Membrane-covered flat roofs have seams where two pieces of membrane meet. These seams are adhered down and then sealed over, but time can lead to leaks at these weaker points. Knowing when to repair and when to replace is important.

Causes of Seam Leaks

Seam leaks are often a result of age. As the roof ages and weathers, particularly from UV exposure, the membrane may shrink back at the seams. The result is a gap that can quickly become a leak. Weathering in general, such as uplift from wind, can also cause a seam to lift up as adhesion fails. Standing water on the roof can weaken the adhesive and speed the process.

Sometimes the issue stems from installation problems. A seam that was poorly adhered, for example, is more prone to leaks. Membranes stretched too tightly are more likely to shrink apart at the seams. Improper anchoring is another issue, as this can lead to roof uplift and seam failure.

Repair Options

Repair options do depend on the severity of the damage as well as the cause. Loss of adhesion and minor shrinkage are typically repairable, though, if the rest of the roof is in great condition. For adhesion loss, the roofer will apply a new adhesive and stick down the membrane. They will then seal over the seam with roofing tar so that it won't come loose again.

Shrinkage is a more involved repair. A new strip of membrane is cut. This strip is large enough to overlap the seam gap. It is then adhered in place. Finally, tar or similar sealant is applied over the patched area so that no moisture can get in. Fixing a gap is similar to repairing a puncture on a flat membrane roof.

Replacement Signs

Sometimes replacement is a better option than attempting to repair. If there are a lot of damages on the roof, such as multiple seams coming apart, then repairs aren't likely to last long enough to make them worthwhile. At this point, a new roof will be comparable in cost, and you won't have to worry about damages for a while.

Seam damages that have occurred to other issues with the roof may also necessitate replacement. For example, if uplift is an issue, then chances are it will happen again unless a new, properly anchored roof is installed.

Contact a commercial roof repair service if you have a seam leak problem on your roof and need commercial roof repair.

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