Commercial metal roofing
Structural metal: roof and structure in one
Panels engineered to span open purlins without decking, carrying load, resisting uplift, and closing the building in a single system. The backbone approach for pre-engineered and industrial structures.
When the panel is the structure
Most roofing sits on top of a structure; structural metal is part of one. These panels span from purlin to purlin with no deck beneath them, carrying live loads and wind uplift as working members of the building, which is why every meaningful number on this page traces back to load tables and tested assemblies rather than habit.
Structural metal isn't a single product. It's an engineered category spanning three families: structural standing seam with mechanically closed seams, heavy-rib exposed-fastener panels, and engineered systems designed over purlins and bar joists.
What makes a panel “structural” in the first place
A structural panel is one whose tested assembly qualifies it to span open supports and carry the roof's design loads without a continuous deck underneath. Rib geometry provides stiffness, gauge provides material strength, and the attachment transfers loads into the frame, all three verified together in the assembly's testing. An architectural pan over a plywood deck is an excellent roof, but the deck is doing the structural work, and the same panel over open purlin bays is a failure. The category boundary is whether the panel's own documents authorize the span.
Two structural families, compared
The practical choice usually comes down to structural standing seam versus heavy-gauge exposed-fastener panels: the first buys concealed attachment and very low slope capability, the second simplicity and economy.
| Attribute | Structural standing seam | Structural exposed-fastener |
|---|---|---|
| Common gauges | 24 ga common; 22 ga for higher loads or wider supports | Commonly 24 or 22 ga; some systems in 26 ga |
| Profile | ~3-inch trapezoidal rib; 18- or 24-inch coverage | Heavy ribs ~1.5 in on some systems; coverage ~28.8–36 in by profile |
| Attachment | Concealed clips at each support; mechanically closed seams | Through-fastened at every support with a wind-uplift-engineered pattern |
| Low-slope capability | Some mechanically seamed systems approved near ~1/4:12 | Commonly around ~1:12 with lap sealant, per the assembly |
| Maintenance profile | No field screws; flashings and terminations get the attention | Exposed gasketed fasteners require periodic inspection |
| Where it wins | Very shallow roofs, long runs, minimizing exposed fasteners | Budget-led projects, straightforward buildings, profile matching |
Representative structural system parameters
Orientation numbers for the category. The specific product's load tables and the project engineering are the only figures that count.
| Parameter | Representative range |
|---|---|
| Support condition | Open purlins or bar joists: no continuous deck |
| Purlin spacing | ~4–5 ft common in pre-engineered buildings; wider only where load tables and project engineering support it |
| Steel gauges | 24 ga common across the category; 22 ga for higher loads; some exposed-fastener systems in 26 ga |
| Seams and laps | Mechanically closed seams on standing seam systems; sealed, through-fastened laps on exposed-fastener systems |
| Slope range | From ~1/4:12 on certain mechanically seamed trapezoidal systems to ~1:12 and up for exposed-fastener assemblies with lap sealant |
| Attachment | At every support line, with denser patterns in corner and perimeter wind zones |
Span, purlin spacing, and the load-table discipline
How far can the panel go between purlins? Never a simple answer: capability moves with gauge, profile depth, wind and live loads, whether a bay is at the panel's end or middle, and the specific tested assembly. The 4-to-5-foot purlin spacing common in PEMBs exists because it suits common panel assemblies; going wider is possible only where load tables and project engineering say so. At reroof time, an existing building's purlin spacing is a fixed fact the new system must be qualified for.
The load path: panel to purlin to frame
A structural roof works as a chain: loads enter the panel, pass through clips or fasteners into the purlins, and travel down into the main frames. Gauge, profile, seam type, clip or fastener choice, attachment pattern, and purlin spacing operate as one tested assembly, swapping any single element without requalifying the chain breaks it.
Wind doesn't load that chain evenly, either: corner and edge zones see substantially higher uplift than the field, which is why attachment density commonly increases there, a spec that treats the whole roof as “the field” is underbuilt at exactly the points storms attack first. When we detail a structural roof, zone-by-zone attachment is in the drawings.
Retrofit over the top vs. panel-for-panel replacement
An aging structural roof has two main futures. Panel-for-panel replacement installs new panels qualified for the same purlin spacing, the cleaner path when the structure is sound and the building can tolerate open-roof phases. Retrofit systems instead build a new roof above the existing one on engineered sub-framing, keeping the building dried-in throughout and creating a cavity that takes new insulation economically, provided the frame is verified for the added load.
Occupancy, schedule, insulation goals, and structural findings decide between the paths; when a building qualifies for both, we present both.
Our approach
How structural metal projects run
Structural review
Purlin condition, spans, and load requirements establish the engineering envelope.
System engineering
Panel profile, gauge, and attachment schedule specified to the calculated loads.
Sequenced installation
Panels placed and secured in structural sequence. The building stays sound at every stage.
Uplift-critical detailing
Edges, ridges, and terminations detailed for the wind zones that fail first in storms.
Factors that drive structural metal project pricing
System family
Structural standing seam and heavy-rib exposed-fastener panels sit at different price points with different maintenance futures.
Gauge and profile
22 gauge over 24, and deeper ribs, add material cost that spans, loads, and exposure may require.
Measured spans and load requirements
Purlin spacing and design loads set which assemblies qualify, and qualifying assemblies set the material budget.
Wind-zone attachment engineering
Corner and perimeter uplift zones demand denser clips or fasteners than the field, multiplying hardware and labor.
Replacement path and frame condition
Panel-for-panel swap and over-the-top retrofit carry very different costs, and purlin remediation is priced from inspection findings.
Building operations during work
Keeping a plant or warehouse running under an open-roof sequence takes phasing, protection, and coordination: all real labor.
FAQ
Structural Metal Roofing questions, answered
What buildings use structural metal roofing?
Can an old structural metal roof be replaced without rebuilding?
How does structural metal handle hurricane winds?
Structural standing seam or exposed-fastener, which should we pick?
Can purlin spacing be widened when we reroof?
Industries we serve
Built for your kind of building
Every facility type has its own schedule, budget, and roof. We roof them all across South Mississippi.
Service area
Where we provide structural metal roofing
Based in Hattiesburg and serving Mississippi within about two hours, from the Pine Belt to the Gulf Coast.
- Purvis
- Sumrall
- Seminary
- Collins
- Ellisville
- Richton
- Waynesboro
- Columbia
- Poplarville
- Wiggins
- Lucedale
- Kiln
- McHenry
- Saucier
- Diamondhead
- Bay St. Louis
- Pass Christian
- Long Beach
- D'Iberville
- Ocean Springs
- Moss Point
- Pascagoula
- Crystal Springs
- Jackson
- Meridian
Don't see your town? If you're within about two hours of Hattiesburg, we most likely serve you.
Let's talk about your roof
A consultation, not a sales pitch: we assess your building, your operations, and your budget cycle, then propose the system that actually fits.