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Process of Pressure Washing a Roof | Your How-To Guide

November 20, 2020

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If you’re a homeowner searching, “How do you pressure wash a roof,” you’ve come to the right place! This handy how-to guide will give you all the tips needed for safe, effective roof washing, as well as some common mistakes to avoid along the way.

Before we begin, remember that safety always comes first and especially when working on a roof. Invest in boots with thick but soft rubber tread, as hard plastic tread can strip granules off shingles and loosen shingles and tiles. You’ll also need eye protection, thick work gloves, cotton pants and a cotton shirt with long sleeves, to protect your skin while working. Ensure there is no one underneath your work area as well, so they’re protected from running water and dropped tools!

How Do You Pressure Wash a Roof? Getting Started

First check out some quick reminders for getting started with safe, effective roof washing for your home:

  • Note that you might need different pressure washing nozzles and cleansers for your home’s roof. Some cleansers are designed to kill growing moss, mildew, algae, and mold, while others are designed to dissolve thick dirt and soot.
  • High-pressure washing is not usually needed for removing everyday leaves, twigs, bird’s nests, and storm debris; a standard garden hose is often sufficient for general cleaning. Start with a hose and note if this gets your roof as clean as expected, and then move on to power washing equipment if necessary.
  • Always start power washing a roof with the lowest pressure setting on your equipment, to avoid stripping granules from shingles or blowing shingles right off the roof!
  • Start from the top of the roof or its pitch and work your way down, rather than using high pressure along shingle edges and pushing them up, as this can actually pull shingles off the roof.
  • Work in small sections so you can rinse detergent away quickly. Dried cleansers tend to leave behind unsightly streaks and sticky residues that attract more dirt than before!
  • Working in small sections also allows you to stay on dry areas of the roof, reducing the risk of slipping and falling.
  • Always keep the pressure washing wand moving from side to side so that you don’t loosen shingles, tiles, nails, flashing, or other materials, or cause them to split and crack! If you cannot loosen and remove certain dirt or grime, try another cleanser, not higher pressure.
  • Stop often as you work, checking to ensure you’ve removed all dirt and debris. Your power washing work might loosen some hidden dirt and residues, so you’ll want to check that you’ve done a thorough job before moving on to another roof section or wrapping up your equipment for the day!
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What is the Best Way to Clean a Roof?

Now that you’ve reviewed some tips to help you get started power washing a roof, let’s move on to the actual power washing process. Start with a 35-degree spray nozzle and detergent needed for the cleaning at hand, whether that’s dirt, mold, algae, or other residues.

To scale the roof, position a ladder against a section you can climb without damaging gutters, eaves, and other obstructions. Start washing at the top of the roof, cleaning shingles in a downward motion, sweeping the wand side to side. If you see granules or bits of grit coming loose from the shingles or notice any in the gutters below, lower the pressure on the washing wand.

For black mold, apply the cleanser and let it sit for several minutes so that it can kill and dissolve spores, but don’t allow it to dry. Apply more cleanser as needed but rinse that detergent away once you see mold spores coming loose.

As you work your way down the roof, use caution every time you take a step forward. Ensure you have a firm foothold and stop your forward motion if you feel yourself slipping. Remember that you can always go back and rewash your roof if needed, but falling from the roof can mean serious injury and even death, so work slowly and never overlook safety while washing a roof.

The BEST Way to Clean Moss Off the Roof

Never ignore green moss growing on a home’s roof! While this growth might look rustic and casual, that moss leads to water damage and lost shingles and tiles. To clean moss off a roof, start with a hose, rinsing away as much loose vegetation as possible as well as other dirt and debris.

Next, use a soft-bristled roof brush to gently scrub away as much moss as possible. Ensure you choose a roof brush and not an outdoor brush meant for concrete, pool decks, and other surfaces, as tough rubber bristles might strip shingles granules and loosen shingles, tiles, and flashing.

If there is still moss on the roof, invest in a roof cleaner meant to kill moss, mold, algae, mildew, and other such vegetation. Wait for a cloudy day to apply the cleaner so that it doesn’t evaporate in hot summer sun. After application, a simple rinse is typically all that’s needed to remove remaining moss and other residues.

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Will Bleach Damage Shingles?

Bleach is often used to kill mold and mildew, but note that bleach won’t brighten a roof the way it does clothing! Chlorine bleach brightens clothes by removing inks in fabric dyes but it doesn’t have that same effect on asphalt shingles.

Many homeowners and pressure washing contractors note that diluted bleach is typically safe for a home’s roof. Mix a cup of chlorine bleach into a gallon of water and try this solution on an obscured part of your home’s roof, noting if it offers the cleaning you need without causing shingle damage. If so, you can typically use the same solution on your home’s roofing shingles without drying them out or causing other damage.

Understanding Different Pressure Washer Roof Cleaning Attachments

First note that some pressure washer equipment attachments are brand specific, meaning that they only fit their brand and not all power washing wands on the market! For a roof, invest in a pressure regulator, to monitor water pressure as you work. Added control over water pressure reduces the risk of stripping granules and pulling up shingles, nails, tiles, and flashing.

Telescoping or extension wands are also excellent pressure washing roof cleaning attachments, as they allow you to reach many areas of the roof while staying safely on the ground or ladder. You can also use these to reach areas around the chimney, vents, and other obstructions, with far less climbing and clambering over those areas!

Nozzles for your pressure washing wand typically use a universal color coding, to designate various degrees. A red, 0-degree nozzle uses the highest concentration of water spray, while a white, 40-degree nozzle and black soap nozzle offer the widest spray and lowest pressure. For washing thick dirt and grime from roofs, use nothing lower than a yellow, 15-degree nozzle.

Is Roof Cleaning Necessary?

If you’re like many homeowners, you probably rarely even look at your home’s roof and easily ignore dirt and grime. Pressure washing a roof is also a big job and can also be messy and cumbersome. Since it’s difficult to pressure wash a roof, you might wonder, is roof cleaning necessary?

While a home’s roof might be the last thing you think about when it comes time to clean, keep in mind that dirt, soot, air pollution residues, and dried dust can dry out shingles and tiles, leading to premature cracking and other damage. Leaves, moss and mold, and storm residues all hold moisture against the roof, even working their way underneath tiles, which increases the risk of water damage!

No matter the cost of roof washing or how cumbersome the job, it’s vital that homeowners schedule this work as needed, usually every two to three years. Consider annual roof cleaning for homes in tropical areas or those located near busy roadways and airports, which are usually coated with more gritty debris as well as drying soot and pollutants. No matter your roof washing cost, consider that it’s far cheaper than having to repair that roof and replace tiles damaged by dirt and debris!

How Much Does Roof Cleaning Cost?

Most pressure washing contractors charge by the square footage, and might adjust that price for especially dirty roofs or those with lots of obstructions such as dormers and skylights. Most homeowners should expect to pay between $.20 and $.60 per square foot, or $250 to $450 in total; average roof cleaning costs range about $350 to $400.

In some cases, a power washing company might offer discounts if you “double-up” on power washing services. Gutter cleaning is as vital as roof washing, for instance, as gutters direct rainwater away from the home and to nearby downspouts. When asking about roof washing, ask your contractor if you might also schedule gutter cleaning, window washing, exterior wall washing, and other such services, to protect every surface of your home from damage and potentially save some money on all those services overall!

A Word from ProClean Pressure Washing Venice

This information is proudly presented to you by ProClean Pressure Washing Venice. If you’re in the Venice, Florida, area and still find yourself asking, “How do I pressure wash a roof,” or need high-quality Venice soft wash roof cleaning, call the most trusted name in the industry, ProClean Pressure Washing Venice! We have over 20 years of industry experience and guarantee satisfaction with every job.

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