Metal roof repair and leak tracing

Finding the leak before fixing anything

Water rarely comes through a metal roof directly above the stain on the ceiling. It enters at a screw, a lap or a flashing, runs along the underside of the panel or the top of the underlayment, and drips off wherever gravity takes it, sometimes several metres away. A repair aimed at the stain is a guess.

We start with a drone survey of every plane, which shows backed-out fasteners, lifted trim, damaged panels and debris-filled valleys without anyone walking on a roof that may be steep or slippery. Then we go up where it is safe and look closely at the suspects, and into the attic to follow the water trail back up the slope. On a stubborn leak, a controlled water test on one section at a time tells us which detail is letting water in. It is also worth ruling out condensation. Frost or dripping under the roof in winter with no rain is often an attic ventilation problem, not a roof leak, and the fix is completely different.

Exposed-fastener roofs: screws, washers and holes

Most metal roof leaks we are called about are on screw-down roofs, and we repair them whoever installed them. Each screw seals with a rubber washer, and after years of sun and freeze-thaw those washers harden, shrink and crack. At the same time, the panel expanding and contracting against thousands of fixed screws slowly works some of them loose and wears the holes oval. The result is a roof that starts leaking in several places across the field at about the same age.

The repair is a re-screw. Every fastener on the affected planes is replaced with a new screw and washer, and holes that have worn oversize take a larger-diameter screw so they seal again. Screws that missed the strapping or purlin are pulled and the hole sealed properly rather than left in place. Where the roof is otherwise sound, a re-screw is a legitimate repair that buys many more years.

Standing seam repairs: seams, clips and single panels

Standing seam roofs leak far less often, and when they do it is usually at a detail rather than in the field: a pipe boot, a chimney flashing, a ridge closure, or the end of a valley. Those get re-flashed with trim bent on our brake to suit the existing profile and colour as closely as available coil allows.

When a panel itself is damaged, by a falling limb or a creased seam, it can usually be replaced on its own. The seams on either side are opened, the damaged panel comes out, and a new one is formed on site to the full length of the slope so no lap is introduced partway up. Seams that were never fully closed, or clips that were fixed too tightly to let the panel move, are corrected at the same time.

Sealant, penetrations and lap leaks

Sealant is a maintenance item on any roof. Around plumbing vents, exhaust fans, chimneys and skylights, the sealant on a metal roof eventually dries, cracks or lets go, and the boot or flashing it was supporting starts to leak. The repair is to remove the old sealant, clean back to bare metal, and renew it with a sealant made for metal roofing. Rubber pipe boots that have split are replaced, not patched.

Lap leaks are a different problem. On roofs where panels were overlapped end to end partway up a slope, or where side laps on screw-down panels sit on a shallow pitch, water can be drawn back through the lap by wind or held there by ice. Sometimes resealing and re-fastening the lap is enough. Sometimes the lap is simply in the wrong place for the pitch and will keep leaking, and the honest repair is to replace that run of panels in one length.

Oil-canning: cosmetic or a symptom

Oil-canning is the waviness you can see in the flat part of a metal panel, especially in low sun. On its own it is cosmetic and is not a leak or a structural problem. Some amount of it is normal on wide, flat panels, and it can come and go with temperature.

It is worth a closer look when it appears suddenly, when it gets worse each season, or when it comes with popping noises, distorted seams or fasteners pulling out. Those can point to a panel that was installed without room to expand, clips fixed too tightly, or a roof structure moving underneath. That is the version that needs a repair, and sometimes it means re-clipping or replacing panels.

Snow guard retrofits and storm damage

A metal roof that sheds snow onto a walkway, deck, car or gas meter needs snow retention whether or not it came with any. On standing seam, retrofit guards clamp to the seams without drilling through the panel, so they can be added years after the roof went on and placed exactly above where the slide causes trouble. On screw-down roofs the guards fasten through the panel into the structure, so they are placed deliberately and sealed properly.

After a wind or hail storm, we look for lifted ridge and edge trim, panels loosened or creased by wind, punctures from branches, and dents that have cracked the finish. A lot of storm damage on metal roofs is to the trim rather than the panels, and trim can be re-bent on our brake to match. If you are making an insurance claim, the photos and written notes from the inspection are the useful part.

When repair beats replacement, and when it does not

Repair is the right call when the panels themselves are sound, the leaks trace back to fasteners, sealant or a few details, and the roof has years of service left. That describes a lot of leaking metal roofs.

Replacement starts to make more sense when the panels are rusting through rather than just weathering on the surface, when the roof has already been re-screwed and the holes no longer hold, when laps are leaking because the panel layout is wrong for the pitch, or when leaks keep appearing faster than they can be fixed. Even then we will tell you which planes are worth keeping and which are not, and our metal roof replacement page explains what that process looks like.