Two to several hours, depending on how dirty your roof is.
Cost
$25–50
Just a short shopping trip (or online order).
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What you'll need:
TOOLS
Shoes with good traction
Eye protection
Gloves
Soft cloths
Sponges
Soft-bristle brushes
Non-abrasive pads
Garden hose
Bucket
Tarps (optional)
SUPPLIES
Water
Dish soap
Gentle cleaning mix
Like any part of a home, metal roofs need regular maintenance, and a good cleaning will extend the life of metal roofing and keep it looking its best. Periodic cleaning removes dirt, leaves, pollen, stains, and spores. A deep cleaning for metal roofs every two to three years is ideal, but an annual light cleaning is a good idea. This guide will walk you through how to clean a metal roof.
Preparing to Wash Your Metal Roof
Only take on a DIY job like this if you feel safe doing so. Working on a ladder and getting up on a roof always presents the risk of serious injury. If you aren’t physically comfortable with all components of the task, it is probably best to hire a roof cleaning contractor near you. This is the best way to ensure the job gets done safely, correctly, and with no danger to you. The following steps detail how an experienced DIYer or a roofing pro would clean a metal roof.
Take the Proper Safety Precautions
Even single-story roofs are high enough for fatal falls, and wet metal roofing is very slippery. Because this project involves ladders, heights, slippery surfaces, and chemicals, plan carefully before beginning and stay alert to possible dangers during the work. Here are some safety precautions you should consider:
Know what coatings or sealants are on your roof and what cleaning methods are manufacturer approved. Cleaning a metal roof with chemicals or walking on it may invalidate your warranty, so be sure you know what’s allowed.
Wait for a dry, cool, cloudy, and calm day so you’re working in the best possible conditions.
Only clean areas you can safely reach.
Use eye protection and gloves when working with chemicals.
Only use an OSHA-approved ladder, and consider using a harness or other fall protection.
Wear shoes that offer good traction.
Read the use instructions for all chemicals and equipment, and be sure you understand and follow all recommendations.
Cover landscaping with a tarp or plastic sheeting to prevent damage.
Bring a Friend
Never get up on your roof alone; always have at least one other person actively assisting you. This person should be willing and able to help you safely climb the ladder, assist you with chemicals and equipment, and monitor the safety situation from the ground. They should know the plan and be able to assist if something goes wrong or call for help in case of an emergency.
Create a Plan
Start by walking and talking through the plan. This includes walking through the entire job from start to finish and double-checking that you have all the needed equipment and materials ready. This is also your chance to perform a safety assessment of the roof. Decide where you’ll walk and stand and look for potential hazards and parts of the roof that you need to avoid. Ensure your helper knows their role and what you’ll rely on them to do.
Clean the Debris
Photo: AscentXmedia / E+ / Getty Images
Remove sticks, leaves, and other loose materials before using water or chemicals. Use your hands, a leaf blower, or other tools to free debris from the gutters and roof.
Move to a Safe Area Before Utilizing Any Liquid
Wet metal roofing is slippery and dangerous. Therefore, it’s absolutely critical that you never walk on wet areas of the roof. Plan to stand on a dry, higher vantage point and spray water away from you and down the roof to clean away dust, debris, and dirt.
Always spray from the top down. Spraying up from the ground can push dirt and debris higher up on the roof and make a bigger mess. Most DIYers use a garden hose and plain water for this task, but if your roof is very dirty and you have experience with this project, you may choose to use cleansers or chemicals. Take your time during this phase, as it’s the main portion of the job.
Note: As tempting as it may be, don’t use pressure sprayers on metal roofing. High pressure can dent and damage metal roofs, and it can remove specialty coatings. Pressure washers are also very heavy and hard to maneuver, and they can cause scratches and dents. Instead, try a gentle-but-effective mixture of ¼ c dish soap, laundry detergent, or car-wash soap per 1 gallon of water.
Scrub Any Remaining Dirty Spots
Once you’ve gone over the roof once, let it completely dry. This will allow you to see the remaining dirt and make it safer for you to move on the dry roof. Locate and have your on-the-ground spotter make a note of areas that need spot cleaning. Then, individually address each remaining dirty area using a sponge, microfiber cloth, soft-bristled brush, or another gentle tool.
You may need to let areas soak under wet cloths or use approved chemical detergents to soften hard-to-remove dirt. Never use harsh scrubbers like sandpaper, metal brushes, or steel wool, even on stuck-on dirt. These can permanently damage your roof. Then give the roof one final rinse with clean water to completely remove any soap or remaining dirt.
Safely Get Back Down
Once you and your spotter agree that the roof is clean, it’s time to get your feet safely back on land. Hand down any equipment and remove hoses, sponges, and other materials from the roof and gutters. Then, ask your friend or spotter to steady the ladder while you carefully climb back down.
DIY vs. Hiring a Pro
Cleaning a metal roof may sound like an easy DIY project. It just takes a hose and a little time, right? As you’ve read, though, it’s not so simple. It’s a multi-step process that takes careful planning and precautions to do correctly and safely.
Some homeowners feel comfortable cleaning their metal roofs, but if that’s not you, hiring a metal roof cleaning professional is the right way to go. They have the materials, expertise, and know-how to do the job right, and you can remain safely on the ground. Hiring a pro to clean a metal roof can also be relatively affordable. In most locations and for most jobs, the average metal roof cleaning cost is less than a dollar per square foot. Of course, the size, pitch, condition, and material of your roof will impact that cost.
Frequently Asked Questions
For the best chemicals to clean a metal roof, stick to gentle detergents such as dish soap, laundry detergent, or car-wash soap mixed in a diluted solution of ¼ cup of soap to 1 gallon of water. These mild cleansers are safe for most roof finishes but are still strong enough to remove remaining dirt particles. Chemicals like bleach or acids can damage your roof, poison landscaping and grass, and pose a hazard to you and your family. If your roof is very dirty or you think it requires chemical cleaning, call a roof cleaning professional.
It may require stronger cleansers or chemicals, higher-pressure spray, or scrubbing to completely remove algae from a metal roof. Start with a mild cleanser; if that doesn’t work and you're comfortable doing so, use a stronger mix of ⅓ cup of laundry detergent, 1 quart of bleach, and 3 quarts of water to gently scrub the algae with a soft-bristled brush. If algae is present across large portions of your roof, doesn’t come off with gentle scrubbing and cleansers, or is in hard-to-reach areas, this may be a job better left to a pro.
Moss grows in dark areas of roofs, including in corners and gutters. If left alone, it can grow under roofing and cause permanent damage. Here’s how to remove moss from metal roofs:
Soak the moss to soften it
Scrub it away with a soft-bristled brush, or pick it off with your hands (be sure to wear gloves)
Use a moss remover that’s compatible with metal roofing, following the manufacturer’s directions
Remove dead moss and rinse the roof thoroughly
Prevent future moss growth by trimming branches, cleaning gutters, and attaching zinc strips to moss-prone areas
Lauren is a full-time writer and editor, focusing on home improvement and construction. She enjoys combining her interest in renovating homes with real-life tips that can make the job easier. Her personal style emphasizes sustainability, retaining original character, revealing hidden beauty, and a love for all things old.
Lauren is a full-time writer and editor, focusing on home improvement and construction. She enjoys combining her interest in renovating homes with real-life tips that can make the job easier. Her personal style emphasizes sustainability, retaining original character, revealing hidden beauty, and a love for all things old.
The homeowners guide to Roof Cleaning
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