How to Seal a Metal Roof

By Amanda Lutz Updated May 10, 2024

Well-designed metal roofs are durable, safe, and energy efficient, lasting up to 70 years. Despite requiring relatively little maintenance, they need sealing to shield against moisture, prevent leaks, and extend their life span. In this guide, we’ll explain the benefits of sealing a metal roof, how to seal a metal roof, and how to maintain it.

What Are the Benefits of Sealing a Metal Roof?

Sealing your metal roof protects both the roof’s material and the structures below it, such as your rafters, attic, insulation, and home ceilings, which could be damaged by water or pests. By sealing and resealing your metal roof, you can keep your home safer and extend its life span.

Here are a few benefits of sealing a metal roof:

Additionally, sealing a metal roof can save you money in the long run by helping you avoid costly repairs and premature replacement.

Safety Considerations

If you decide to seal or reseal your metal roof on your own, there are several safety considerations to keep in mind. Consider the height and slope of the roof, how to handle sharp or heavy materials, and how to deal with wind or bad weather conditions.

Follow these safety tips if you perform your own roof work:

If your roof is very steep or you don’t feel comfortable sealing your roof as a do-it-yourself (DIY) project, hire a commercial roofing professional to complete the task for you.

Tools and Materials Needed

Before you can seal your metal roof, gather the following tools and materials:

You’ll also need the sealing materials themselves:

Preparing the Metal Roof for Sealing

Preparing the roof surface before you start the actual roof sealing process ensures that the roof is in good condition for an optimal seal.

1. Clean the Roof

Remove dirt, dust, organic matter, twigs, leaves, and other debris on your roof. Depending on the tools you have, you can pressure wash or scrub the roof with a mild metal roof detergent.

Thoroughly clean every exposed surface of the roof, including any raised lips or panel edges. You can also clean the surfaces of your gutters, gutter guards, and downspouts. Once you have cleaned and rinsed the surface, let it dry for at least 24 hours before continuing.

2. Repair Damage

As you clean the roof, inspect it for damage before sealing it. Here are a few signs that your roof needs repairs:

Repair any of these problems before continuing. If you notice severe roof damage, such as broken shingles, water damage, or clogged gutters, schedule a professional inspection or hire a certified contractor to make the repairs.

3. Ensure the Roof Is Dry

Your roof must be dry before you apply the sealant, or it won’t bond properly with the roof. Wait a day or two after cleaning your roof to seal it, and check the weather for misting or rain storms—even lingering dew can risk the effectiveness of your seal coat. Schedule the project for a warm, sunny day for the best results.

How to Seal a Metal Roof

This basic process includes applying a thin layer of sealant across the main surfaces, sealing the edges and fasteners for extra protection, and inspecting the roof after it dries. The steps are detailed below.

1. Apply the Sealant

Read the manufacturer’s guidelines and follow the listed instructions. Start applying the sealant with a roller brush or paintbrush from the top down. Work in vertical sections of shingles or panels so the sealant doesn’t become patchy or uneven, and apply a single thin layer at a time.

As you work, check for drips or missed patches. Reroll or brush over completed layers on windy days to smooth out any drips or unevenness.

If your roof is too big to seal at one time, plan a few stopping points. For example, you might complete one side of a gable roof and the other. This planning will help the finished product look more cohesive.

2. Seal Seams and Fasteners

Once you’ve sealed the main surfaces, use a paintbrush to apply a sealant to vertical or curled lips, exposed fasteners, and flashing. These exposed metal planes would have been difficult to reach with a roller brush.

You can also apply caulk sealant (rather than the liquid paint-like sealant) during this stage. Apply a thin bead of caulk to any joints or overlaps in the panels. Water can slip between these surfaces, so ensure there’s an unbroken caulk line over every potential gap.

3. Allow the Sealant to Cure

Depending on the chemicals used, you may need to let the metal roof seal cure for 48 hours or 96 hours (four days). Try to schedule your project for a week of dry weather. Generally, the warmer the weather, the faster your roof will cure. Once the sealant has cured, go back on the roof to check the surfaces and caulk.

How Do You Maintain a Sealed Roof?

You should replace roof sealants every few years, though some types can last up to 10 or 20 years. Here’s how you can protect your roof between sealing projects and extend the life of the seal coat:

Following these steps and conducting routine maintenance can help minimize costly repairs and roof damage.

Our Recommendation

Metal roofs should last for decades, and you can maximize your roof’s life span by sealing it with additional roof sealant and touching it up whenever you detect signs of wear. Along with sealing the roof system, we recommend cleaning it every year and monitoring it for potential damage along the seams. While you can complete this project on your own with the proper safety steps, consider hiring a professional roofing contractor if you don’t have the necessary tools and expertise to perform the task.

How to Seal a Metal Roof FAQ

Can I seal a metal roof in cold weather?

You can seal a metal roof in moderately cold weather. It’s more important that the weather is dry when sealing metal roofs, though applying the sealant in above-freezing temperatures is best. The sealant should also be around 70 degrees Fahrenheit, so homeowners should store roofing materials inside before starting.

How do I know if my metal roof needs to be sealed?

You’ll know if your metal roof needs to be sealed if you see gaps in the panels, worn sealant, corrosion, or damaged fasteners. If it’s been a few years since you last applied sealant, consider resealing your roof.

Can I paint my metal roof after sealing it?

You can paint your metal roof after sealing it, provided the sealant has cured and settled. It’s best to paint during spring or fall with periods of dry, temperate weather. Additionally, ensure your paint is compatible with a silicone-based sealant or polyurethane coating.