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Learn how to seal a metal roof in our handy guide. We cover inspecting areas prone to leaks and how to choose the best sealant.
Learn how to seal a metal roof and prevent leaks, drafts, or insects from getting into your home. It’s easy with the instructions below.
Metal roofs are extremely popular – not least because of their durability. A well-maintained metal roof can easily last 50 years or more, outpacing shingled roofs by decades. However, to keep the weather out, a metal roof must be sealed properly and periodically checked to ensure any aging sealant is replaced.
Key areas to inspect:
- Seams and joints: Check all overlaps between metal panels where water channels down the roof. Even small gaps can cause leaks over time.
- Fasteners: Screws, nails, and other fasteners may loosen or allow water ingress. Look for rust or gaps around each fastener.
- Roof valleys: These areas, where two roof angles meet, are prone to water pooling and leaks.
- Dormers and protrusions: Inspect around skylights, vents, antennas, and chimneys for cracks or failing sealant.
Check the bottom of the roofing plywood from your attic a few times a year. Look for damp spots, discolouration, or water stains – this will alert you to a possible leak. Also, inspect the roof if you can. Look for gaps in the sealant or obvious signs of aging. Repair these areas according to the directions below.
Water will get into any exposed seam or crack, so it is vital to seal every joint between metal pieces and around each fastener. Take proper precautions when working on a roof, such as using a stable ladder and wearing non-slip shoes. Here is how to handle a leak:
- Inspect the damage. Check the metal panels, seams, and fasteners for any signs of wear, corrosion, or damage. Replace or repair as needed.
- Thoroughly clean the area before applying new sealant. If old sealant is present, remove it with a putty knife. Use a wire brush to remove any rust, debris, or residue, and follow with a household cleaner to ensure the surface is completely clean and ready for sealing.
- Apply fresh sealant to replace what was removed and smooth it with a caulk tool or a gloved finger.
- Apply sealant around the edge of the patch and over each fastener.
Watch a few YouTube tutorials on metal roof patching to see techniques in action — this can help you feel more confident when applying sealant and installing patches.
When sealing a metal roof, choosing the right type of sealant is crucial for a durable, watertight result. Key options include:
- Silicone sealants: Highly flexible and weather-resistant, silicone works well on metal surfaces exposed to rain, sun, and temperature fluctuations. Ideal for sealing seams and fasteners, it remains flexible in cold and hot conditions and resists UV degradation.
- Polyurethane sealants: Strong and durable, polyurethane bonds well to metal and can handle expansion and contraction of roof panels. It is also resistant to moisture and can bridge slightly wider gaps than silicone.
- Hybrid or specialty sealants: Some products combine the flexibility of silicone with the strength of polyurethane, offering extra adhesion and durability for challenging roof areas.
Temperature and weather considerations:
- Check that the sealant can handle the high and low temperatures typical for your region. Some silicones and polyurethanes remain flexible from -40 °C to over 120 °C (-40 °F to 250 °F).
- Ensure the product is UV-resistant and suitable for prolonged outdoor exposure.
Focusing on sealant type and performance ensures a durable, watertight seal on any metal roof.