How do you find a leak in a commercial flat roof?

Start inside. Mark every wet spot and note when leaks happen. Then inspect the roof above and upslope: seams, flashings, penetrations, drains and walls. If the source is still unclear, an infrared survey can map wet insulation and electronic leak detection can locate breaches on compatible membranes. Cores confirm what is under the membrane.

Why does my commercial roof leak only when it rains hard or the wind blows?

Heavy rain can overwhelm partly blocked drains and push water over flashings. Wind-driven rain enters where a light rain cannot: open coping joints, edge metal, counterflashings, walls and windows above the roof line. These leaks often trace to wall and perimeter details rather than the open field of the membrane.

Is it the roof or the HVAC?

If the leak appears on dry days, or near rooftop units or above-ceiling air handlers, check condensate drains, pans and duct insulation first. In humid Houston weather, sweating ducts and clogged condensate lines are common. A roof leak usually lines up with rain, and timing is the fastest clue.

How fast should I report a roof leak to my insurer?

TDI tells policyholders to file a claim as soon as they can. Your policy may also set its own notice duties. TWIA says policyholders have one year from the date of damage to report. This is general information, not insurance advice, so confirm deadlines with your insurer or agent.

Can I make temporary repairs before the adjuster comes?

Generally, yes. TDI advises doing what you need to keep damage from getting worse, such as tarping, and keeping receipts. TWIA asks owners not to start permanent repairs before talking with a claims examiner. Photograph everything before and after temporary work, and check your own policy.

Does calling my roofer count as notifying the manufacturer?

Not for GAF. GAF's specimen Diamond Pledge NDL guarantee says notice to the roofing contractor is not notice to GAF, and that GAF must be notified in writing within 30 days. Other manufacturers have their own rules, so read the notice section of your warranty.

Commercial roof leak repair · Houston, Texas

Commercial roof leak repair in Houston: find the source, then fix it once.

A ceiling stain tells you water got in. It does not tell you where. Mammoth Services traces commercial building roof leaks across Houston and the Bay Area to the actual entry point, repairs it, and hands you a written record you can use with your insurer, your warranty holder and your tenants.

Book a Roof Assessment Call (832) 416-1566

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The short answer

Roof Leak Repair: what Houston owners should know.

Commercial roof leak repair in Houston starts with leak detection: mapping where water appears inside against the roof above, inspecting the likely paths, and, when needed, using infrared or electronic leak detection to narrow the search. Many leaks are not roof leaks at all. HVAC condensate, ductwork and plumbing can look the same from below.

Mammoth Services traces the source, makes temporary protection where water is still entering, repairs the failure, and documents findings with photos and dates. That record matters because insurers, TWIA and manufacturer warranties each have their own notice rules. For an active leak, call Mammoth Services at (832) 416-1566.

Why it is hard

Why commercial roof leaks show up far from the hole

Low-slope roofs hide the path water takes.

Water travels before it drips

Under a membrane, water can run along the top of the insulation, follow the flutes of a steel deck, or wick along a joint before it finds a fastener hole or a deck seam to drop through. The stain inside is where the water finally fell, which can be many feet from where it entered. That is why a patch over the stain so often fails.

Timing is evidence

When a leak appears says a lot. A leak during every rain points toward an open seam, puncture or drain problem. A leak only in wind-driven rain points toward walls, copings, edge metal and counterflashings. A leak on a dry day points away from the roof and toward HVAC or plumbing.

Wet insulation keeps leaking

Once insulation is saturated, it can keep releasing water for days after the rain stops. Finding the entry point is half the job. Finding how far the water spread decides whether the repair is a patch or a section replacement.

Leak detection

Commercial roof leak detection methods, and what each one can tell you

No single tool finds every leak. We add methods only when the roof needs them.

Interior mapping and roof inspection

We mark every interior wet spot, then match those spots to the roof plan: rooftop units, curbs, drains, penetrations, walls and seams above and upslope. A trained eye on the roof finds most leaks at this stage.

Interior locations tied to roof features
Seam probing and flashing checks
Controlled water testing of a suspect detail when appropriate

Infrared moisture survey

Wet insulation holds heat differently than dry insulation, so a thermal camera at night can show where water has spread. ASTM C1153 sets practice for locating wet insulation with infrared imaging, including weather conditions and verification with invasive tests. The standard itself says it does not determine the cause of moisture or its point of entry.

Maps the extent of wet insulation
Results confirmed by cores or probes
Shows spread, not the hole

Electronic leak detection

Electronic leak detection, covered by ASTM D7877, uses electrical conductance to find breaches in a membrane. IIBEC's technical advisory notes it needs a conductive layer directly under the membrane, that high-voltage testing cannot be used on black EPDM, and that it should not be the only quality check.

Low-voltage methods on a wetted membrane
High-voltage methods on a dry membrane
Depends on the roof assembly being compatible

Cores and test cuts

A small core cut through the roof shows exactly what is under the membrane: how many layers, what insulation, and whether it is wet. It gives hard evidence for repair versus replacement.

Confirms layer count and materials
Verifies infrared readings
Patched to match the roof system

Sources: ASTM C1153, ASTM D7877, IIBEC Technical Advisory 018, electronic leak detection.

False leaks

When the commercial building roof leak is not the roof

In Houston's humidity, a surprising number of service calls end at a mechanical or plumbing source.

Condensate lines and pans

Clogged condensate drains and overflowing drain pans on rooftop units or above-ceiling air handlers drip on hot, dry days.

Sweating ductwork

Poorly insulated supply ducts in humid ceiling spaces collect condensation that drips onto tiles in patterns that look like roof leaks.

Plumbing and roof drain piping

Leaking roof drain bodies, cracked drain leaders and supply lines above the ceiling put water exactly where a roof leak would.

Walls, copings and windows

Open coping joints, failed parapet caps, masonry and window perimeters let wind-driven rain in above the roof line, then it runs down inside the wall.

Skylights and hatches

Condensation on skylight frames and roof hatches, or failed curb flashing, can look like a membrane failure.

Exhaust fans and vents

Kitchen and bathroom exhaust fans, gravity vents and unhooded penetrations pull in rain in storms and drip grease or condensate in between.

First hour

Emergency roof leak steps for facility teams

What happens in the first hour limits the damage and protects your claim. These steps are general guidance, not a substitute for your own safety procedures.

Isolate electrical hazards
If water is near light fixtures, panels or equipment, shut down power to that area through your normal procedure and keep people clear. A sagging ceiling tile full of water can fall without warning.
Contain and divert
Use buckets, plastic sheeting and wet vacuums. Move inventory, records and electronics. Cover what cannot be moved.
Start a leak log
Write down when the leak started, the weather at the time, and each interior location. Take wide and close photos and video before cleanup. TDI's claim guidance tells policyholders to photograph all damage and keep receipts for expenses.
Keep staff off the roof
A wet, windy or dark roof is dangerous. Temporary protection should be done by trained roofers with fall protection.
Call for leak response
Call Mammoth Services at (832) 416-1566. Tell us the roof type if you know it, whether it is under warranty, and what your leak log shows.
Notify the right parties
Depending on your situation, that may include your insurer or agent, TWIA, the roof manufacturer, your landlord or your tenants. The next section explains why timing matters.

Source: TDI, getting your insurance claim paid. In the City of Houston, tarping does not require a permit, per Houston Public Works.

Notice clocks

Insurance and warranty notice deadlines after a roof leak

Several clocks can start the day you find a leak. This table summarizes what the published sources say. It is not legal or insurance advice. Confirm your own deadlines with your insurer, agent or attorney.

Who	What the source says	What owners often do
Your property insurer	TDI tells policyholders to file a claim as soon as they can and to make temporary repairs to keep damage from getting worse. Insurers generally have 15 business days to acknowledge a claim.	Report promptly, read the policy's notice and duties section, and keep receipts for temporary work.
TWIA (coastal windstorm policies)	TWIA says policyholders have one year from the date the property was damaged to report a claim, and asks owners not to start permanent repairs before talking with a claims examiner.	Make temporary repairs, document everything, and talk to TWIA before permanent work.
GAF Diamond Pledge NDL guarantee	GAF's specimen guarantee says the owner must make sure GAF is notified about the leak in writing within 30 days, and that notice to the roofing contractor is not notice to GAF. Emergency temporary repairs are allowed at the owner's expense.	Send written notice to GAF directly, then schedule a GAF-certified contractor.
Other manufacturer warranties	Terms vary by manufacturer and warranty type.	Find the warranty document and follow its notice section to the letter.
Your lease	Who reports, who repairs and who pays depends on the lease.	Check notice clauses in the lease and send notice in writing.

Sources: TDI, rights for commercial property insurance; TWIA claims; GAF EverGuard Diamond Pledge NDL Roof Guarantee (specimen). If a storm caused it, see our guide to commercial roof storm and hail damage.

The record

What our written leak findings include

Every Mammoth leak call ends with documentation.

Source and cause

Where the water entered, how it traveled, and what failed: a seam, a flashing, a penetration, drainage, wind damage or a non-roof source.

Marked roof plan or photo key
Interior locations matched to roof locations

Dated photos

Before, during and after photos of the failure and the repair, with dates, so the condition at the time of the leak is clear later.

Wide shots for location
Close shots for the failure itself

Work performed and what remains

Temporary protection, permanent repair, materials used, and any conditions that still need attention, such as wet insulation, worn seams or blocked drains.

Separates urgent items from planned items
Notes warranty-sensitive details

Service area

Roof leak repair across Houston and the Bay Area

Leaks follow the building and the weather. These are the patterns we watch for in each city.

Houston, TX

In older Houston warehouses and offices, leaks often trace back to years of rooftop equipment changes and abandoned penetrations that were never properly closed. Commercial roofing in Houston

Webster, TX

Medical and office buildings in Webster run HVAC hard all year, so condensate overflow is one of the first things we rule out before cutting into a roof. Roof repair in Webster

Clear Lake, Houston

Office and research buildings around Johnson Space Center often protect sensitive equipment, where an early electronic or infrared survey can be worth it. NWS recorded a 65 knot Beryl gust at Clear Lake Park. Flat roof repair in Clear Lake

Nassau Bay, TX

Wind off Clear Lake drives rain sideways into copings and edge metal on Nassau Bay's lakefront buildings, so wall-line leaks are common after storms. Storm repair in Nassau Bay

Seabrook, TX

For Seabrook properties east of State Highway 146, inside TDI's designated catastrophe area, TWIA's one-year reporting window makes dated leak records especially important. Roof repair in Seabrook

League City, TX

Retail tenants in League City notice leaks fast, so a clear source finding helps landlords and tenants settle who handles what under the lease. Roof repair and coatings in League City

La Marque, TX

Salt air in Galveston County speeds corrosion at metal flashings and fasteners, a frequent hidden entry point on La Marque industrial roofs. Roof repair in La Marque

Dickinson, TX

Dickinson sits in TDI's Inland I windstorm zone, and a leak after a named storm may involve a TWIA policy, so we document wind damage and age-related wear separately. Roof repair in Dickinson

Santa Fe, TX

On Santa Fe's metal shop and church roofs, leaks often come from worn fastener washers and open end laps rather than the panels themselves. Roof repair in Santa Fe

Pasadena, TX

On Pasadena plant and warehouse roofs along the Ship Channel, leak response works within site safety rules, and process exhaust can contaminate membranes around vents. Roof repair in Pasadena

Windstorm areas: TDI Harris County map, TDI Galveston County map. Beryl gust: NWS post-tropical cyclone report.

Questions

Roof Leak Repair: direct answers.

If your question is not here, call Mammoth Services at (832) 416-1566.

01
How do you find a leak in a commercial flat roof?
Start inside. Mark every wet spot and note when leaks happen. Then inspect the roof above and upslope: seams, flashings, penetrations, drains and walls. If the source is still unclear, an infrared survey can map wet insulation and electronic leak detection can locate breaches on compatible membranes. Cores confirm what is under the membrane.
02
Why does my commercial roof leak only when it rains hard or the wind blows?
Heavy rain can overwhelm partly blocked drains and push water over flashings. Wind-driven rain enters where a light rain cannot: open coping joints, edge metal, counterflashings, walls and windows above the roof line. These leaks often trace to wall and perimeter details rather than the open field of the membrane.
03
Is it the roof or the HVAC?
If the leak appears on dry days, or near rooftop units or above-ceiling air handlers, check condensate drains, pans and duct insulation first. In humid Houston weather, sweating ducts and clogged condensate lines are common. A roof leak usually lines up with rain, and timing is the fastest clue.
04
How fast should I report a roof leak to my insurer?
TDI tells policyholders to file a claim as soon as they can. Your policy may also set its own notice duties. TWIA says policyholders have one year from the date of damage to report. This is general information, not insurance advice, so confirm deadlines with your insurer or agent.
05
Can I make temporary repairs before the adjuster comes?
Generally, yes. TDI advises doing what you need to keep damage from getting worse, such as tarping, and keeping receipts. TWIA asks owners not to start permanent repairs before talking with a claims examiner. Photograph everything before and after temporary work, and check your own policy.
06
Does calling my roofer count as notifying the manufacturer?
Not for GAF. GAF's specimen Diamond Pledge NDL guarantee says notice to the roofing contractor is not notice to GAF, and that GAF must be notified in writing within 30 days. Other manufacturers have their own rules, so read the notice section of your warranty.

Sources

This page is general information for commercial property owners, not legal, insurance or engineering advice. Warranty eligibility and terms are set by the manufacturer.

Commercial Roof Repair Storm and Hail Damage Commercial roof repair storm response nassau bay, tx Roof management with Roof React Commercial roofing services

Next step

Talk to Mammoth about your roof.

Call Mammoth Services at (832) 416-1566, or book a roof assessment and tell us about your building. For planned work, book a roof assessment call.