On this page:
- Options and Cost Ranges
- Why Clean My Roof?
- Factors that Affect the Cost of Roof Cleaning
- What’s Involved?
- Getting Ready for Roof Cleaning
- Cost Comparisons
- Don’t DIY This One
- Find a Pro
Roof cleaning is a specialized service that removes stains and discoloration using landscape-safe detergents and low-pressure sprayers to distribute them. High-pressure washing may be more expedient and effective for metal or Spray Polyurethane Foam (SPF) roofs, which don’t have gaps through which the water can enter. Roof cleaning may also involve physically removing destructive moss and algae as well as installing zinc strips to prevent their return.
A dirty roof has a negative effect on your home’s curb appeal, but cleaning it isn’t just matter of aesthetics. Roof cleaning helps your roof last longer, can prevent leaks, and makes your house less interesting to animals seeking shelter. It also keeps your insurance company happy.
Options and Cost Ranges
Nationwide roof cleaning prices range from $350 to $1,200, depending on a number of factors, including size and pitch of the roof, type of service required and location. The cost can be higher if you go for installation of zinc strips to control algae growth.
A basic cleaning usually involves spraying detergents and eco-friendly bleaches on the roof at low pressures. If your roof is discolored but in good shape, this service is probably all it needs. Pros often estimate the cost by area, charging $15 to $30 per square. A square is an area equal to 100 square feet.
If your roof is made of an impermeable material that can’t blow back under high pressure, cleaners may use a power washer to remove mildew and algae. The advantage of this method is that it doesn’t use chemicals that could be harmful to surrounding vegetation. It costs about the same as low-pressure cleaning.
Moss and Algae Removal
Moss and algae can cause all kinds of roof problems, and to remove them, workers often kill them with a mixture of bleach and trisodium phosphate (TSP) before scraping them off. The cost of this service is commensurate with the amount of material that needs to be removed.
Installation of Zinc Strips
Installing zinc strips under the leading edges of roofing shingles and tiles prevents the growth of moss and algae and may be recommended by the cleaning contractor. A 50-foot roll costs between $25 and $50, and the cost of installing them depends on the characteristics of the roof.
Why Clean My Roof?
A Clean Roof Lasts Longer
Moss, mold and fungi feed on the organic material in asphalt shingles and if allowed to grow long enough, they can spread under shingles and tiles, and grow on the sheathing. As the sheathing rots, leaks and other roof problems can result. Cleaning the roof protects the roof covering and roof as a whole.
You’ll Save Energy
Organisms that grow on the roof absorb heat from sunlight and radiate the heat into the house, and you end up having to spend more to keep the house cool. A clean roof, on the other hand, reflects sunlight, so you don’t have to incur those extra expenses.
Animals Will Stay Away
Raccoons, squirrels and other pests that can make nests in your attic are actually attracted to the smell of rotting wood. According to the Northwest Landing Residential Owners Association, many animals associate the smell with the availability of food and shelter. Keeping your roof clean prevents rot and keeps the animals away.
Factors that Affect the Cost of Roof Cleaning
The size of the roof is an obvious determinant of the cost for cleaning it, but other factors, such as height and pitch, also affect the cost. It’s more dangerous to work on a steep roof, especially if it’s high and difficult to access, and special equipment, such as jacks or harnesses, may be needed.
A roof that has been stained by mold may need nothing more than a once-over with a low-pressure sprayer. This procedure rarely takes longer than a day. If the roof is covered with moss, the cleaners may have to apply a mixture of bleach and TSP and wait for the moss to die before scraping. This procedure may take two days. Add a third day for installation of zinc strips.
Many cleaners offer service with eco-friendly bleaches and detergents that won’t harm the surrounding landscape. These materials may add slightly to the cost of cleaning.
Cleaning the Roof Covering
One of the most common reasons to clean a roof is to remove darkening and discoloration caused by mildew. Many contractors use a special disk-shaped sprayer that can be dragged over the surface of the roof. The sprayer has no scrubbers or other abrasive components that can damage asphalt shingles or composite roofing.
Moss tends to grow on shady roofs, and it’s easier to remove if it’s dead. Workers kill it by spraying it with a mixture of bleach and TSP. After it turns brown, which takes about a week, they return with rakes and brooms to scrape it off.
Zinc Strip Installation
Zinc strips fit under the leading edges of the shingles and inhibit moss growth. To install them, the cleaners must lift the edges of the shingles, slide in the strips, nail them down and seal the nail heads with sealant. Installation takes two to three hours for an average-sized roof.
Gutter Cleaning and Shingle Repair
When the roof is dirty, there’s a good chance the gutters also need cleaning, and the cleaners may contract to do this for an additional price. If shingles have been damaged by moss and need to be replaced, the cleaner may also do this, for which there is also an extra charge.
Getting Ready for Roof Cleaning
The Pros Will Take Care of It
You don’t have to do much to prepare for roof cleaning unless you decide to do the job yourself, which isn’t recommended. Professional roof cleaners have all the equipment and supplies they need, and reputable firms can expertly access your roof and complete the cleaning procedure quickly and efficiently. You can, however, do a few things to make their job easier and protect your yard.
Clear Overgrown Vegetation
Trimming overgrowth around the perimeter of your house ensures the workers can safely place ladders where they need them. If they have to do the clearing themselves, they may add it to the bill, and they may not do as good a job as you would.
Cover Your Plants
Some of the chemicals used for roof cleaning can kill sensitive plants. Avoid damage by covering the plants with sheet plastic for the duration of the cleaning procedure.
Close the Windows
You don’t want the spray from the cleaning operation soaking your new bedspread, so make sure all the upstairs windows are closed. It’s not a bad idea to close the downstairs windows as well.
|$300 - $600||$350 - $1,200||$900 - $2,000|
Cleaning costs vary with roof area. In this example, we list the costs associated with a 2,000 square-foot roof.
Washing Only: $300-$600
- • Budget Service: Your cleaning firm may decide to pressure-wash your metal or SPF roof. This service is usually the least expensive.
- • Basic Service: The most basic cleaning service involves washing off mold and discoloration with eco-friendly detergent. Many firms charge a flat rate of $350 for this service.
- • Enhanced Service: Whenever conditions for workers are hazardous, you can expect to pay more for cleaning services.
Washing with Moss Removal: $350-$1,200
- • Budget Service: If moss growth is not extensive, cleaners may be able to handle it by adding bleach and TSP to the cleaning solution. In that case, the job won’t cost much more than a basic cleaning.
- • Basic Service: Moss growth may be limited to small sections of the roof. The extra cost is commensurate with the time required to remove it.
- • Enhanced Service: When moss covers the roof, it may have to be treated and scraped off before the roof can be washed. The procedure may take two or three days, and the cost can rise to $1,200 or more.
Washing, Moss Removal, Repair and Prevention: $900-$2,000
- • Budget Service: Cleaners spray moss with a bleach/TSP solution to kill it, then scrape it off using roof rakes or brushes. Low-pressure spray is used to remove blackening due to mold and mildew.
- • Basic Service: After moss removal and cleaning are completed, and the roof has dried, shingles damaged by moss are replaced. This cost estimate assumes less than 10% of the shingles are damaged.
- • Enhanced Service: In addition to cleaning and repair, workers install zinc strips under the shingles to prevent moss growth and extend the life of the roof.
Don’t DIY This One
Roof cleaning isn’t a job homeowners should normally do themselves. One reason is that working on a wet roof can be dangerous -- especially if the roof is steep or high. Another is that the job requires specialized equipment that can be heavy and difficult to transport to the roof. A third reason is that professionals can assess the condition of the roof and offer valuable advice to help you keep it in tip-top shape.
Roof Cleaning Services
If you’re tired of looking at your blackened roof, or you think it’s time to remove those clumps of moss, it’s time to call in the roof cleaning pros. Because contractors may differ on the treatment your roof needs, be sure to get more than one assessment. Comparing quotes is also the best way to ensure you get the best value for your money.