Roof cleaning: what to know

What the job involves, what changes the price, and what to ask a pro.

What roof cleaning is

Roof cleaning removes moss, algae, lichen and debris from shingles, tile or metal, using low pressure and a cleaner suited to the roofing material. People call when dark streaks, green growth or moss has built up, and they want the roof protected and the plants around the house kept safe.

Signs you need it

  • Dark streaks running down the roof from ridge to eave, which are often algae
  • Green or black moss clumps that hold water against shingles or tile
  • Gray or orange lichen crusts on tile or shingles
  • Granules in the gutters beyond normal wear, with shingles that look dull after growth has been there a while
  • Leaves and pine needles stuck in valleys and behind chimneys, staying wet and feeding growth

What the pro does

  • Walk the roof and the yard to identify the roofing material, its condition, and what the growth is
  • Protect plants, siding, windows and entry points with covers, then wet down the plants before any cleaner is applied
  • Apply a moss and algae cleaner suited to the roofing material, and let it dwell for the time the product label gives
  • Remove loose moss and debris with a soft brush, working from the top of the roof down so debris is not pushed under the shingles
  • Rinse with low-pressure water, then check the roof for lifted shingles or cracked tile and note any repairs needed

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Roof size, pitch and access, including single-story and steep roofs that need extra fall protection
  • Roofing material, since asphalt shingles, tile and metal each need a different method and product
  • Amount of moss, algae or lichen, and how long it has been growing
  • Whether an anti-growth treatment or zinc strips are added, since they are extra material and labor
  • Plant and landscape protection needed around the house
  • Whether gutter cleaning is added to the visit
  • Repairs found during the wash, such as lifted shingles or cracked tile

What a written quote should spell out

  • Roofing material and the cleaning method used for that surface
  • Cleaner product name and how it is applied, plus the rinse method
  • Plant and surface protection steps, such as covers, wet-down and rinse
  • Anti-growth treatment, including any zinc strip installation, shown as its own line
  • Whether gutters are cleaned and whether debris is removed from the roof and yard
  • A list of damaged shingles or flashing found during the cleaning, with photos

Questions to ask before you hire

  • What cleaner do you use on my roofing material, and is it safe for shingles or tile?
  • How do you protect my plants, siding, windows and landscaping from the cleaner?
  • Will you use low pressure or high pressure on my roof, and why?
  • Do you offer an anti-growth treatment, and how do you explain how long it lasts?
  • Will you check the roof for lifted shingles or cracked tile during the wash?
  • Who is on the roof, and what fall protection do they use on this pitch?
  • Can you send a current insurance certificate that covers roof work?

Red flags

  • High-pressure washing on asphalt shingles or tile, which strips granules and cracks tile
  • No plan for plant protection or for where the cleaner runoff will go
  • Cleaning done from a ladder onto a steep roof with no fall protection
  • A promise that the moss will never return, with no description of the treatment
  • Moss scraped or raked off dry with a metal tool, which tears granules off shingles

What you can do yourself

You can safely trim tree limbs that overhang the roof from the ground with a pole saw, and clear leaves from gutters and valleys you can reach from the ground. Do not climb onto the roof to scrub it, and do not use a pressure washer on shingles or tile, since that strips the surface. Call a pro for roof cleaning, especially on steep or tall roofs or when the growth is heavy.

Licenses and permits

Roof cleaning alone is commonly offered by exterior cleaning companies, and licensing rules differ by place. Check with your state and local licensing agency to confirm what applies, and check roofing licensing rules for any repair work done during a cleaning visit.

Roof cleaning questions

Will roof cleaning damage my shingles?

It can, if the wrong method or pressure is used. A pro should use low pressure and a cleaner suited to your material, and explain the method before the work starts.

Does moss come back after cleaning?

It can. An anti-growth treatment or zinc strips slow regrowth but do not stop it entirely. Ask the pro how the treatment is applied and how they will check it.

Is roof cleaning the same as gutter cleaning?

No. Roof cleaning removes growth from the roof surface, and gutter cleaning clears debris from the troughs. Many pros do both in one visit, but ask whether each is included.

Will the cleaner harm my plants?

It can, if plants are not protected. Ask the crew how they cover and wet down plants, and how they rinse the surfaces near beds and the lawn.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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