A clean roof not only makes a house look better, but it can also extend the lifetime of the roof and enhance the home’s value. Removing heat-insulating mold and algae makes a roof more energy-efficient in the summer too. Most roof cleaners will want to see the roof before providing an estimate to more accurately understand the job. Generally speaking, the more difficult it is for a professional to get a roof clean, the more it will cost. Other factors include the size of the roof, how long it’s been since it was last cleaned, and the location and height of the roof.

Size

The size of roof usually directly correlates to how long it will take to clean and, thus, how much it will cost. The larger the roof, the higher the price. Many roof cleaners charge by the square foot, and others charge by the square, which is equal to 100 square feet.

Time since last cleaning

The longer it’s been since a roof was last cleaned or the dirtier it is (for any reason), the longer it will take to clean. The overall cost is likely to be higher.

Type of cleaning

Roof cleaners take numerous approaches. In rough ascending order of cost, methods include chlorine bleach, pressure washing (both not recommended since they can damage the roof), low-pressure washing, and a hose and nylon brush. The type of roof can determine the type of cleaning used. Asphalt, ceramic tile, clay tile, concrete tile, slate, tar and gravel, and wood all require different cleaning methods.

Complexity and time spent

Not surprisingly, the more complex roof is, the longer it will take to clean and the higher the cost. For example, roofs with hip sections—slopes on all four sides—and those with obstructions such as chimneys, trees and decks will cost more to clean.

Pitch/slope

Roofs with steeper slopes are more dangerous for the cleaners, so safety precautions and staging may have to be added. These conditions will increase labor and overall costs.

Location

The roofs of homes at the beach or in the mountains are affected by weather and atmosphere and can be more dirty than in other areas. Roof cleaners may charge more because it will take longer to clean a roof in these locations. If there’s a lot of salt, moss or algae on a roof, the price will be higher for cleaning because those substances are more stubborn to remove.

Height

The more stories a home has, the more difficult it is for cleaners to maneuver their personnel and equipment to clean a roof effectively. So the taller the building, the more expensive the cleaning services.

Additional services

Upon request, many cleaners can apply zinc strips or anti-growth sprays to protect a roof until the next cleaning. These services cost extra. Most cleaners charge under $50 per zinc strip plus installation, for example.

Cost-saving strategies

Some roof cleaning companies offer discounts if customers get on a regular cleaning schedule, such as once or twice a year. Some roof cleaning companies also offer to clean gutters, so you may be able to get a discount if you combine the two services.