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Roof blisters and open seams on a Tampa flat roof mean heat and trapped moisture are working on the membrane, and a free inspection tells you which spots can wait and which need fixing now.
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Roofs run very hot
The EPA says regular roofs can reach 150 to 185 degrees in peak summer sun. Heat like that expands air trapped under a membrane and stresses every seam.
Long, hot summers
Normal highs at Tampa reach about 91 degrees in July and August, according to the National Weather Service, so a roof bakes for months, not weeks.
Typical published ranges for Tampa. The contractor's written estimate is the price, and the inspection is free.
| Work | Typical range |
|---|---|
| Blister and seam inspection and written estimate in TampaScheduled the day you call | Free |
| Blister repair | $250 to $1,500per repair |
| Seam repair | $200 to $1,000per repair |
| Membrane repair (cracks, punctures) | $250 to $1,750per repair |
| Infrared moisture scan$0.05 to $0.12 per sq ft | $5 to $12per square (100 sq ft) |
Blisters and open seams look different, but they come from the same place. A flat roof in Tampa sits in strong sun for most of the year. It heats up every day and cools off every night. That daily swing works on any weak spot in the membrane.
A blister is a bubble in the roof surface. Air and water vapor are trapped under it. An open seam is a spot where two sheets of roof membrane have come apart. Both can stay dry for a while. Both can turn into a leak.
Bubbles in the roof surface,
From the size of a coin to a few feet across.
Bubbles that feel soft or squish
When pressed. There may be water inside.
Blisters that are split or cracked
On top. These are open to water now.
Seam edges lifting
Or curling up where two sheets overlap.
A gap you can slide a finger into
Along a seam.
Dark lines or dirt trapped
Along a seam, a sign it has been open for a while.
Wrinkles or ridges
In the membrane near seams.
Leaks or stains inside
Below a seam or a cluster of blisters.
Research cited by the roofing industry found that the gas inside roof blisters is mostly air and water vapor. They start in small gaps between the roof layers, or between the membrane and what is under it. Those gaps can come from:
Moisture caught during the install,
Like dew or a passing shower on the materials.
Spots where the membrane did not fully stick
To the layer below.
Gaps between insulation boards
That were not filled.
Water that got in later
Through a leak and is now trapped.
Once a blister forms, the sun heats the trapped air and it expands. At night it cools and can pull more moist air in. The EPA says regular roofs can reach 150 to 185 degrees in peak summer sun. In Tampa, with normal highs near 91 degrees in July and August, that cycle runs for months. Blisters tend to grow.
Blisters show up most on built-up and modified bitumen roofs. Industry research points to them being more common on some types of modified bitumen than others.
Single-ply roofs like TPO, PVC and EPDM come in large sheets joined at seams. TPO and PVC seams are welded with hot air. EPDM seams are glued or taped.
Heat and movement
The roof grows and shrinks a little every day. Seams take that strain.
A weak weld or bond at install
A seam that was not fully welded or taped can let go early.
Adhesive breaking down
Glued and taped seams can soften and weaken with years of heat.
Ponding water
Sitting on a seam for days.
Wind
Storms that flex the membrane can stress seams, especially near edges.
Usually can wait for the next visit: small closed blisters that are not near seams, not in a walkway and not growing. Industry guidance says closed blisters are often best left alone, because a blister that keeps air in also keeps water out.
Fix soon: blisters that are split or cracked, blisters that have lost their gravel or coating, blisters in walk paths or near rooftop units, and any open seam.
Bigger talk needed: blisters across a wide part of the roof, or seams failing in many places. That often means trapped moisture under the roof, or a roof near the end of its life. An infrared scan shows how much of the roof is wet.
For blisters, the crew cuts out the damaged area, lets it dry, and patches it with new membrane. Wet insulation under it is replaced.
For seams, a TPO or PVC seam can often be cleaned and welded again. An EPDM seam is cleaned, primed and re-taped, or covered with a new strip.
Typical ranges from published cost guides are in the table on this page. Blister repairs run about $250 to $1,500 and seam repairs about $200 to $1,000. Your written estimate gives the real number.
Do not cut, pop or step on blisters
Take photos
Of blisters and seams with something for scale, like a shoe or tape measure.
Note the roof type
If you know it, plus the install date and any warranty.
Mark leaks inside
And match them to the area of the roof above.
Keep foot traffic down
In the area until it is checked.
Call (656) 233-6113 to schedule a free roof inspection and a written estimate with Tampa Commercial Roofing Co.
No. A closed blister keeps air in and water out. Cutting it open lets water in. Leave it alone, mark it, and have it checked. Blisters that are already split or cracked do need a repair.
Sometimes. Blisters often come from small gaps or moisture trapped during the install. They can also come from water that got in later. The inspector looks at where they are and how big they are to tell the difference.
The sun heats the air and water vapor trapped under the membrane, and it expands. When the roof cools, more moist air can get pulled back in. Each hot day can push the blister a little bigger.
Most open seams can be fixed. A TPO or PVC seam can often be cleaned and welded again, and an EPDM seam can be cleaned and re-taped. If seams are failing all over the roof, it may be time to talk about a coating or a new roof.
Not long in Tampa. An open seam lets water under the membrane in the next storm, and summer storms come almost every afternoon. Get it repaired before the wet insulation spreads.
