Preparing Commercial Roofs for Severe Weather: High-Wind Lift & Hail Defense Strategies
Oct 12, 2026
Most storm damage on a commercial roof starts in predictable places. In high winds, failures usually begin at the corners and edges, where uplift is strongest. In hail, the weak points are worn membranes, soft insulation layers, and exposed rooftop equipment. Getting ready for severe weather means finding those weak points while the weather is calm and fixing them before a storm finds them first.
Want to make a clear decision about commercial roof repair in Columbus, OH? This guide explains how wind and hail actually damage low-slope roofs, what to check before storm season, which upgrades carry the most weight, and what to do in the first days after a storm.
How High Winds Lift a Low-Slope Roof
Wind does not push a flat roof down. It pulls it up. As air flows over and around a building, it changes direction and creates suction above the roof, much like the lift on an airplane wing. That suction is not spread evenly. ASCE 7, the national standard engineers use to calculate building design loads, divides a roof into field, perimeter, and corner zones because the edges take the strongest pull.
FM Global, a commercial property insurer that publishes widely used roofing engineering guidance, estimates that uplift at the corners can be more than two and a half times the force on the main interior of the roof, called the field. Along the perimeter edges, it can be more than one and a half times higher. Many roofs are fastened the same way from edge to edge, so the corners and perimeter often have the least extra holding power right where they need the most.
Wind speed also has an outsized effect. Pressure climbs with the square of wind speed, so a modest jump in speed creates a much larger load. FM Global notes that a 140 mph wind puts twice the uplift pressure on a roof as a 100 mph wind.
The Edge Metal Holds Everything Else Down
The metal edge flashing or coping that wraps the roof perimeter does more than finish the look. It anchors the roof cover to the building. FM Global calls it the most important component of the roofing system and warns that once wind loosens perimeter flashing, further damage to the roof cover and insulation is almost certain, even if those layers were properly attached. A loose edge gives wind a handle, and the membrane can peel back across a large area.
Openings and Rooftop Equipment Change the Pressure
The roof does not work alone. If wind or debris breaks windows or doors, air rushes inside and pushes up on the roof from below. FM Global estimates this can raise uplift on the roof by 10 to 30 percent. Rooftop units, vents, and panels that are not well secured can also break loose, tumble across the roof, and slice open the membrane.
How Hail Damages Commercial Roof Systems
The National Weather Service treats hail one inch across or larger, about the size of a quarter, as severe. At that size and up, hailstones can dent metal, crack aging membranes, and split flashing that is not backed by a solid surface.
Hail damage on a low-slope roof is often harder to spot than wind damage. Research presented at an ASTM roofing symposium, and summarized by the International Institute of Building Enclosure Consultants (IIBEC), found that hail can damage the layer under the membrane even when the membrane surface looks fine. In that testing, assemblies over lower-density insulation boards failed more often than those over gypsum boards, and adding a cover board improved performance every time. A cover board is a thin, rigid panel installed between the insulation and the membrane to give it a firmer base.
A few conditions tend to raise the odds of hail damage:
- Older, weathered membranes. FM Approvals’ toughest hail test adds 1,000 extra hours of heat aging to the roof cover before impact, which reflects how much sun and heat change roofing materials over time.
- Fastener plates directly under the membrane. Researchers flagged mechanically attached systems with plates right under the cover as a concern in severe hail areas, since the hard plate gives the membrane nothing to flex against.
- Soft insulation directly under the cover. Without a cover board, impacts can crush the insulation and leave the membrane unsupported.
- Unprotected rooftop equipment. Condenser coils, fans, and skylights take direct hits and can leak or stop working well.
What Recent Central Ohio Storms Show
Central Ohio does not need a hurricane to see roof-damaging winds. On June 29, 2012, a derecho, which is a long, fast-moving line of severe thunderstorms, raced across the region at more than 60 mph. The National Weather Service office in Wilmington, which covers Columbus, reported widespread significant wind damage across most of its forecast area, with gusts over 80 mph in a few locations.
The pattern repeated on August 11, 2026. The National Weather Service recorded an 82 mph gust at John Glenn Columbus International Airport and confirmed three EF1 tornadoes in Columbus, including one in South Columbus with estimated peak winds of 100 mph that damaged numerous trees and homes. Its damage surveys found that most of the destruction came from straight-line winds of 60 to 80 mph, with isolated spots reaching 90 to 100 mph.
A Pre-Storm Checklist for Commercial Roofs
The National Roofing Contractors Association (NRCA) recommends inspecting roof systems at least twice a year, preferably in spring and fall, with extra checks after hail, tornadoes, or other severe weather. A spring visit sets the roof up for summer storm season, and a fall visit catches summer wear before winter.
Use the table below as a walk-through guide:
| Area | What to Check | Why It Counts in Wind or Hail |
| Edge metal and coping | Loose sections, missing fasteners, gaps, rust at joints. FM Global suggests pulling gently on the lower edge; if it moves, it needs to be re-secured. | Loose edges are where wind peel-back usually starts. |
| Corners and perimeter membrane | Lifted seams, loose termination bars, wrinkles, backed-out fasteners | Uplift is highest in these zones. |
| Field of the roof | Blisters, splits, open seams, worn surfacing, soft spots underfoot | Weak or wet areas hold less in the wind and crack more easily under hail. |
| Rooftop equipment | Loose curbs or straps, missing access panel screws, damaged or missing hail guards | Loose units can tear the membrane, and unguarded coils can be damaged by hail. |
| Drains, scuppers, and gutters | Debris, loose strainers, standing water nearby | Blocked drainage adds weight and pushes water into weak spots. |
| Skylights and penetrations | Cracked domes, failed sealant, loose pipe boots and flashing | Hail and wind-driven rain often get in here first. |
| Loose items and trees | Leftover materials, displaced ballast, debris, overhanging branches | Anything loose can become a projectile in high wind. |
| Records | Roof age, system type, warranty terms, past repairs, dated photos | Clear records speed up repair decisions and insurance claims. |
Strengthening a Roof Against Wind Uplift
Wind upgrades work best when they target the zones that carry the highest loads. FM Global describes adding fasteners to the small perimeter and corner areas as one of the most cost-effective ways to upgrade an existing roof. For a 30-foot-tall building up to 100 feet wide, FM Global puts those zones at roughly the outer 10 feet of the roof, so much of the roof may not need extra work at all.
Re-Secure or Replace the Edge Metal
Loose flashing can often be re-fastened with weather-resistant fasteners and washers. When edge metal is damaged, undersized, or past its service life, replacement is the better call. IBHS recommends that edge flashing, coping, and counterflashing meet ANSI/SPRI/FM 4435/ES-1, a test standard for roof edge systems, at the wind pressures calculated for the building’s site.
Add Holding Power at the Corners and Perimeter
On single-ply roofs, IBHS recommends a perimeter “peel-stop,” such as a termination bar, set 1 to 2 feet in from the roof edge. Extra fasteners or added adhesive in the corner and perimeter zones can raise uplift resistance where it is needed. On mechanically attached membranes over steel decks, IBHS recommends running the sheets and fasteners across the deck ribs rather than along them.
Anchor Rooftop Equipment and Remove Loose Items
IBHS recommends that rooftop units and other equipment be attached to resist specific wind loads, with an added margin of safety. In practice, that means checking curbs, straps, and access panels, and clearing anything that does not need to be on the roof. Stone ballast and pavers also need to meet uplift requirements in high-wind areas.
Ask About the Whole Assembly When Replacing
If the roof is due for replacement, ask for the tested uplift rating of the complete system, from deck attachment to membrane. IBHS favors low-slope roof covers with recognized approvals, such as FM Approved, UL, or ICC-ES listings, because tested products come with known performance.
Choosing Hail-Resistant Roof Assemblies
In commercial roofing, hail resistance belongs to the whole assembly, not only the top layer. FM Approvals Standard 4470 tests the roof cover, insulation, and deck together, and its minimum hail level is Moderate Hail (MH). For hail-prone areas, IBHS recommends low-slope roofs that carry an FM 4470 Class 1-SH (Severe Hail) rating or a UL 2218 Class 4 rating.
The table below explains what the most common ratings mean.
| Rating | How It Is Tested | What It Tells You |
| FM Moderate Hail (MH) | A 2-inch steel ball weighing 1.19 pounds is dropped 81 inches onto the roof assembly. | The baseline hail level within FM 4470 approval. |
| FM Severe Hail (SH) | The same steel ball is dropped 141.5 inches, an impact of about 14 foot-pounds. | The level IBHS recommends for low-slope roofs in hail-prone areas. |
| FM Very Severe Hail (VSH) | 2-inch ice balls are fired from a launcher at a roof cover that has been heat-aged an extra 1,000 hours. | A tougher rating added in 2018 in response to more claims from hail larger than 2 inches. |
| UL 2218 Class 4 | The product is struck twice in the same spot by 2-inch steel balls and must stay functional. | Common for flexible products and metal panels. |
| FM 4473 Class 4 | The product is struck twice in the same spot by 2-inch ice balls and must stay functional. | Used for rigid coverings like tile and slate. |
Ratings are only part of the picture. A few other choices make a real difference:
- Cover boards. IBHS recommends a cover board in new roof systems to raise puncture resistance, and testing shows it helps hail performance as well.
- Hail guards on equipment. IBHS recommends guards for condenser coil fins, air intakes, fans, and other parts that could stop working if struck.
- Rated skylights. IBHS suggests skylights that meet a recognized impact standard, such as an FM Approval with a Severe Hail rating.
The right level for your building depends on its use and what your insurer expects. Ask your insurer whether it requires or rewards a specific hail rating before you choose materials.
What to Do in the First Days After a Storm
The first few days after a storm shape both the repair and the insurance claim. The Ohio Department of Insurance recommends documenting damage before cleanup, making safe temporary repairs, and keeping records of every step. Here is how that plays out for a commercial building:
- Keep people safe. Keep staff and tenants off a damaged roof, and watch for downed power lines, hanging debris, and wet floors near leaks.
- Document before you clean up. Take dated photos and video of the roof from a safe spot, along with ceiling stains, wet insulation, damaged equipment, and debris on the ground.
- Check the inside. Walk the top floor and look for drips, stains, sagging ceiling tiles, and rooftop equipment that tripped or stopped running.
- Make safe temporary repairs. Tarping or patching can limit further water damage. The Ohio Department of Insurance notes that insurers typically reimburse these costs as part of the claim, so keep every receipt.
- Contact your insurer promptly. Report the damage, ask about your deductible and claim timeline, and keep copies of all letters and emails.
- Get a professional assessment. Reputable commercial roofing services will start at the windward edges and corners, look beneath the membrane where hail or water may have done hidden damage, and give you written findings with photos.
Some storm damage is easy to miss from the ground. The table below lists signs worth reporting and what they may point to.
Frequently Asked Questions
Our roof came through the last big storm. Is it ready for the next one?
Not necessarily. FM Global notes that the wind at a specific building may have been weaker than the storm’s peak, and roofs with design or maintenance gaps can fail at lower speeds. A post-storm check can catch edges that loosened without failing.
Can hail damage a membrane roof without leaving visible holes?
Yes. Testing summarized by IIBEC found hail damage in the layer under the membrane even when the surface looked intact. Moisture testing or small sample cuts may be needed to confirm it.
Does a roof warranty cover wind or hail damage?
It depends on the terms. IBHS points out that standard warranties often limit coverage to certain wind speeds or exclude some weather events, and separate wind warranties are sometimes available.
Plan Your Roof’s Storm Season With CR3 American Exteriors
Storm prep is far easier to plan in calm weather than to rush after a warning. CR3 American Exteriors works on both residential and commercial exteriors, so we look at the roof edge, the walls, and the details where they meet. Our inspections are thorough, and our recommendations are straightforward, whether your building needs a few sections of edge metal re-secured or a replacement plan built around rated assemblies.
If a storm has already done its damage, we can help with the insurance claim for qualifying storm damage, and financing is available for qualified projects. Call CR3 American Exteriors, and talk through your building’s storm risks and the next steps that fit it.
