Commercial roof leak repair
Most leaks on a commercial roof start at a detail, not in the middle of the field: a flashing at a curb or wall, an opened seam, a blocked drain, a lifted edge or a puncture by a rooftop unit. A typical leak repair on a low-slope roof costs $300 to $1,100, averaging around $700, and larger repairs that involve wet insulation or a section of new membrane can run to $4,000 or more.
Water travels. On a membrane roof it can run under the sheet, along a deck flute or a joist and drip 20 or 30 feet from where it got in, which is why a good roofer starts on the roof, not under the stain.
Typical leak repair
$300 to $1,100
Average about $700. Big or wet-insulation repairs $150 to $4,000+.
Where commercial roofs usually leak
- Flashings at HVAC curbs, parapet walls, skylights and pipe penetrations, where the membrane turns up and is most stressed.
- Seams and laps that have opened from age, poor welding or thermal movement.
- Drains and scuppers blocked by leaves and debris, so water backs up over flashings it was never meant to reach.
- Perimeter edge metal lifted by wind, which lets the membrane peel back from the edge.
- Punctures from foot traffic, dropped tools, hail or service crews working on rooftop units.
- Pitch pans (filled boxes around odd-shaped penetrations) where the filler has shrunk and cracked.
What leak repairs typically cost
| Job | Typical price |
|---|---|
| Drain or scupper Clear, reseat or replace the clamping ring and strainer | $70 to $500 |
| Flashing Curbs, walls, pipe boots and pitch pans | $200 to $750 |
| Seam Re-weld, re-tape or strip-in an opened lap | $200 to $1,000 |
| Edge metal or drip edge Re-secure or replace a run of perimeter metal | $150 to $600 |
| Membrane section Cut out and replace a damaged area | $250 to $1,750 |
| Emergency call-out Added to the repair price, nights and weekends | +$200 to $350 |
Typical US prices from published national roofing cost guides, January 2026 editions, read November 2026. Installed, in US dollars, before any local tax. A guide, not a quote. Labor runs about $45 to $80 an hour and is most of the bill on a small repair. The repair cost estimator gives a range for your roof.
Before the roofer arrives
- Move stock, electronics and people away from the drip and put down a bucket or tarp. If water is near light fittings or electrical panels, switch off at the breaker and call an electrician.
- Photograph the ceiling, the date and time, and anything damaged. Your insurer and the roofer will both want them.
- Note when it leaks: only in heavy rain, after snow, when wind blows from one direction, or when the rooftop unit runs (condensate lines leak too).
- Find the roof plan, the roof's age, the installer and any manufacturer warranty. Many warranties are voided by repairs from an unapproved contractor.
- Do not send staff onto the roof to look. NRCA advises against people without the experience and equipment walking roofs, and an unprotected edge or skylight is a serious fall hazard.
What a lasting leak repair includes
A dry, clean, primed surface
Patches and seams only hold on clean, dry membrane. A roofer who patches over standing water or dirt is selling a callback.
The cause, not just the drip
Water travels under membrane and along deck flutes, so the wet ceiling tile is rarely under the hole. A good repair names where the water got in.
Materials that match the roof
TPO patched with TPO, EPDM with EPDM tape and primer, bitumen with bitumen. Mixing materials, or smearing roof cement on single ply, often fails within a season.
Wet insulation found and dealt with
Wet board loses most of its insulating value and holds water against the deck. Cores or a moisture survey show how far it has spread; badly wet areas are cut out and replaced.
Photos before and after
Dated photos of every repair, and its location on a roof plan, protect your warranty and any insurance claim, and help the next roofer.
Safe access and fall protection
Work near an unprotected edge on a low-slope roof calls for fall protection under OSHA 1926.501: guardrails, safety nets, personal fall arrest or the combinations the rule allows. Ask how the crew will get up and stay safe.
Water coming in now? Send us the building ZIP and we will find a roofer working in that area.
Ask for a free quoteHow a commercial roofer tracks down a leak
Find the entry point
The roofer walks the roof, checks the areas above the leak and upslope of it, and may use a moisture meter, infrared scan or cores.
Make it watertight
If water is coming in, a temporary repair first: a compatible patch, sealant or tarp held down so wind cannot lift it.
Permanent repair
The proper detail for the system: a heat-welded patch, taped seam, re-set flashing or a section of new membrane.
Report and photos
Before and after photos, what was found and what to budget for next, so you can decide between repair and replacement with facts.
Questions people ask
How much does it cost to fix a leak on a commercial roof?
Most leak repairs on low-slope roofs cost $300 to $1,100, with an average around $700. A simple drain or flashing fix can be under $500; a repair that means cutting out wet insulation and replacing a section of membrane can reach $4,000 or more.
Why does my flat roof leak only in heavy rain?
Usually because water is ponding high enough to reach a weak flashing or an open seam, often because a drain or scupper is partly blocked. Clearing drains is the cheapest fix and the first thing to check.
Can a roof leak be repaired in the rain?
A temporary patch, sealant or tarp can go on in wet weather to stop water coming in. A permanent repair needs a dry, clean surface, so the roofer will usually come back in dry weather to finish it.
Is a roof leak covered by commercial property insurance?
Sudden damage from a named event, such as wind or hail, is often covered; wear, poor maintenance and long-term leaks usually are not. Read your policy and report storm damage promptly with photos.
How long should a leak repair last?
A proper repair in matching material should last as long as the surrounding roof. If the same area keeps failing, or new leaks appear every season, the roof is likely near the end of its life.
Who is responsible for a roof leak in a leased building?
It depends on the lease. Under a triple net lease the tenant often pays for roof repairs; in many other leases the landlord keeps the roof and structure. Check the repair clause before you call anyone.
Where our information comes from
Get the leak looked at
The building ZIP, where to reach you, then a few taps about the roof. About a minute.
This is a free matching service, not a commercial roofer. We look for one who works in your area and tell you their name before anything is shared. Nobody contacts you until you say yes.
Thanks, your enquiry is in.
- We look for a commercial roofer who covers your building and does this kind of work, then email or call to tell you who it is.
- Your details reach that firm only if you say yes.
- They inspect the roof and give you a written price. No marketing from us, ever.