Gulf Coast guide · Wind, code, and insurance
Texas windstorm requirements for commercial roofs (2026)
On the upper Texas coast, one commercial roof answers to four different wind numbers: the code design wind speed, the TDI windstorm certificate, the insurer’s FM rating, and the warranty’s wind limit. They are not the same number. This guide from Mammoth Services, a commercial roofing contractor on East NASA Parkway in Houston’s Clear Lake area, explains each one with public data, so facility managers, owners, and public agencies can plan a roof replacement or repair that holds up and stays insurable.
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The short answer
What a Texas coastal roof has to meet.
If you read nothing else, read this. Each point is explained, with sources, further down the page.
- The code sets the design wind speed. Since April 1, 2026, TDI’s windstorm program uses the 2024 International Building Code, which references ASCE 7-22. Published local values run from 137 to 163 mph, depending on the city and the building’s risk category.
- TDI certification decides TWIA eligibility. In the designated catastrophe area (all of Galveston County, and parts of Harris County east of SH 146), re-roofs and roof repairs must be inspected during the work to earn a WPI-8.
- FM ratings are pressures, not speeds. A Class 1-90 roof resisted 90 pounds per square foot in testing. It has nothing to do with 90 mph.
- Warranty wind limits are far lower. GAF’s standard single-ply guarantee covers leaks from winds up to 55 mph. Pressure at a 146 mph design wind is about seven times greater.
- Roofs fail at the edges first. After Hurricane Ian, 71% of damaged low-slope membrane and built-up roofs IBHS studied also showed flashing or coping damage.
The numbers that frame it
Four facts worth sitting with.
The upper Texas coast is not short on storms. It is short on recent memory of a major one.
Hurricane impacts on the Texas coast north of Matagorda Bay, 1865 to 2024. About one every five years. (NOAA AOML)
Since the last Category 3 or stronger impact on this stretch: Alicia, August 1983. Most roofs here have never seen one. (NOAA AOML)
Texas buildings damaged by Beryl, a Category 1, with 239 more destroyed. (NHC, citing the Texas Division of Emergency Management)
Mph: GAF’s standard single-ply warranty wind limit, against Santa Fe’s Risk Category II design wind. (GAF; City of Santa Fe)
Sources: NOAA AOML hurricane impacts 1851-2025; NHC Tropical Cyclone Report, Beryl, May 1, 2025; GAF coverage matrix COMEG858 V5.1; City of Santa Fe FAQ, 2023.
One roof, four wind numbers
The numbers owners mix up, side by side.
Ask four people “what wind is this roof rated for?” and you can get four honest, different answers. Here is what each one means.
| Number | Who sets it | What it measures | Typical value here | Where you see it |
|---|---|---|---|---|
| 1. Code design wind speed | The building code: 2024 IBC, which references ASCE 7-22 | A 3-second gust at 33 feet in open terrain, mapped by risk category. Risk Category II is a 700-year event. | 137 to 163 mph in published local values (Santa Fe, League City, Seabrook) | Engineered drawings, wind uplift calculations, the city permit |
| 2. TDI windstorm certificate (WPI-8) | Texas Department of Insurance | Not a separate speed. It certifies the work was built and inspected to TDI’s adopted code at that address. | Required for TWIA coverage in the designated catastrophe area | WPI-1 before work, inspections during work, WPI-8 at the end |
| 3. FM rating | FM Approvals and FM Global Data Sheets 1-28 and 1-29 | Uplift pressure in psf that the tested assembly resisted, such as Class 1-90. Not mph. | Set by calculation for the building, field, perimeter and corners | FM Global insured sites, specs that call for FM Approved assemblies, RoofNav |
| 4. Warranty wind limit | The roofing manufacturer | The wind speed above which the guarantee stops covering leaks, as defined in the guarantee | GAF: 55 mph standard, up to 120 mph on select systems for purchase | The guarantee document and its coverage matrix |
The trap is reading these as one scale. A roof can carry a valid WPI-8, sit on a 150 mph design, and still have a warranty that stops covering wind-driven leaks at 55 mph. None of that is wrong. Each document answers a different question: will the building stand (code), will TWIA insure it (TDI), will the insurer’s engineers accept it (FM), and what will the manufacturer pay to fix (warranty).
Chart 1
Wind pressure grows with the square of speed.
Each number below comes from a different source and is measured a different way. What they share is physics: pressure on a roof rises with the square of wind speed.
View the data
| Wind speed | What it is | Pressure vs 55 mph |
|---|---|---|
| 55 mph | GAF NDL base wind coverage | 1.0x |
| 75 mph | Beryl 2024 peak gust, Clear Lake Park, Seabrook (NWS) | 1.9x |
| 97 mph | Beryl 2024 peak gust, Brazoria County (NWS) | 3.1x |
| 120 mph | Highest GAF wind upgrade listed (select systems) | 4.8x |
| 146 mph | Santa Fe design wind speed, Risk Category II | 7.0x |
| 163 mph | Santa Fe design wind speed, Risk Category IV | 8.8x |
Sources: 2024 IBC Section 1609.3; TDI Adopted Building Codes; Building Enclosure, on FM uplift ratings, Feb 2012; GAF COMEG858 V5.1; Santa Fe, League City and Seabrook published values.
Terms, defined
Plain definitions you can quote.
The vocabulary is where most of the confusion starts. These are the definitions this guide uses.
- Basic (design) wind speed
- The wind speed a building is designed for, mapped in the building code. In the 2024 IBC it is a 3-second gust at 33 feet in open terrain. For a Risk Category II building it corresponds to a 700-year event, about a 7% chance of being exceeded in 50 years.
- Risk category
- How important the building is after a storm. Category I covers low-hazard buildings such as utility structures, II most commercial buildings, III schools and assembly buildings, and IV hospitals and emergency facilities. Higher categories use rarer, stronger design winds: 1,700 years for III and 3,000 years for IV.
- Designated catastrophe area
- The coastal area where TDI’s windstorm inspection program applies: 14 first-tier counties, including Galveston, Brazoria and Chambers, plus parts of Harris County east of SH 146 inside La Porte, Morgan’s Point, Pasadena, Seabrook and Shoreacres.
- WPI-1 and WPI-8
- The WPI-1 is the application that tells TDI about a project before work starts. The WPI-8 is TDI’s Certificate of Compliance, issued when inspected work meets the adopted code. TWIA uses the WPI-8 for eligibility.
- Windborne debris region
- The part of the hurricane-prone region where flying debris is expected, so glazing must be impact-resistant or protected. TDI says most of the designated catastrophe area is now inside it.
- FM rating (for example, Class 1-90)
- An FM Approvals classification. The number is the uplift pressure, in pounds per square foot, that the tested assembly resisted. FM applies a safety factor of two to calculated pressures, so a 1-90 field rating covers calculated field uplift up to 45 psf.
- NDL warranty
- A “no dollar limit” manufacturer guarantee that pays to repair covered leaks without a cap on cost, within its terms. Wind coverage stops at the speed the guarantee states.
- Edge metal (ES-1)
- The metal at the roof perimeter that holds the membrane edge down. The 2024 IBC requires edge systems on low-slope membrane roofs to be designed for code wind loads and tested to ANSI/SPRI ES-1 methods RE-1, RE-2 and RE-3.
Sources: 2024 IBC Chapter 16, Figure 1609.3 notes; 2024 IBC Section 1504.6; TDI general questions; TDI Adopted Building Codes; Building Enclosure, Feb 2012. Risk category examples follow 2024 IBC Table 1604.5 in summary form; the engineer of record assigns the category.
TDI windstorm certification
How the WPI-8 works on a roof project.
TDI’s program is about insurability. If the building is in the designated catastrophe area and will be insured through TWIA, the roof work has to be built and inspected to TDI’s adopted code. That includes re-roofs and roof repairs.
- 01
Before work: file the WPI-1
TDI says you must apply, with Form WPI-1, before construction begins. Under Texas Insurance Code Sec. 2210.251(c), a late application may mean no WPI-8 is issued unless plans, calculations, testing information and other documentation are submitted.
- 02
During work: inspections in progress
A TDI inspector or an appointed Texas licensed professional engineer inspects while the work is under way. TDI inspectors try to inspect within 48 hours of the requested date, excluding weekends and holidays, and charge no fee. The La Marque field office serves Galveston and Harris counties.
- 03
After work: the WPI-8
When the work passes, TDI issues the WPI-8 Certificate of Compliance. Keep it with the building records; TWIA, lenders and buyers ask for it.
- 04
If an inspection was missed
TDI says a re-roof or repair completed without an inspection needs a post-construction inspection by an appointed Texas licensed professional engineer. That is slower and costlier than inspecting during the work.
“Construction must be certified to be eligible for windstorm insurance coverage through TWIA.”
One local wrinkle: League City’s commercial packet asks for a WPI-8 at final occupancy and says the building must meet the 145 mph wind speed. City rules can add to TDI’s, so check both.
Sources: TDI general questions; TDI inspection process, updated Jul 21, 2025; TWIA Insurability Requirements; TDI Adopted Building Codes; League City Commercial SOP. Insurance eligibility is decided by TWIA and your insurer.
City and county lookup
Where the rules apply around Clear Lake and Galveston Bay.
TDI’s map follows county lines in Galveston County and SH 146 in Harris County. Design wind speed follows the address. Where a city has not published a value, the engineer of record looks it up.
| City | County | TDI windstorm area | Published design wind speed | Mammoth guides |
|---|---|---|---|---|
| Webster | Harris | No | Look up by address | Roofing in WebsterRoof repair |
| Clear Lake (City of Houston) | Harris | No | Houston requires a site-specific lookup (Houston Permitting Center) | Roofing in Clear LakeFlat roof repair |
| Nassau Bay | Harris | No | Look up by address | Roofing in Nassau BayStorm response |
| Seabrook | Harris | East of SH 146 only | 150 mph citywide, both sides of SH 146 (City Code Secs. 18-121, 18-122) | Roofing in SeabrookRoof repair |
| Pasadena | Harris | East of SH 146 only | Look up by address | Industrial roofing in PasadenaRoof repair |
| League City | Galveston | Yes, entire county | 145 mph (City commercial SOP) | Roofing in League CityReplacement and coatings |
| Dickinson | Galveston | Yes, entire county | Look up by address | Roofing in DickinsonRoof repair |
| La Marque | Galveston | Yes, entire county | Look up by address | Roofing in La MarqueRoof repair |
| Santa Fe | Galveston | Yes, entire county | 137 / 146 / 156 / 163 mph for Risk Categories I to IV (City FAQ, 2023) | Roofing in Santa FeRoof repair |
Sources: TDI Harris County map; TDI Galveston County map; TDI general questions; city sources linked in the table. “Look up by address” means no city-published value was found; TDI points to tools such as the ASCE 7 Hazard Tool, and the engineer of record confirms the speed. Santa Fe’s and League City’s values were published before TDI moved to the 2024 code on April 1, 2026; confirm the current value with the city for each project.
What the 2024 code says
The roof sections that matter on a coastal re-roof.
The 2024 IBC, as adopted for TDI’s windstorm program, references ASCE 7-22. For low-slope roofs the method is familiar. The map, and the edges, deserve a second look.
Section 1504.4: membranes
Mechanically attached or adhered roof coverings must resist the code’s components and cladding wind pressures. Built-up, modified bitumen and single-ply systems are tested to FM 4474, UL 580 or UL 1897.
Section 1504.6: edge systems
Metal edge systems on low-slope membrane roofs are designed for code wind loads and tested to ANSI/SPRI ES-1 methods RE-1, RE-2 and RE-3, using the mapped basic wind speed.
Section 1512: reroofing
A roof replacement removes all existing layers down to the deck. A recover over an existing roof is allowed only under the conditions listed in Section 1512.3.
“Speeds increased in parts of Texas and the Florida Panhandle.”
Smith’s review also notes that, for roofs with slopes up to 1½ in 12, ASCE 7-22 made no changes to the zone layout or pressure coefficients. In other words, the low-slope math did not change. The input did: an updated hurricane model raised mapped speeds in parts of Texas.
He flags a point that matters on older coastal buildings. Where existing glazing that does not meet current debris rules stays in place and a new roof goes on, the ASCE 7-22 Commentary says to assume the glazing can be breached and to check the building’s enclosure classification. A breached window raises internal pressure. FM Global puts the increase in uplift pressure at 10 to 30 percent when windows or doors break.
Sources: 2024 IBC Chapter 15 via UpCodes, Sections 1504.4, 1504.6, 1512; Professional Roofing, May 2023; FM Global P0283. Section numbers checked against the UpCodes text of the code as adopted for the TDI windstorm program on Oct 7, 2026.
The storm record
Frequent hurricanes. A long quiet spell at the top of the scale.
Since Alicia in 1983, every hurricane counted on this stretch of coast has been a Category 1 or 2 here. Those storms still do billions in damage, and roofs are where wind losses usually begin.
Chart 2
160 years of hurricanes on the upper Texas coast.
NOAA counts 33 hurricane impacts on the Texas coast north of Matagorda Bay from 1865 through 2024. That is roughly one every five years, and seven were Category 3 or stronger.
View the data
| Decade | Cat 1 | Cat 2 | Cat 3 | Cat 4 |
|---|---|---|---|---|
| 1860s | 2 | 0 | 0 | 0 |
| 1870s | 0 | 1 | 0 | 0 |
| 1880s | 0 | 2 | 0 | 0 |
| 1890s | 2 | 0 | 0 | 0 |
| 1900s | 0 | 0 | 1 | 1 |
| 1910s | 1 | 0 | 0 | 1 |
| 1920s | 1 | 0 | 0 | 0 |
| 1930s | 0 | 0 | 0 | 1 |
| 1940s | 2 | 4 | 1 | 0 |
| 1950s | 1 | 1 | 0 | 0 |
| 1960s | 0 | 0 | 1 | 0 |
| 1970s | 0 | 0 | 0 | 0 |
| 1980s | 3 | 0 | 1 | 0 |
| 1990s | 0 | 0 | 0 | 0 |
| 2000s | 1 | 2 | 0 | 0 |
| 2010s | 0 | 0 | 0 | 0 |
| 2020s | 3 | 0 | 0 | 0 |
Chart 3
Category is not the bill.
Ike came ashore as a Category 2 on this coast. Adjusted for inflation, it cost more than four Alicias. Beryl, a Category 1, still ran past $7 billion.
View the data
| Storm | Note | Cost (CPI-adjusted) |
|---|---|---|
| Alicia, 1983 | Cat 3 on this coast | $9.5B |
| Rita, 2005 | Cat 2 on this coast | $29.4B |
| Ike, 2008 | Cat 2 on this coast | $43.2B |
| Harvey, 2017 | Cat 4 landfall near Rockport; losses mostly flood | $160.0B |
| Beryl, 2024 | Cat 1 on this coast | $7.2B |
What Category 1 and 2 storms did here
Beryl, July 8, 2024. Landfall near Matagorda at 80 knots, a Category 1. The National Weather Service recorded peak gusts of 97 mph in Brazoria County, 84 mph at Houston Hobby, 82 mph on the Galveston Causeway, and 75 mph at Clear Lake Park in Seabrook. The NHC reports almost 3 million people lost power, 2.7 million of them in southeastern Texas.
Ike, September 13, 2008. A Category 2 at landfall on Galveston Island. The NHC report cites an insured damage estimate of about $12.5 billion across Texas, Louisiana and Arkansas, not counting inland flooding or storm surge, and notes that large pieces of the retractable roof at Reliant Stadium were torn off.
FM Global’s loss engineers make the same point from the other side: even a storm rated Category 4 at landfall may deliver Category 1 or 2 winds at a given facility, and lower winds still damage roofs whose design, installation or maintenance is deficient.
Sources: NHC Beryl report; NWS Houston/Galveston Beryl report; NHC Ike report; NHC Harvey report; FM Global P0283.
Why roofs fail below design wind
The edge goes first. Then the rest follows.
Code design winds are rare by intent. Roof damage is not. The research points to the same place every time: perimeter flashing, coping, and corners.
Chart 4
Low-slope roofs get damaged long before the code wind arrives.
IBHS studied 177 light commercial low-slope roofs after Hurricane Ian. It then estimated how rare a wind event has to be to give a 25%, 50% or 75% chance of damage. Compare that with the events the building code designs for.
View the data
| Roof type | 25% chance of damage | 50% | 75% |
|---|---|---|---|
| Low-slope membrane | 1 in 30 | 1 in 50 | 1 in 100 |
| Low-slope built-up | 1 in 20 | 1 in 30 | 1 in 75 |
IBHS assessed 177 light commercial low-slope roofs after Hurricane Ian in 2022. Membrane and built-up roofs had damage rates above 50%. Of the damaged low-slope roofs, 71% also had visible flashing or coping damage, including buildings built after Florida added ES-1 edge requirements.
FM Global’s own loss history points the same way: its insured wind losses averaged US$400 million a year from 1998 to 2007, and 80 percent of those loss dollars were related to roofing system failures.
FM’s engineering explains why edges matter so much. Uplift at roof corners can be more than two and a half times the uplift in the field of the roof, and more than one and a half times at the perimeter. Most roofs are attached uniformly, so the corners and perimeter are where fasteners get overloaded and a roof starts to peel.
“Full-scale experiments at the IBHS Research Center have shown that flashing failures, at sub-design winds, can initiate damage on mechanically attached, single-ply membrane roofs.”
“Low-slope roofs continue to present challenges in windstorms. Despite the development of new standards for materials and installation and continual code improvements, there has been little improvement in overall performance and little reduction in the frequency of damage to these roof systems.”
The same white paper reports that in IBHS full-scale tests, measured loads on edge flashing exceeded ASCE 7-22 values for 70% of wind directions on the roof flange and for 100% on the wall flange and hem. It also notes that losing a single fastener raises the load on the fasteners next to it by 50 percent. Small failures cascade.
“Protecting commercial roofing systems is the single-most effective way to reduce windstorm loss.”
Sources: IBHS Hurricane Ian report, Sept 2023; RICOWI/IBHS white paper via Metal Construction News, Feb 10, 2025; FM Global P0283. IBHS findings come from Southwest Florida and are cited for building behavior, not Texas wind climate.
The insurance picture
TWIA is growing. Private property rates are falling.
Two trends are running at once on the coast in 2026, and both reward a well-documented roof.
Chart 5
TWIA’s exposure has more than doubled since 2020.
The state’s windstorm insurer of last resort carried $55.0 billion of insured value at the end of 2020 and $127.1 billion by March 31, 2026.
View the data
| Year | Policies | Exposure |
|---|---|---|
| 2016 | 254,346 | $73.4B |
| 2017 | 231,567 | $65.0B |
| 2018 | 202,208 | $58.0B |
| 2019 | 189,203 | $55.2B |
| 2020 | 184,890 | $55.0B |
| 2021 | 193,002 | $59.5B |
| 2022 | 222,480 | $75.7B |
| 2023 | 247,531 | $95.7B |
| 2024 | 272,567 | $113.7B |
| 2025 | 284,846 | $126.5B |
| Q1 2026 | 286,251 | $127.1B |
TWIA: bigger, but capped for commercial buildings
TWIA insured 286,251 properties with $127.1 billion of insured value as of March 31, 2026. Galveston County alone held $42.3 billion, about a third of the total. Commercial and governmental policies numbered 7,904 with $11.3 billion of exposure, and TDI’s figures show commercial liability falling from $12.78 billion at the end of 2024 to $11.05 billion at mid-2026.
The commercial ceiling is the number to know. TWIA’s maximum limit for a commercial structure and its contents is $4,424,000, and only 2.4% of commercial policies are insured to that maximum. The average non-residential policy is $702,026. For a large plant, warehouse, or campus building, TWIA alone will not cover a total loss, so private wind coverage, and private underwriting standards, come into play.
Beryl tested the system at Category 1 strength. By October 25, 2024, TWIA had received 31,383 claims and paid $268.3 million on them, plus $74.9 million on Texas FAIR Plan claims.
The private market: softer, but not blind
Marsh reports US property insurance rates fell 13% in the second quarter of 2026, the eighth straight quarterly decline. The Council of Insurance Agents & Brokers reports commercial property premiums down 6.3% on average in the same quarter, and respondents also reported higher sublimits and lower deductibles, especially for wind and hail.
“loss-affected accounts and those with less comprehensive risk management data continued to see more differentiated outcomes.”
Our viewA softer market is a window, not a guarantee. Insurers still price a building on what they can verify: a WPI-8 on file, an engineered wind design, product approvals, and photos of the edge metal. The time to assemble that file is before renewal and before the next storm, not after a claim.
Sources: TWIA Fact Book, Q1 2026; TDI TWIA overview; TWIA Beryl update, Oct 30, 2024; Marsh US rates, Q2 2026; CIAB Q2 2026 P&C Market Survey, Aug 18, 2026. Rate changes are national averages for each firm’s book and will differ by building and location.
Warranty wind limits
What a manufacturer’s guarantee does and does not cover.
A roof warranty is a promise about leaks, within limits. It is not wind insurance. On the coast, the wind limit is the line to read first.
Standard wind: 55 mph
GAF’s single-ply guarantee matrix covers leaks from winds up to 55 mph as standard. Higher wind coverage, with listed options up to 120 mph, is available for purchase on select systems with GAF’s advance written approval.
100 mph and up: edge metal
For wind coverage of 100 mph or more, GAF requires its approved perimeter edge metal. The warranty and the research agree on where the roof is most exposed.
Hail, punctures, long terms
Hail and punctures are not covered unless purchased. Guarantee terms longer than 20 years require a new roof with a complete tear-off.
Mammoth Services is a 2026 GAF GoldElite Commercial Contractor and is eligible to offer GAF’s Diamond Pledge NDL, System Pledge, and Integrated System Limited Warranty on qualified projects. GAF sets eligibility, terms, and coverage, so no specific coverage is promised until GAF requirements are met. Manufacturer warranties also do not, by themselves, show compliance with FM ratings or building codes; those are separate checks.
Sources: GAF Single-Ply Guarantee Coverage Matrix COMEG858 V5.1, effective Jan 6, 2025; GAF commercial guarantees; Building Enclosure, Feb 2012. Verify Mammoth on GAF.com.
Windstorm checklist
Ten questions to settle before the first square comes off.
Use this with your engineer, your broker, and your roofer. Every item ties back to a source on this page.
- Is the building in TDI’s catastrophe area?Check the county, and in Harris County, which side of SH 146 and which city.
- What is the risk category and design wind speed?Get the address-specific value from the engineer of record or the city.
- Is TWIA coverage in play now or later?If yes, the WPI-1 goes in before work starts and inspections are scheduled during the work.
- Does the insurer require FM standards?Ask the broker. If the site is FM Global insured, involve FM before ordering material.
- What wind does the warranty cover?Match the guarantee’s wind limit to the risk, and know what it takes to buy more.
- How is the edge metal tested and attached?Ask for ES-1 tested edge systems and the attachment at perimeters and corners.
- Replace or recover?Replacement goes to the deck. A recover has to meet the conditions in IBC 1512.3, and long warranty terms require a tear-off.
- What is the deck, and how is it secured?Deck type and attachment drive uplift resistance. A tear-off is the time to verify it.
- Are rooftop units and openings ready for wind?Secure curbs and equipment, and have the designer account for unprotected glazing that could break.
- Where will the paperwork live?Keep the WPI-8, wind design, product approvals, warranty, and edge photos together for renewals, claims, and sale.
Want this checklist walked on your own roof? Book a roof assessment or call (832) 416-1566.
Questions
Texas windstorm requirements: direct answers.
If your question is not here, call Mammoth Services at (832) 416-1566.
- 01
What are the windstorm requirements for a commercial roof in Texas?
On the Texas Gulf Coast, a commercial roof answers to four sets of wind requirements. The building code sets the design wind speed (the 2024 IBC with ASCE 7-22 in TDI’s windstorm program since April 1, 2026). TDI’s windstorm certificate (WPI-8) is needed for TWIA insurance in the designated catastrophe area. An FM Global rating applies if your insurer requires it. The manufacturer’s warranty has its own wind limit. Each one is a different number, measured a different way.
- 02
Does a commercial re-roof need a TDI windstorm inspection?
If the building is in TDI’s designated catastrophe area and will be insured through TWIA, yes. TDI says new structures, alterations, additions and repairs, including re-roofs and roof repairs, must be built and inspected to TDI’s adopted code to qualify. File Form WPI-1 before work starts, and TDI inspects while the work is in progress. Some minor non-structural repairs are exempt; TDI publishes that list.
- 03
What wind speed does a commercial roof need to meet near Houston and Galveston?
It depends on the address and the building’s risk category. Published local values include 137, 146, 156 and 163 mph for Risk Categories I to IV in Santa Fe, 145 mph in League City, and 150 mph citywide in Seabrook. The City of Houston requires a site-specific lookup. TDI points owners to tools such as the ASCE 7 Hazard Tool, and the engineer of record confirms the number.
- 04
Is an FM 1-90 rating the same as 90 mph?
No. An FM Approvals rating such as Class 1-90 refers to an uplift pressure in pounds per square foot that the tested roof assembly resisted, not a wind speed. FM also applies a safety factor, so a 1-90 assembly is not automatically right for a building whose design wind speed is 90 mph or for one whose calculated uplift is 90 psf.
- 05
Does a roof warranty cover hurricane wind damage?
Usually only up to a stated wind speed. GAF’s single-ply guarantee matrix, for example, covers leaks from winds up to 55 mph as standard, with higher wind coverage, up to 120 mph on select systems, available for purchase with GAF’s advance approval. A warranty is not insurance, so read the guarantee’s own wind wording and your property policy together.
- 06
What happens if a roof was replaced without a TDI windstorm inspection?
TDI says that if a re-roof or repair was completed without an inspection, an appointed Texas licensed professional engineer must perform a post-construction inspection. That usually means opening up work for the engineer to see. Texas law also says a WPI-1 filed late may keep a WPI-8 from being issued unless plans, calculations and other documentation are submitted, so plan the inspection before the first square is torn off.
- 07
Did Texas windstorm requirements change in 2026?
Yes. Starting April 1, 2026, TDI requires windstorm Certificate of Compliance applications (WPI-1) to be certified to the 2024 International Building Code or the 2024 International Residential Code. The designated catastrophe areas did not change, but TDI says most of them are now inside the windborne debris region.
- 08
Are Webster, Nassau Bay and Clear Lake in the TDI windstorm area?
No. In Harris County, TDI’s windstorm program covers only areas east of State Highway 146 inside the city limits of La Porte, Morgan’s Point, Pasadena, Seabrook and Shoreacres. Webster, Nassau Bay and Houston’s Clear Lake area are outside it, so a WPI-8 is not a TWIA requirement there, but city codes and the design wind speed still apply. All of Galveston County is inside the program.
Sources
Where every number comes from.
Public sources only, checked October 7, 2026. Code sections refer to the 2024 IBC as adopted for TDI’s windstorm program. This guide is general information, not engineering, legal, or insurance advice.
- Texas Department of Insurance (TDI), Adopted Building Codes, accessed Oct 7, 2026
- TDI, General questions about windstorm, accessed Oct 7, 2026
- TDI, What is the Windstorm Inspection Process?, last updated Jul 21, 2025
- TWIA Insurability Requirements, hosted by TDI (2013), citing Texas Insurance Code Sec. 2210.251(c)
- TDI, Harris County designated catastrophe area map
- TDI, Galveston County designated catastrophe area map
- 2024 IBC as adopted for the TDI windstorm program, Chapter 15 (UpCodes), Sections 1504.4, 1504.6 and 1512
- 2024 IBC as adopted for the TDI windstorm program, Chapter 16 (UpCodes), Section 1609.3 and Figures 1609.3(1) to (4)
- Thomas L. Smith, “A revised approach to wind load calculations,” Professional Roofing (NRCA), May 1, 2023
- City of Santa Fe, Frequently Asked Questions, rev. 5, 2023
- City of League City, Commercial SOP and Pre-Con Packet
- City of Seabrook, Code of Ordinances Secs. 18-121 and 18-122 (Municode)
- Houston Permitting Center, wind speed and code guidance document (media 7101)
- NOAA AOML Hurricane Research Division, Continental United States Hurricane Impacts/Landfalls 1851-2025
- NOAA NCEI, Billion-Dollar Weather and Climate Disasters, events 1980-2024 (CPI-adjusted CSV, archived)
- NOAA National Hurricane Center, Tropical Cyclone Report: Hurricane Beryl (Beven, Fritz, Alaka), May 1, 2025
- NWS Houston/Galveston, Post-Tropical Cyclone Report and impact narratives, Beryl, Jul 12, 2024
- NOAA National Hurricane Center, Tropical Cyclone Report: Hurricane Ike (Berg), Jan 23, 2009, updated 2014
- NOAA National Hurricane Center, Tropical Cyclone Report: Hurricane Harvey
- IBHS, Building Performance during Hurricane Ian, Part I (Giammanco, Newby, Pogorzelski), Sept 2023
- Metal Construction News, “Low-slope roofs and Hurricane Ian” (RICOWI and IBHS white paper), Feb 10, 2025
- FM Global, Protecting Roofing Systems Against Windstorm Damage (P0283, rev. 10/2015)
- Stan Choiniere, “Understanding Wind Uplift Ratings,” Building Enclosure, Feb 13, 2012
- TWIA, Fact Book, data as of Q1 2026
- TDI, TWIA overview (direct liability by policy type)
- TWIA, Hurricane Beryl response update, Oct 30, 2024
- The Council of Insurance Agents & Brokers, Q2 2026 P&C Market Survey, Aug 18, 2026
- Marsh, US Insurance Market Rates, Global Insurance Market Index, Q2 2026
- GAF, Single-Ply Guarantee Coverage Matrix COMEG858, V5.1, effective Jan 6, 2025
- GAF, Commercial roofing guarantees
Next step
Planning roof work on the coast?
Book a roof assessment and Mammoth Services will start with your building: its location on TDI’s map, its design wind speed, its edges, and how your operation runs. Prefer to talk first? Book a roof assessment call.