A rating means nothing without its criteria
“Rated for 140 mph” is not a fact about a building. It is a fact about a building at a wind speed, an exposure, a risk category and an enclosure — change any one and the same steel passes or fails. This is what to nail down, and how to take apart anybody’s claim including ours.
Nine lines, before any number means anything
Every sealed set opens with this and every honest quote is built on it. Get one wrong and the rest of the package is decoration.
// Wind and snow come off the ASCE 7 Hazard Tool at your actual latitude and longitude — never off a “typical speed by city” table. A site twenty miles inland can differ by 15 mph, and the plan reviewer is checking the exact coordinates, not the town name.
How your wall sheeting changes the design case
A carport with one wall sheeted is not automatically “open”. Free-roof pressure coefficients on a structure with enough sheeting to pressurise is the single most common mistake in this industry. Pick what you are actually building.
Open chart
A genuine open building. Free-roof net pressure coefficients apply, and the roof is designed for uplift acting on both faces rather than for a pressure difference across an envelope.
Open chart
Both end walls fully open and the side walls sheeted only three feet up. Still takes the open chart — three feet is not enough to pressurise the inside.
Open chart, spacing reduced 6"
Both ends open, side walls sheeted more than three feet. Start from the open chart and then tighten the frame spacing by six inches — the sheeting catches enough wind to matter.
This is the case people get wrong. It looks like a carport and it is not designed like one.
Enclosed chart
Everything sheeted except one end wall. It takes the enclosed chart, and the frame at the open end needs either a gabled end or doubled welded legs and roof to carry what the missing wall was carrying.
The open-end frame is a different frame. A set that shows one typical frame throughout has not addressed this.
Enclosed chart
An ordinary enclosed building. Internal pressure applies, and the maximum length under a single sealed set is commonly fifty feet before a doubled centre frame is needed to break it up.
Who actually has authority over your build
Most people get this wrong in both directions — assuming a permit is needed when nobody can require one, or assuming none is needed inside a city that plainly requires one.
Not an agricultural exemption — no one has jurisdiction to require a structural permit. County power in Texas is narrow and statutory: floodplain, septic, subdivision platting, manufactured housing, TDI windstorm in the fourteen coastal counties, and fire code in certain populous counties. General building codes are not on that list.
Cities are different. Local Government Code §214.212 and §214.216 set a floor at the IBC/IRC as they existed May 1, 2012, and the larger cities have adopted well past it — Fort Worth is on 2021 IBC, which references ASCE 7-16.
“No permit required” is not “no engineering required.” A structure that fails still fails, and the liability does not disappear with the permit requirement. We design to the code either way.
How to take apart a rating claim
Ranked by what actually kills a design. If somebody hands you a spec sheet, these are the five questions in the order worth asking them.
Rated for 90 mph Exposure B, site is 115 mph Exposure C. The sheet is not wrong — it is about a different building on a different site. Check the rating’s exposure and risk category, not just its wind speed.
Free-roof coefficients used on a structure with sheeted walls. See S2.0 — this is the one that gets rejected most.
“Anchor per manufacturer” with no evaluation report, no calc, no uplift number. On a light open structure the anchor is the whole ballgame — 0.6D + 0.6W is what governs it, and post-installed anchors need a current ICC-ES report cited on the submittal.
Clear wind flow only and no obstructed case; Load Case A and no Case B. If you are going to park equipment or stack hay under it, obstructed is the honest case and its suction is worse.
The member passes strength and fails serviceability. Formed metal has its own limits — panel L/60 total, purlins L/150 live, girts L/90 wind.
What we hand you, and who seals it
Worth being precise, because this is where customers get surprised at the counter of a building department.
What comes with the building
- The design criteria your building was built to, written down
- Member schedule, frame and purlin spacing for your loads
- Anchor layout and the uplift it was checked against
- Shop welds only — field connections are screwed, so no special inspection trips
What a seal is, and is not
A structure that needs a permit needs a licensed Texas PE to review the package, take responsibility for it and seal it. A seal is also fenced: it covers the steel we designed and supplied. It does not cover your slab, your soil, your zoning, or the attachment to an existing building.
Certifications also expire. Ask any supplier — us included — for the seal date and the stamp expiry before you submit anything. An expired set cannot be filed.
The rollformers, decoilers and benders in Azle came from ELM Manufacturing Systems, our sister company, which designs and builds metal-forming machinery — and sells it to other manufacturers. The machines and the buildings share engineers.
Tell us the two coordinates and what is going inside, and we will price it against the criteria above rather than against a chart.