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Kansas City Commercial Roofers

Serving Kansas City and nearby areas

Bubbles and Blisters on a Flat Roof in Kansas City, KS

Bubbles in a flat roof mean air or moisture is trapped under the surface, and most can be watched while some need repair now, so get a free roof inspection and written price set up the same day you call.

Call now: (913) 347-6527 or book your free inspection online

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A few quick answers. A local roofing specialist calls you back the same business day.

Local to Kansas City

We connect property owners in Kansas City and nearby areas, including Fairfax District, Armourdale, Village West, Edgerton, Lenexa and Olathe, with one independent local commercial roofing specialist.

  • Hot roofs, bigger blisters

    Normal July highs in Kansas City reach about 89 degrees, and roofs get much hotter than the air. Heat makes the air and vapor in a blister expand.

  • Freeze and thaw

    Normal January lows in Kansas City sit near 19 to 21 degrees. Water that gets into a cracked blister freezes and pushes it further open.

What it costs

Typical published ranges for Kansas City. The contractor's written estimate is the price, and the inspection is free.

WorkTypical range
Roof inspection and written priceSet up through Kansas City Commercial Roofers Free
Most flat roof repairs $300 to $1,100
Repair area $2 to $10per square foot
Membrane repair $250 to $1,750

See typical commercial roofing prices in Kansas City

A bubble in the roof

A blister is a raised bubble in the roof surface. It can be the size of a coin or the size of a table. It may feel soft or spongy underfoot. It may swell on a hot afternoon and flatten out by morning.

Blisters are most common on older tar and gravel roofs and on modified bitumen, the rolled roofing with a gritty top. They also show up on rubber and white single-ply roofs where the sheet has come loose from what is under it.

The good news is that many blisters are harmless for years. The trick is knowing which ones are not.

What you will notice

Round or long raised bumps

In the roof surface.

Soft spots

That give when someone steps on them.

Bubbles that grow

In summer and shrink in winter.

Cracks across the top

Of a blister.

Bare spots

Where gravel or grit has worn off the top of a bump.

Loose, puffy areas

Of a single-ply sheet near the edges.

Blisters near a stain

On the ceiling below.

Why blisters form

Every blister starts as a small void, a spot where the layers of the roof did not stick together. That can happen when the roof was put down:

Moisture was trapped

In the felts or on the deck during install.

The hot asphalt was too thin

Or too cool to bond fully.

Gaps between insulation boards

Were not filled.

Dirt or debris

Got caught under the sheet.

Once the void is there, heat and moisture make it grow. Air and water vapor inside the void expand when the roof heats up. Then they shrink when it cools. Over many seasons, that pumping stretches the roof and makes the blister bigger.

Why it matters here

Hot summers. The National Weather Service puts normal July highs in Kansas City near 89 degrees. A dark roof gets much hotter than the air. That heat drives the swelling in a blister day after day.

Cold winters. Normal January lows sit near 19 to 21 degrees. When the top of a blister cracks, water gets in. It freezes at night and pushes the crack open wider. A dry blister in fall can be a leak by spring.

Foot traffic. Many roofs here carry HVAC units that get serviced often. Blisters along the path to those units get stepped on and break.

Which blisters can wait

Industry guides agree on this point. Deciding to repair a blister is a judgment call, and small closed blisters are often best left alone. A blister that keeps water out is not a leak.

Usually fine to watch:

  • Small blisters with no cracks or breaks.
  • Blisters away from walkways and units.
  • A few scattered blisters on a roof that is otherwise sound.

Repair soon:

  • Any blister that has cracked or split open.
  • Blisters in walkways or near rooftop units, where they will get stepped on.
  • Blisters near seams or laps, where they can pull a seam apart.
  • Loose areas of single-ply sheet at the edges and corners, where wind can lift them.
  • Large blisters, or many of them.

Call the same day: a broken blister with a fresh ceiling stain below it.

How blisters are usually fixed

The inspector checks whether the blister is dry or wet inside. On larger roofs, a moisture scan can show wet areas around the blisters.

Watch and record

Small, sound blisters get marked and photographed. They get checked at each routine visit.

Cut and patch

The crew cuts out the blistered area down to what is under it. If water got in, they remove the wet insulation, put in dry insulation of the same thickness, and patch the roof over it.

Re-secure loose sheet

On single-ply roofs, loose areas at edges get re-adhered or fastened, using the maker's repair method.

Bigger fix

If blisters cover much of the roof and the insulation is wet, the inspector may tell you a new roof makes more sense.

A few blisters are usually priced as a small patch job, not one by one. Typical ranges from national cost guides are in the table. Your price comes in writing after the inspection.

Before the inspection

Do not cut or pop blisters

It lets water in.

Keep foot traffic off them

Tell HVAC crews to step around.

Take photos

With something for scale, like a shoe or a tape measure.

Check the ceiling

Below for stains.

Find the roof's age

And any warranty or repair records.

Call (913) 347-6527 or send the form. Kansas City Commercial Roofers sets up the inspection with one independent local roofing contractor, and you get a written price.

Frequently asked questions

Should I pop a blister on my flat roof?

No. Cutting a blister open lets water in if it is not repaired right away. A blister that is closed and not cracked often keeps water out. Leave it for the inspector to judge.

Are blisters on a flat roof a sign it needs to be replaced?

Not by themselves. A few small blisters are common and can often be left alone. Many blisters spread across the roof, or blisters with wet insulation under them, may point to a bigger problem.

Why do roof blisters get bigger in summer?

Air and water vapor in the blister expand when the roof heats up. Blisters often swell on hot afternoons and shrink at night. Over many seasons, that pumping can stretch and crack the roof surface.

Can you coat over blisters?

A coating does not fix a blister. Open or cracked blisters need to be repaired first, and wet insulation should be found and removed before any coating goes on.

How much does it cost to fix roof blisters?

A few blisters are usually priced as a small patch job. National cost guides put most flat roof repairs at $300 to $1,100. If wet insulation is found under the blisters, the price goes up.

Other services

Common commercial roofing problems in Kansas City

Areas we serve around Kansas City

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