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Single-ply commercial roofing features a single layer of membrane installed over a substrate. Depending on the chosen installation method, the membrane can be installed using a combination of fasteners, adhesives and heat welding. There are certain problems unique to single-ply roofs, and in this blog, Sully Jones Roofing shares an overview of the most common of these problems.

Seam Failure

Single-ply roofing is installed as a monolithic layer over the substrate, much like a quilt laid over a bed, with the seams welded using heat and/or adhesive. Improper installation techniques include incorrect welding temperatures or using the wrong type of adhesive. Roof shrinkage caused by temperature changes should be accounted for during installation by allowing enough slack. Trained roofing professionals will know better than to install single-ply roofing tightly.


If the single-ply roofing is adhered to the substrate, it may develop blisters from moisture trapped under the membrane. The moisture could come from wet substrate, installation during unfavorable conditions or indoor humidity leaking through the roof. If you notice such blisters on your roof, do not puncture them under any circumstances. Take a picture of the blister with a tape measure for scale, check back every week and do the same thing for two or three weeks. If the blisters are increasing in size, make a roof repair appointment with your contractor.


Single-ply roofing isn’t intended to handle foot traffic or impact from hard objects. While its outer surface is durable, it’s not puncture-resistant. Fortunately, punctured single-ply roofing can be locally repaired using patches. Roofs with regular foot traffic should have built-up roofing (BUR) or other multi-ply roofing systems.

Ponding Water

It may not sound like much, but inch-deep ponding water can exert pressure up to 5.2 pounds per square foot. This is why the roof slope has to be carefully planned before roof installation begins. A so-called “flat” roof actually has a slight slope for proper drainage. If the ponding water on your commercial roof does not dry up after 48 hours, call a roofing professional. Ponding water can weaken the roofing seams, as well as encourage algae growth.

Sully Jones Roofing is your leading provider of commercial and residential roof replacement services. Give us a call at (619) 312-4018 or fill out our contact form. We serve customers in El Cajon, CA, and the surrounding areas.