How to Apply Metal Roof Sealer How to Apply Metal Roof Sealer

What You'll Need
Pressure washer
Mild detergent
Warm water
Wire brush
Trisodium phosphate (TSP)
Oxygen bleach
Mild detergent
Soft bristle broom
Rubber gloves

A roof sealer can help to extend the life of your metal roof considerably. It acts as a protective layer against rust and corrosion, which are two common problems with metal roofs. Application of sealant is one of the vital steps in metal roofing maintenance. This can be done every 2 to 4 years. The guide below shows you how to apply.

Step 1 – Sweep

Mount your ladder to the roof. Take a long handled broom with you. Sweep off the dust and debris so that you have a relatively clean surface.

Step 2 – Inspection

Inspect the roof carefully for signs of damage or worn out places. Tighten any loose fasteners. Replace stripped fasteners with similar ones. You want to be sure that you apply the sealer on a surface that is in good condition.

Step 3 – Rust and Loose Paint

If you spot areas with loose rust or paint, you’ll have to clear these first. This can be done with a wire brush or piece of sandpaper.

Step 4 – Stains, Algae and Heavy Grease

Mix 4 parts water, 1 part TSP and 1 part oxygen bleach in a small bucket. Place the solution in a spray bottle to enable easy application. Spray the affected areas and allow the solution 10 to 30 minutes to work. You may wish to scrub the areas with a soft bristle broom to facilitate the process.

Step 5 – Wash with Mild Detergent

Mix some mild detergent and warm water in a bucket. Use a scrubbing brush to wash away the cleaning detergents from the roof.

Step 6 – Pressure Wash

Use a pressure washer to thoroughly clean your roof. Set the pressure at 3,000 PSI for a thorough wash. Allow the roof to dry well.

Step 7 – Apply Primer

Primer helps improve the adhesiveness between the sealer and roof. Spray a primer evenly over the roof surface. Begin at the topmost part of your roof and work sideways. Proceed in this manner as you steadily move towards the lower roof section. If your roof has several sides that join in a peak at the top, spray primer in the same manner. However, work on one section first before you apply on another until you’ve covered all sections of the roof. Allow adequate time for the primer to dry completely.

Step 8 – Apply Sealer

It is best to apply in the same order as you did with the primer. Strive to apply the sealer uniformly. Be sure to cover up the repaired areas of the roof adequately. This will help to forestall further damages. For the sealer to work most effectively, two or three coats are necessary. However, you must allow each coat to dry completely before you apply another.


  • Wear shoes that have a good grip. This helps to prevent accidental slips and falls.
  • Avoid use of fasteners that are a different material on your roof. A chemical reaction may take place that compromises the integrity of your roof.
  • Wear rubber gloves to protect your hands from the effects of chemicals in the cleaning agents.
  • Select a day when rains are not in the weather forecast. It will allow you to complete your work effectively.

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