How to seal a metal roof: Protect your home

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.

Joints that channel water down the roof must be resealed occasionally. Flashing around dormers and chimneys, valleys where divergent roof angles meet, seams in the roofing material, and fasteners tend to be areas where leaks can develop. 

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. Here is how to handle a leak:

1. Inspect the damage. Remove and replace any rotted wood or damaged roofing material. 
2. Remove the old sealant with a putty knife, then use a wire brush to thoroughly clean the area. Use a household cleaner to remove any dirt or residue.
3. Apply fresh sealant to replace what was removed and smooth it with a caulk tool or a gloved finger.
4. If a patch is needed, put a bead of sealant around the perimeter of the area to be patched. 
5. Install the patch of metal roof material (or reattach the existing piece) and secure it with appropriate fasteners.
6. Apply sealant around the edge of the patch and over each fastener.

Before the sheets of roof material are installed, all corners and valleys will need metal channels called flashing. Flashing consists of thin metal strips that are bent to fit a corner between two angles of a roof (valley) or between the roof and another structure, such as a dormer. 

During your repair, as each piece of flashing is installed (starting at the bottom and working upwards), set the next piece overlapping by several inches. Seal any exposed edges with an outdoor-rated waterproof sealant or roofing tar.

Finally, install the sheets of metal roof with an overlap to the flashing and carefully seal every seam and fastener as they are placed.

LePage 2 in 1 Seal & Bond Exterior functions as both an adhesive and sealant. It stands up to harsh weather conditions your roof will be exposed to, and uncured adhesive will not wash away even if exposed to unexpected early rain. Seal & Bond is resistant to mould and mildew and paintable after 24 hours.

Need a super strong adhesive to bond metal roof materials or flashing before sealing? Try LePage PL Premium Max Construction Adhesive. It creates a heavy-duty bond to wood, brick, masonry, metal, and more. This tough adhesive can be applied to wet or dry surfaces and withstands temperatures from -12° to 49°C (10° to 120°F). It has a fast grab but remains repositionable for 20 minutes.

Have a wide gap to span or need to seal a flat roof? Try LePage Epoxy Speed Set. The resilient two-part adhesive has incredible strength and sets in just 5 minutes. It bonds to metal, wood, tile, ceramic, and glass. Plus, it won’t shrink and can be tinted to match surrounding materials.