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Metal Roof Leaks

If the metal roof on your home or building develops a leak, it must be fixed right away to prevent costlier damage to the structure underneath. Even the smallest metal roof leak can cause wet insulation, which is a major cause of roof failure.

Finding metal roof leaks can be the most difficult part of the repair. Leaks can originate from the opposite side of the building. A thorough understanding of the metal roof construction will help you pinpoint the cause of the roof leak.

Premature Roof Replacement due to Leaks

A majority of roof replacements are done because of leaks. Most of these roof replacements are not only premature but do not solve the leak problem on a long term basis.

Leaks on a metal roof will either come from the seams and penetrations. Most roofing professionals will try to solve the leak problem by caulking the screw heads and seams. What they do not realize is this approach only aggravates the leak problem.

metal roof leaks
Contrary to Popular Belief
Caulking the fastener heads may sound like a good idea but it really does not help stop the roof leak. As you can see in these photos, the water is already between the sheets and entering the building through the hole in the bottom sheet, well beyond the reach of caulks.
Mud Seals - One of the Major Causes of Metal Roof Leaks
The first rainfall of the year is usually a drizzle. Not enough to cause a leak but enough to moisten and wash down dirt that has accumulated on a roof.

Mud Seals are formed when dirt builds up along the seams by capilliary action (left middle). The mud dries up and forms a caulk like seal along the seams. With heavier rainfall, rain water can penetrate through gaps in the mud seal and remain inside the overlaps as it flows towards the gutter (left bottom).

The mud seals are usually wider towards the gutter where you have a larger volume of water flowing over the seam or near the purlins where the fastener constricts the flow of water (left bottom). Because of this, water that is already inside the roof overlap backs up and tries to go over the corrugation. As this happens, water finds its way to the fastener on the bottom sheet (left top).

It is not isolated. It is the entire Roof System.
As the water travels down the path on the fastener, it collects and runs the length of the purlins. The leak you see on the floor is not limited to the portion of the roof directly above it. It is the entire roof system. Each fastener slowly feeding rainwater to the purlins and the insulation underneath.
metal roof leaks
Don't Paint Your Roof
Have you ever wondered why a roof starts leaking a few months after it is repainted? Paint is not elastic. After exposure to UV rays, paints start to peel, crack, chalk or peel off. Failed paints inadvertently become mud seals as they crack along the seams and allow rainwater to penetrate.

Elastomeric Paints that claim to have the same elasticity as true elastomeric coatings also become brittle and chalky over time.
The Solution
Seam Detailing is the best solution to this problem. This is done by applying Acu-Tac along the seams and then rolling out 6" wide Acu-Fabric into the wet coating and then applying another layer of Acu-Tac over the Acu-Fabric.

Seam Detailing should be done on both vertical and horizontal seams, flashings and penetrations. Never do a horizontal seam without sealing the vertical seam first. It will aggravate the leak.

When the Acu-Tac is completely dry, apply Acu-Shield over the entire roof surface to create a "rubber-like" waterproof coating.

Use this link for Metal Roofing Application Specifications.
metal roofing leaks


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