fall protection if you’re getting up on the roof. I had a slip a few years back while wearing the spiked korkers and ended up with my feet overhanging the edge of a 3 story roof (caught by my rope setup). I had knelt down to move my rope around a ridge cap and started to slide. No amount of grabbing could stop me, so I enjoyed the ride and prayed my rope set up was sufficient. Fortunately it was.

All that to say, be careful out there!


Edit: Just saw this was from a year ago…haha, oh well. advice stands nonetheless

1 Like

Any updates on this job? I am interested and would like to see how it went. Thank you @A.M.P.W

can you share how you put an anchor on a cedar roof?

Hey Chris;

Wish I could give you a one-size-fits-all solution but honestly for me it changes on every roof. Before roof cleaning I spent about 5 years working in Rock Climbing gyms so i already had a pretty good knowledge or rope/anchoring systems.

anyways, Here’s my normal breakdown though and what I try and consider when setting up a roof anchor system. (Also note, this is just from my experience…obviously am in no way telling you what you should/shouldn’t do)

First my gear: I typically carry a 50’, 100’, and 150’ static rope. (You don’t want a dynamic rope, as they stretch and could lead to an accidental fall). I also use a petzl fall arrest harness and a shock absorbing lanyard. Those are the basics, then you’ve got all the carabiners and other gear.

For a basic set up, on a cedar roof, the first thing i look for is obvious anchor points. Engineered anchors and strong chimney are the main ones here. If there is something i can toss the rope around and clip into, then perfect; hook up and go.

From there, it’s honestly 99% doable with ground anchors. I’ll toss the 150’ rope over the roof and look for anything ground level i can anchor to: My work truck, trees, fence posts, etc. I would then tighten up the rope, tie a Butterfly loop (Butterfly loop - Wikipedia) or Figure 8 knot up at the peak, clip in with my shorter rope and use that for the job.

In rare cases (maybe twice in 10 years) i’ve also used ground anchors (Similar to this: 1" x 8" x 66" Helical Auger Anchor - 11000 lbs Max Capacity) when there was nothing else around.

a good rope set up with the addition of spiked shoes makes working on a cedar roof totally safe.

However, like i said, i’ve got lots of experience with rope set ups and you absolutely need to know your own personal limitations.

I could probably go on about this forever but i feel like that gives a fairly decent summary


Well, I sat him down, gave him the price and the conversation went something like this. Me, " I think you need to have this cleaned because if you don’t you’re asking for the rest of the roof to rot and that will give your interior a ton of water intrusion."
Him, " I’m old… I’m 76. I don’t have a ton of time left, I don’t have a ton of time left in this house. Do you think I need a new roof instead of cleaning?"
Me, " Yes. It’s terrible up there. I can repair small stuff, but the roofing system below the shakes is completely compromised in multiple spots and I’m not equipped to handle that."
Him, "Do you think that if I was to replace the roof, incur the cost, stay here for another 5 years, give the property to my kids to tear down, would it be worth it?
Me, “…no… Your house is massive. Thats a huge job and very expensive. Try to insurance claim the job, if you cant, replace with asphalt if you don’t care to keep the cedar knowing your kids will tear down the house, but if you want your roof to stop falling apart, repairs and cleaning are in order.”
Him, "It’s lasted me over 30 years, and if it’s good for another 5 years, I just don’t care that much.
Me, “I’ll wash your house and you decide what you want to do with the roof”.

Needless to say, I haven’t done the roof yet but even if I do, I’ll have to get a company out there to do some big repairs. There were multiple points that didn’t need just a shingle or shake, it needed a full replacement. At some point someone feathered an asphalt roof on a slope to the ridge of cedar… don’t know how that works out. I do all his washing, but I really don’t think he wants to pay 10k+ to wash the roof. I’ll update if I get another roof with my mixtures and everything.

1 Like

Dude you gave great info! That anchor you used one (pain in the butt to dig down) is used and is a standard code for strapping down mobile homes, so I think if someone yeeted themselves off a roof they’d be okay :rofl: I’ll be writing back in if I find any other shakes, but mostly around me is asphalt and slate. Also, good info on your knots. Too many people don’t know what all to do with them. When it’s life safety “if you can’t tie a knot, tie a lot” doesn’t really apply. I use a ridge pro, but if the ridge is compromised, I have to drill into the sheething or roof trusses, but only ran into that once and just readjusted the anchor. Thanks for the info on the boots too!

Glad you’re doing it right! I see way too many guys up on youtube and other places who don’t even think about fall protection. Kinda crazy!