Roof cleaning guides
A good roof cleaning project runs in four steps: identify what is growing, choose the method (soft washing for asphalt shingles, per ARMA), hire and verify a properly insured contractor, and then reduce recurrence by trimming branches and considering zinc or copper strips. Skipping step two is what damages roofs.
Identify. Photograph the roof from the ground on each elevation. Moss is green and three-dimensional. Algae is flat black streaking, most often gloeocapsa magma per ARMA. Lichen looks like crusty patches bonded to the surface. Knowing which you have sets both urgency and price.
Choose the method. For asphalt shingles the answer is soft washing. ARMA's guidance is a cleaning solution applied, allowed to dwell 15 to 20 minutes, and rinsed thoroughly with low-pressure water - and never a pressure washer, brush, or broom. Get this in the contract, not just in conversation.
Hire. Verify liability and workers' compensation insurance directly from the insurance agency. Ask what fall protection the crew uses. Confirm landscape protection is in scope, since ARMA advises protecting landscaping and surrounding areas from the bleach solution. Sanity-check the price against Today's Homeowner's $255-$1,190 typical range.
Prevent. ARMA is clear that cleaning is temporary. The durable levers are trimming overhanging branches so sunlight and airflow reach the roof, keeping debris off, and metal ion sources - zinc or copper strips, which Malarkey notes work best installed at new roof installation, or algae-resistant shingles at your next re-roof.
Choosing roof cleaning an approach
The judgement calls that decide the bill, before anyone quotes you.
- Do the identification step yourself Ten minutes with a camera from the ground. It stops you being sold a moss-removal price for an algae-staining problem.
- Put the method in the contract "Soft wash only; no high-pressure equipment on the roof surface." That sentence is your recourse if granules end up in the gutter.
- Verify insurance before scheduling, not on the day Certificate direct from the insurance agency. On the day, you are already committed.
- Trim the branches - it is the highest-return step Shade and debris are the cause. A tree trim reduces every future cleaning and every future moss problem.
- Plan algae resistance into your next roof ARMA notes algae-resistant products are commercially available and designed to inhibit growth for extended periods. That is a specification decision at re-roof time, and it costs far less than repeated cleaning.
All roof cleaning guides
Roof Cleaning Planning Guide
Soft Wash Roof Cleaning Guide
Roof Moss Removal Guide
Roof Algae Stain Guide
Roof Cleaning Safety Guide
Hiring a Roof Cleaning Company
Roof Cleaning and Manufacturer Warranties
Climate and Roof Growth Guide
Roof Maintenance After Cleaning
When Cleaning Is Not Enough
Cross Link to Full Roof Replacement Path
Seasonal Roof Care Guide
Where these figures come from
Sources last checked
- ARMA - Algae & Moss Prevention and Cleaning for Asphalt Roofing Systems · retrieved 2026-07-25
- Malarkey Roofing Products - Managing Moss and Algae on the Modern Roof · retrieved 2026-07-25
- Today's Homeowner - How Much Does Roof Cleaning Cost? (2026) · retrieved 2026-07-25
You know more than the last homeowner they quoted.
That is worth something only while you are still choosing. Tell us what is going on and we will match you with a few roof cleaning pros whose licence and insurance we have already checked - free, no obligation.
Free · No pressure · Only your matched pros get your details