By The Roofing Brief Team. Last reviewed: October 2026.
A roof wind uplift rating is the uplift pressure, in pounds per square foot (psf), that a tested roof assembly held in a laboratory, not a wind speed. FM 1-90 means the assembly held 90 psf for 60 seconds, UL 580 Class 90 means it survived a test sequence that peaks at 105 psf, and ASTM D7158 Class H means an asphalt shingle is accepted where the mapped ultimate design wind speed is up to 194 mph. To know whether a rating is enough, you convert your site wind speed into a zone pressure with ASCE 7 and compare it to the rating after a 2.0 safety factor.
Roof wind uplift rating: key numbers at a glance
Six figures, from the FM 15 psf rating steps to the UL 105 psf Class 90 peak, settle most specification arguments about uplift. Each one comes from the standard, data sheet or code section named in the Source column, and each is checkable against that document.
| Figure | Value | Source |
|---|---|---|
| FM 1-90 tested pressure and design pressure | 90 psf held for 60 s; suits 45 psf design pressure (safety factor 2.0) | FM Data Sheet 1-52 (Feb 2020, rev. Oct 2024) |
| Lowest FM rating and step size | 1-60, then 15 psf steps (1-75, 1-90, 1-105…) | FM Data Sheet 1-52, Table 2.2.5-2 note 1 |
| UL 580 Class 90 pressures | Nominal 90 psf static, 66 to 90 psf oscillating, 105 psf maximum static | UL Code Authority, Table 1 |
| Florida margin on any uplift test result | 2:1, unless the test standard sets its own | FBC Building 1504.9 (8th Ed., 2023) |
| Field uplift test passing pressure | 1.25 x design wind pressure, held 1 minute | FM Data Sheet 1-52, Section 2.2.4 |
| Asphalt shingle class at the top of the IRC table | ASTM D7158 Class H, accepted to Vult 194 mph | 2021 IRC Table R905.2.4.1 |
What a roof wind uplift rating measures
Wind flowing over a roof lowers the pressure above it while air leaking into the building raises the pressure below it, and the difference pulls the covering upward. Every rating discussed here reports how many psf of that net upward pressure a specific assembly resisted: deck, insulation, membrane or panel, fasteners and spacing together. Change the deck gauge or the clip spacing and the number no longer applies, which is why FM 4474 and UL 580 listings are written for named assemblies.
The mph confusion has a documented origin. A 2026 FM approval overview from Seaman Corporation, maker of FiberTite, explains that the old I-60 class came from an 88 mph wind at about 33 ft, roughly 20 psf of velocity pressure, times a 1.5 roof shape factor (30 psf) times a safety factor of 2, giving 60 psf. I-90 started from a 110 mph wind: 30 psf x 1.5 x 2 = 90 psf. The rating number was always a pressure; the wind speed was only the starting assumption.
| Original FM class | Assumed wind speed | Velocity pressure (0.00256 x V squared) | x 1.5 shape factor | x 2.0 safety factor = test pressure |
|---|---|---|---|---|
| I-60 (now 1-60) | 88 mph | 19.8 psf (about 20) | 30 psf | 60 psf |
| I-90 (now 1-90) | 110 mph | 31.0 psf (about 30) | 45 psf | 90 psf |
Source: Seaman Corporation, FiberTite FM Approval Overview (2026), which describes the derivation; velocity pressure recomputed by The Roofing Brief with the standard 0.00256 x V squared constant. Modern ratings no longer map to any single wind speed.
Roof wind uplift rating chart: what each class number means
Each test standard uses a different scale, so “90” on one document and “Class H” on another cannot be compared without converting. FM and UL numbers are pressures, ASTM D3161 classes are fan speeds, and ASTM D7158 classes are tied to code wind speeds. The chart below puts every common rating into the same terms.
| Rating | What the number is | How it is earned | Design pressure it supports | Source |
|---|---|---|---|---|
| FM 1-60, 1-75, 1-90, 1-105, 1-120 and up | Uplift pressure in psf held by the full assembly | ANSI/FM 4474: pressure raised in 15 psf steps, each held 60 s; rating is the last step held | Rating divided by 2.0: 1-60 = 30 psf, 1-75 = 37.5, 1-90 = 45, 1-120 = 60 | FM DS 1-52; FiberTite overview |
| UL 580 Class 15, 30, 60, 90 | Nominal static stage in psf | 10 ft x 10 ft specimen, 5 min static plus 60 min oscillating at a 10 s cycle per class; not run to failure | Class 90 maximum static is 105 psf, which at a 2:1 margin is 52.5 psf | UL; ATAS Tech Tips |
| UL 1897 result (for example 120 psf) | Highest psf held before failure | Static differential pressure on the covering and its attachment, run to failure | Tested psf divided by 2 under FBC 1504.9 | UL; ATAS |
| ASTM E1592 load table | psf at failure for each tested span | Uniform static pressure on metal panels 0.012 to 0.050 in thick, deflection read at 6 or more points | Allowable load after the code or AISI safety factor; read the table, not one number | ATAS Tech Tips |
| ASTM D3161 Class A, D, F | Fan wind speed: 60, 90, 110 mph | 2-hour fan stream across a 2:12 test deck | Code table limits by Vult; F is the only class above Vult 129 mph | IRC Table R905.2.4.1 |
| ASTM D7158 Class D, G, H | Code wind speed ceiling: Vult 116, 155, 194 mph | Measured seal strength vs calculated uplift force | Exposure B or C, mean roof height 60 ft or less | IRC Table R905.2.4.1 |
UL 580 publishes its stage pressures in a table, and the UL Code Authority summary shows the full sequence. An assembly rated Class 90 has passed Class 30, 60 and 90 stages in order on the same 10 ft by 10 ft specimen.
| UL 580 class | Nominal static uplift (psf) | Oscillating range (psf) | Maximum static uplift (psf) | Allowable at a 2:1 margin (psf) |
|---|---|---|---|---|
| 15 | 15 | 11 to 21 | 23 | 11.5 |
| 30 | 30 | 22 to 42 | 45 | 22.5 |
| 60 | 60 | 44 to 83 | 75 | 37.5 |
| 90 | 90 | 66 to 90 | 105 | 52.5 |
Source: UL, “Certifying Roof Deck Constructions for Wind Resistance,” Table 1. The last column is Roofing Brief arithmetic (maximum static divided by 2) to show how a Florida-style 2:1 margin reads; a product approval may state its own allowable value. ATAS notes that over a solid deck the covering itself resists only the 56.5 psf vacuum portion of the Class 90 test.
Which uplift test applies to your roof type
The building code, not the manufacturer, decides which tests count. Since the 2021 edition the IBC lists them under Section 1504.4, and the 2024 IRC repeats the metal panel rules in R905.10.5. Florida keeps its own numbering and adds Testing Application Standards (TAS) inside the High-Velocity Hurricane Zone.
| Roof type | Accepted uplift tests | Code section | Source |
|---|---|---|---|
| Built-up, modified bitumen, single-ply, membrane and metal panels over a solid deck | FM 4474, UL 580 or UL 1897 | IBC 1504.4.1 (2021, 2024); 1504.3.1 in the 2018 IBC | ICC, 2024 IBC Ch. 15 |
| Structural standing seam metal (no deck) | ASTM E1592 or FM 4474 | IBC 1504.4.2; IRC R905.10.5 | ICC, 2024 IRC Ch. 9 |
| Structural through-fastened metal (no deck) | ASTM E1592, FM 4474 or UL 580 | IBC 1504.4.2; IRC R905.10.5 | NRCA, Professional Roofing, Oct 2025 |
| Metal roof shingles, including stone-coated steel | ASTM D3161, FM 4474, UL 580 or UL 1897 | IBC 1504.4.3 | ICC, 2024 IBC Ch. 15 |
| Asphalt shingles | ASTM D7158 (D3161 for products outside its scope) | IRC R905.2.4.1 | our ASTM D3161 vs D7158 guide |
| Ballasted single-ply | No uplift test; designed to ANSI/SPRI RP-4 | IBC 1504 (ballast provisions) | NRCA, Oct 2025 |
| Florida metal panels | UL 580, ASTM E1592 or TAS 125 | FBC Building 1504.3.2 (8th Ed., 2023) | UpCodes, FBC 1504 |
NRCA’s October 2025 Professional Roofing article adds a point most spec writers miss: the IBC does not require testing at FM or UL Solutions themselves, so results from another recognized laboratory using the FM 4474 or UL methods are acceptable. That is why manufacturer tables often cite Intertek or other labs next to an FM or UL method number. For how the attachment method changes the tested number on a membrane roof, see our membrane attachment methods comparison.
How to calculate the wind uplift on a roof
Uplift design pressure comes from ASCE 7, which the 2024 IBC references in its 2022 edition (ASCE 7-22) and the 2021 IBC in its 2016 edition. The one change that trips up older spreadsheets is that ASCE 7-22 moved the directionality factor Kd out of the velocity pressure equation and into the pressure equations, per Carlisle SynTec’s March 2025 comparison. The arithmetic result is the same if you apply Kd once.
- Find the basic wind speed V for the address and Risk Category on the ASCE Hazard Tool. Most houses and ordinary commercial buildings are Risk Category II.
- Pick the exposure (B suburban, C open terrain, D open water) and read Kz at the mean roof height from ASCE 7-22 Table 26.10-1: at 30 ft, Kz is 0.70 in Exposure B, 0.98 in C and 1.16 in D.
- Compute velocity pressure qh = 0.00256 x Kz x Kzt x Ke x V squared. Kzt is 1.0 without a hill or escarpment, and Ke is 1.0 at sea level. At 140 mph, Exposure C and 30 ft, this gives 49.2 psf.
- Multiply by Kd = 0.85 and by 0.6 to convert the strength-level load to allowable stress design (ASD), the basis manufacturers usually publish.
- Multiply by each zone’s coefficient sum. For enclosed roofs 60 ft or lower with slopes of 7 degrees or less at a 10 sq ft effective area, Carlisle lists GCp of 0.9 (zone 1′), 1.7 (zone 1), 2.3 (zone 2) and 3.2 (zone 3) acting upward, plus internal pressure GCpi of 0.18.
- Multiply each zone pressure by 2.0 to get the minimum tested rating, then round up to the next 15 psf FM step (minimum 1-60) if you are matching FM ratings.
Worked example: a 30 ft tall, enclosed flat-roof building in Exposure C where the ASCE Hazard Tool returns 140 mph. Every line below can be rechecked with a calculator.
| Step | Arithmetic | Result |
|---|---|---|
| Velocity pressure | 0.00256 x 0.98 x 1.0 x 1.0 x 140 squared | 49.2 psf |
| Apply Kd and ASD | 49.2 x 0.85 x 0.6 | 25.1 psf |
| Zone 1′ (interior field) | 25.1 x (0.9 + 0.18) | 27.1 psf, needs 54.2 psf tested: FM 1-60 |
| Zone 1 (field) | 25.1 x (1.7 + 0.18) | 47.1 psf, needs 94.3 psf tested: FM 1-105 |
| Zone 2 (perimeter) | 25.1 x (2.3 + 0.18) | 62.2 psf, needs 124.4 psf tested: FM 1-135 |
| Zone 3 (corner) | 25.1 x (3.2 + 0.18) | 84.8 psf, needs 169.5 psf tested: FM 1-180 |
| Check against UL 580 Class 90 | 105 psf maximum static / 2 = 52.5 psf | Covers zones 1′ and 1 only |
Roofing Brief calculation from ASCE 7-22 Eq. 26.10-1, Table 26.10-1 (Kz) and the Figure 30.3-2A coefficients as listed by Carlisle SynTec (2025). Assumes Risk Category II, Kzt = 1.0, Ke = 1.0. Use a design professional’s calculation for permits; zone widths and partially enclosed buildings change the result.
The example exposes the most common specification error: a project specified as “FM 1-90” at 140 mph in Exposure C falls 4.3 psf short in the field (90 tested vs 94.3 needed) before the perimeter and corners are even considered. FM Data Sheet 1-52 states the same factor in its own words: “The minimum FM Approved roof assembly rating is based upon a factor of safety of 2 over the design wind pressure.”
Wind speed to required rating: low-slope roof uplift chart
The two charts below run the same six-step method across the wind speeds on the ASCE 7-22 Risk Category II map, so a reader can find the row for a site and see the zone pressures and the FM rating each zone needs. Exposure B covers most suburban sites; Exposure C covers open terrain, airports and most coastal fringes.
| Vult (mph) | Zone 1 field (psf) | Zone 2 perimeter (psf) | Zone 3 corner (psf) | Minimum FM rating, zones 1 / 2 / 3 |
|---|---|---|---|---|
| 105 mph | 18.9 | 25.0 | 34.1 | 1-60 / 1-60 / 1-75 |
| 115 mph | 22.7 | 30.0 | 40.9 | 1-60 / 1-60 / 1-90 |
| 130 mph | 29.0 | 38.3 | 52.2 | 1-60 / 1-90 / 1-105 |
| 140 mph | 33.7 | 44.4 | 60.5 | 1-75 / 1-90 / 1-135 |
| 150 mph | 38.7 | 51.0 | 69.5 | 1-90 / 1-105 / 1-150 |
| 160 mph | 44.0 | 58.0 | 79.1 | 1-90 / 1-120 / 1-165 |
| 170 mph | 49.7 | 65.5 | 89.3 | 1-105 / 1-135 / 1-180 |
| 180 mph | 55.7 | 73.4 | 100.1 | 1-120 / 1-150 / 1-210 |
Exposure B, mean roof height 30 ft (Kz 0.70), enclosed, slope 7 degrees or less, 10 sq ft effective area, ASD. Roofing Brief calculation; FM ratings use a 2.0 factor and 15 psf steps with a 1-60 floor.
| Vult (mph) | Zone 1 field (psf) | Zone 2 perimeter (psf) | Zone 3 corner (psf) | Minimum FM rating, zones 1 / 2 / 3 |
|---|---|---|---|---|
| 105 mph | 26.5 | 35.0 | 47.7 | 1-60 / 1-75 / 1-105 |
| 115 mph | 31.8 | 42.0 | 57.2 | 1-75 / 1-90 / 1-120 |
| 130 mph | 40.7 | 53.6 | 73.1 | 1-90 / 1-120 / 1-150 |
| 140 mph | 47.1 | 62.2 | 84.8 | 1-105 / 1-135 / 1-180 |
| 150 mph | 54.1 | 71.4 | 97.3 | 1-120 / 1-150 / 1-195 |
| 160 mph | 61.6 | 81.2 | 110.7 | 1-135 / 1-165 / 1-225 |
| 170 mph | 69.5 | 91.7 | 125.0 | 1-150 / 1-195 / 1-255 |
| 180 mph | 77.9 | 102.8 | 140.1 | 1-165 / 1-210 / 1-285 |
Exposure C, mean roof height 30 ft (Kz 0.98); same assumptions as the Exposure B chart. FM Global-insured buildings must use FM Data Sheet 1-28 through RoofNav, which applies its own factors (FM’s worked example in DS 1-52 uses an importance factor of 1.15), so FM’s required rating can exceed these figures.
Two patterns stand out. In Exposure B, an FM 1-60 field rating holds up to 130 mph, while in Exposure C it stops below 115 mph. And corners need roughly 1.8 times the field rating in every row, because the zone 3 coefficient sum (3.38) is 1.8 times the zone 1 sum (1.88). FM Data Sheet 1-29’s prescriptive alternative handles that gap with extra fastening: NRCA summarizes it as at least 50% more attachment at the perimeter and at least double at the corners.
Why FM 1-90 is not a 90 mph roof
Shorthand that circulates in spec sections, forum threads and sales sheets often turns a pressure rating into a wind speed, reading FM 1-90 as a 90 mph roof. The primary documents say otherwise, and the table sets each common shorthand next to what the test standard or data sheet actually states.
| Common shorthand | What the primary document says | Source |
|---|---|---|
| “FM 1-90 means a 90 mph roof” | The 90 is psf held in the FM 4474 test; with a 2.0 factor, 1-90 suits 45 psf of design pressure in zone 1 | FM DS 1-52, Section 3.1 |
| “UL 90 means it resisted 90 psf” | Class 90 includes a 90 psf nominal static stage but peaks at 105 psf maximum static, and the test stops there rather than running to failure | UL Table 1; ATAS |
| “UL class numbers are just test stage names” | Each class has published nominal, oscillating and maximum psf values | UL Table 1 |
| “A 1-90 spec covers the whole roof” | FM 1-90 describes the field; perimeter and corner zones need higher ratings or prescriptive enhancement | IIBEC Interface; NRCA |
| “A 130 mph shingle warranty is a wind rating” | A warranty speed is a contract term with installation conditions; the ASTM class is a separate lab classification | shingle wind warranties by brand |
Wind uplift calculators: NRCA, FM RoofNav and the ASCE Hazard Tool
Searches for a “roof wind uplift rating calculator” or an “FM Global wind uplift calculator” lead to five free tools that do different jobs. Only two of them output zone pressures, and only one outputs an FM rating.
| Tool | What it outputs | Basis | Use it when | Source |
|---|---|---|---|---|
| NRCA Roof Wind Designer | Zone design pressures plus minimum recommended design wind-resistance loads; edge metal (ES-1) and gutter (GT-1) capacities | ASCE 7-05, 7-10, 7-16 or 7-22; 1 mph speed steps since the December 2023 update | Any code-compliance roof design | roofwinddesigner.nrca.net |
| FM RoofNav Ratings Calculator | Zone pressures and the minimum FM Approved rating; links to approved assemblies | FM Data Sheet 1-28 | The building is insured by FM Global or the spec names FM | roofnav.com |
| ASCE Hazard Tool | Site basic wind speed by Risk Category; no roof pressures | ASCE 7 maps | Step 1 of any calculation | ascehazardtool.org |
| UL Product iQ | UL 580 roof deck constructions (TGKX) and UL 1897 roofing systems (TGIK) | UL listings | Checking a UL construction number | productiq.ulprospector.com |
| DORA Directory of Roof Assemblies | Assemblies tested by third-party labs | Manufacturer-submitted test data | Finding a non-FM tested assembly | dora-directory.com |
How to read a product approval or uplift listing
A rating only applies to the assembly printed on the approval: a 1-90 listing on a 22 gauge steel deck says nothing about the same membrane on wood. Before accepting a submittal, check these seven items against the document, in this order.
- Identify the document type: an FM RoofNav assembly number, a UL construction number (UL’s own example is “Construction No. 355”), a Florida Product Approval FL number, or a Miami-Dade NOA. Each lists a different kind of number.
- Confirm whether the psf value is a tested result or an allowable load. FBC 1504.9 applies a 2:1 margin to test results unless the standard sets its own, so a 120 psf UL 1897 result supports 60 psf of design pressure, and a metal supplier’s catalog can mix allowable loads (factor of safety 2.0 applied) with maximum design pressures.
- Match the deck. FM-approved decks include steel of 22 gauge and heavier, structural concrete of at least 2,500 psi and wood of at least 3/4 in fire-retardant-treated plywood, per 2012 summaries of FM requirements by Conspectus and Building Enclosure; 1/2 in plywood does not qualify for FM.
- Match fastener or clip spacing, panel gauge and width. Tested spacing is a maximum: 24 in o.c. clips may be installed at 12 in, never at 30 in, and a 24 gauge test does not cover a 26 gauge panel.
- Compare the listed pressure with the highest zone it will sit in. A zone 1 rating used across a whole roof needs perimeter and corner enhancements under FM Data Sheet 1-29.
- For Florida, check the code edition and the HVHZ flags on the Florida Product Approval search. The 8th Edition (2023) has been in force since December 31, 2023, and the 9th Edition (2026) takes effect December 31, 2026, so approvals may be revised.
- Check the approval date or revision letter, and reject documents that list a superseded test standard edition without a current revision.
Inside Miami-Dade and Broward counties the rules tighten again, with TAS 100, TAS 110 and TAS 125 for metal and a 1.45:1 margin on in-situ tests under FBC 1523.4. Our Miami-Dade NOA roofing approval guide covers how to read the NOA limitations page. Worked FL approval values for exposed-fastener panels, including one approval listing 52.5 psf or 63.5 psf depending on the anchor pattern, sit on our 5V metal roofing page.
Field verification: FM 1-52 uplift tests on a finished roof
A lab rating proves the design; a field uplift test checks the installation. FM Data Sheet 1-52 (February 2020, interim revision October 2024) sets the passing pressure at 1.25 times the design wind pressure in each zone, held for one minute without separation. The table converts common FM ratings into the pressures a field test must reach on a low-slope roof.
| Required FM rating (zone 1) | Field test pressure, zone 1 (psf) | Field test pressure, zone 2 (psf) | Field test pressure, zone 3 (psf) |
|---|---|---|---|
| 1-60 | 38 | 49 | 67 |
| 1-75 | 47 | 62 | 84 |
| 1-90 | 56 | 74 | 101 |
| 1-105 | 66 | 87 | 118 |
| 1-120 | 75 | 99 | 135 |
| 1-150 | 94 | 124 | 169 |
Source: FM Data Sheet 1-52, Table 2.2.5-1, for enclosed buildings with low-slope gable roofs (under 1.5:12) and eave heights of 60 ft or less. The negative pressure test raises pressure in 7.5 psf increments held 1 minute each (Appendix D.3.2.7).
FM Data Sheet 1-52 also warns that uplift testing “does not accurately evaluate the uplift resistance of the roof deck or edge securement,” and names lifting metal edge flashing and coping, followed by progressive membrane peeling, as the most common cause of membrane loss. Edge metal is rated separately under ANSI/SPRI ES-1, which NRCA’s Roof Wind Designer also reports.
Which roof wind uplift rating to specify
The decision table maps the most common situations to the rating that satisfies code or insurer rules. Wind speeds are ultimate (Vult) values from the ASCE Hazard Tool; where a row cites a code table, the local edition and any amendments govern.
| Your situation | Rating to require | Rule or source |
|---|---|---|
| Asphalt shingles, Vult up to 116 mph | ASTM D7158 Class D, G or H, or D3161 Class A, D or F | IRC Table R905.2.4.1 |
| Asphalt shingles, Vult 129 mph | D7158 Class G or H, or D3161 Class A, D or F | IRC Table R905.2.4.1 |
| Asphalt shingles, Vult 142 to 155 mph | D7158 Class G or H, or D3161 Class F | IRC Table R905.2.4.1 |
| Asphalt shingles, Vult 168 to 194 mph | D7158 Class H, or D3161 Class F | IRC Table R905.2.4.1 |
| Metal panels over a solid deck on a house | FM 4474, UL 580 or UL 1897 assembly whose allowable psf meets the R301.2.1(1) zone loads | 2024 IRC R905.10.5 |
| Structural standing seam over purlins | ASTM E1592 or FM 4474 load table at your purlin span | IBC 1504.4.2 |
| Commercial low-slope, not FM-insured | Tested assembly at 2.0 x ASD zone pressure (or 1.25 x strength-level pressure) | IBC 1504.4.1; NRCA, Oct 2025 |
| Building insured by FM Global | RoofNav assembly at the DS 1-28 rating, plus DS 1-29 perimeter and corner enhancement | FM Data Sheets 1-28, 1-29 |
| Spec says “FM 1-90” at 140 mph, Exposure C, 30 ft | Field needs 1-105; ask the engineer of record to revise | Worked example above |
| Florida, outside the HVHZ | Florida Product Approval psf at a 2:1 margin | FBC 1504.3.2, 1504.9 |
| Miami-Dade or Broward County | Miami-Dade NOA tested to TAS protocols | FBC 1523 |
For a house, the deck nailing behind the covering matters as much as the covering’s class: the IRC tightens sheathing fastening to 4 in on center in some high-wind areas. Our IRC roof deck fastening guide lists the Table R602.3(1) schedule. In Florida, the separate 25 percent reroof rule is explained in our 25% roofing rule by state page.
Frequently asked questions
What is a class 90 wind uplift rating?
A Class 90 wind uplift rating is the top classification in UL 580. A 10 ft by 10 ft roof assembly passes the Class 30, 60 and 90 stages, with a nominal static uplift of 90 psf, oscillating pressure of 66 to 90 psf for 60 minutes and a maximum static pressure of 105 psf. It is a pressure rating, not a 90 mph wind speed.
What is the 25% rule in roofing?
The 25% rule comes from Florida Building Code, Existing Building section 706.1.1: if more than 25 percent of a roof or roof section is repaired, replaced or recovered in 12 months, the whole roof covering must meet current code. Since 2022, Fla. Stat. 553.844(5) exempts roofs built under the 2007 Florida Building Code or later. Most other states have no statewide 25 percent trigger.
How do I calculate the wind uplift on a roof?
Under ASCE 7-22, find the site wind speed (V) on the ASCE Hazard Tool, compute velocity pressure as 0.00256 x Kz x Kzt x Ke x V squared, multiply by Kd 0.85 and 0.6 for allowable stress design, then multiply by each zone’s coefficient sum. A 140 mph, 30 ft, Exposure C flat roof works out to about 47 psf in the field and 85 psf in the corners.
What is a level 7 wind rating?
Level 7 usually refers to force 7 on the Beaufort wind scale, a near gale of 32 to 38 mph per the National Weather Service. It is not a roof uplift rating. For comparison, the lowest ASTM D3161 shingle class, Class A, is tested at a 60 mph fan stream, and roof assemblies are rated in psf, not Beaufort levels.
Does FM 1-90 mean a roof is rated for 90 mph winds?
No. FM 1-90 means the assembly held 90 psf of uplift for 60 seconds in the ANSI/FM 4474 test, and the 1 is the Class 1 fire rating. FM Data Sheet 1-52 applies a safety factor of 2.0, so a 1-90 assembly suits a design pressure of 45 psf. Historically, FM derived 1-90 from a 110 mph wind, which is where the mph confusion started.
Is there an FM Global wind uplift calculator?
Yes. FM Approvals’ RoofNav includes a Ratings Calculator that applies FM Data Sheet 1-28 to give zone pressures and the minimum FM Approved rating, and RoofNav also lists the approved assemblies. Buildings not insured by FM Global usually use ASCE 7 instead, and NRCA’s free Roof Wind Designer covers ASCE 7-05 through ASCE 7-22.
What wind uplift rating do I need for a 150 mph wind zone?
It depends on roof type and exposure, so calculate it. For a 30 ft, enclosed low-slope building in Exposure C at 150 mph (ASCE 7-22), the field design pressure is about 54 psf, which needs an FM 1-120 assembly, rising to 1-150 at the perimeter and 1-195 at the corners. Asphalt shingles at 155 mph need ASTM D7158 Class G or H.
Sources
- FM Property Loss Prevention Data Sheet 1-52, Field Verification of Roof Wind Uplift Resistance (Feb 2020, interim revision Oct 2024)
- UL, Certifying Roof Deck Constructions for Wind Resistance (Code Authority, Issue 2, 2010)
- ATAS International, Tech Tips: Wind Uplift (UL 580, UL 1897, ASTM E1592)
- Carlisle SynTec, Adjustments Between ASCE 7-16 and ASCE 7-22 (March 2025)
- ASCE 7-22 Table 26.10-1, Velocity Pressure Exposure Coefficients (ASCE Amplify)
- NRCA, Professional Roofing, Understanding wind design (October 2025)
- NRCA Roof Wind Designer
- Seaman Corporation, FiberTite FM Approval Information (2026)
- ICC, 2024 International Building Code, Chapter 15
- ICC, 2024 International Residential Code, Chapter 9
- Florida Building Code, Building, 8th Edition (2023), Section 1504.9 (UpCodes)
- IIBEC Interface, Roof Wind Load Design
- National Weather Service, Beaufort Wind Scale