Design, Codes & Engineering

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Hello, and welcome. This is Super Structures General Contractors — a national general contractor headquartered in Powhatan, Virginia — here to help you and your clients build something that lasts. We're glad you're with us, and we look forward to connecting with you.

Alright, Design, Codes & Engineering. Don't let the plain title fool you. Here's the part that actually matters on the job: A PEMB is only as good as its design criteria — nail the loads (especially the easily-missed collateral load), the code edition, and the manufacturer-versus-EOR foundation responsibility split, because the system is engineered exactly to what you specify. Learn it well and you'll avoid the single most expensive category of metal building mistakes: the ones baked in before the steel is cut.

A PEMB is only "pre-engineered" once it knows what it must resist. The manufacturer's software will produce a stamped, code-compliant building for whatever inputs it receives — so getting the design criteria right up front is the single most important step on the job.

The loads the building must carry

• Dead load — the weight of the structure, panels, and insulation. The manufacturer calculates this.
• Roof live load — a minimum code load for maintenance and construction, commonly 20 pounds per square foot before reductions.
• Collateral load — everything that hangs from the structure after the building is done: sprinklers, ductwork, lights, ceilings, conduit, and cable trays. This is the load that is easiest to under-specify and the one that bites owners later. Sprinklered buildings commonly need a collateral allowance of several pounds per square foot; heavier mechanical systems need more.
• Snow load — from the ground snow load at the site, adjusted for exposure, thermal condition, and roof shape, with drift at parapets, steps, and adjacent buildings.
• Wind load — from the basic wind speed, exposure category, and the building's enclosure classification. Open or partially enclosed buildings see much higher internal pressures.
• Seismic load — from the site's mapped values and soil class, which also sets detailing requirements.
• Crane loads — bridge or monorail cranes add vertical, lateral, and longitudinal loads, plus fatigue and deflection considerations.
• Special loads — mezzanines, rooftop units, solar arrays, future expansion.

Codes and standards that govern

• The building must meet the locally adopted International Building Code (IBC) edition. The IBC references ASCE 7 for loads, AISC 360 for structural steel, and AISI S100 for the cold-formed purlins and girts.
• MBMA publishes the Metal Building Systems Manual, which defines common practice, serviceability recommendations, and the usual division of responsibility.
• The energy code (IECC or ASHRAE 90.1, as adopted) governs the roof and wall insulation assembly.
• Risk category (from the building's occupancy) scales the snow, wind, and seismic loads. A storage building and a fire station on the same site get different loads.
• Code editions and amendments vary by jurisdiction; always write the governing edition into the order.

Who stamps what

• The manufacturer's engineer designs and stamps the metal building system — frames, secondary, bracing, panels, and their connections — and produces a letter of certification listing the design loads and code.
• The project's engineer of record (EOR) confirms the design criteria, coordinates overall code compliance, designs the foundation, and handles anything not supplied by the manufacturer: mezzanines, canopies in conventional steel, masonry veneer support, and the like.
• The building official reviews both and inspects the work.

The foundation interface

The manufacturer provides column reactions and an anchor-bolt plan; the local engineer designs the foundation for those reactions and the site's soil. Rigid frames push outward at the base under gravity load — the horizontal thrust — so footings often need hairpins into the slab or tie rods between column lines. The manufacturer typically supplies anchor-bolt diameter and pattern but not embedment or the concrete design; that is the EOR's. This handoff is critical — a mismatch between the anchor-bolt plan the foundation was built to and the one the steel was fabricated to is one of the most expensive field problems in the business.

Going Deeper (Intermediate)

Collateral load is the classic trap. If the owner later hangs a sprinkler system, a suspended ceiling, or heavy mechanicals the building was not designed for, the purlins and frames can be overloaded, and retrofitting means reinforcement or added framing. Specify collateral load generously up front, and write it on the drawings so the next tenant's engineer can find it.

Serviceability matters as much as strength. Deflection and drift limits protect overhead doors, masonry veneer, and interior finishes. A frame that is strong enough but too flexible will crack brick, bind doors, and oil-can panels. MBMA publishes recommended limits; the EOR should state them in the specification rather than leave them to the manufacturer's defaults.

Because a PEMB is design-build, the manufacturer is responsible for the building to the loads you give them — garbage in, garbage out. Review the design criteria sheet on the approval drawings line by line against the specification before signing.

Advanced / Pro-Level

A frequent source of RFIs and disputes is the responsibility split between the manufacturer's engineer (the steel system) and the EOR (foundation and overall compliance) — define it in the specification, including who designs the framed openings, the mezzanine, and any conventional steel. Crane buildings add fatigue checks, runway beams, tighter deflection limits, and bracing for crane lateral loads; the crane's data sheet must be in hand at design time.

Watch temperature and expansion on long buildings, snow drift against taller neighbors and at parapets, and wind uplift at the roof edges and corners, where pressures are highest and purlin spacing tightens. Special inspections under IBC Chapter 17 apply to field bolting and welding; shop work from an IAS AC472 accredited manufacturer is commonly accepted by the building official, but confirm locally. Plan ahead for mezzanines, future expansion, and rooftop equipment so the frames are sized once.

Practice Challenge

An owner orders a PEMB warehouse as an unsprinklered storage building, then a year later wants to hang a full fire-sprinkler system from the roof. Why could this be a problem, and what should have happened? (Answer: if the building was not designed for that collateral load, the purlins and frames may be overloaded — sprinklers are a significant hanging load that must be specified at design time, and retrofitting can require reinforcement or added hanging framing. The lesson is to specify collateral load generously up front and record it on the drawings.)

In Practice

A project manager who does this well sends the manufacturer a one-page criteria sheet — code edition, risk category, every load, deflection limits, collateral allowance, and future plans — and compares it to the approval drawings before signing. A project manager who skips it signs whatever comes back, finds out at plan review that the risk category was wrong, and eats a redesign and a schedule slip.

Common Mistakes to Avoid

• Leaving collateral load at the manufacturer's default on a building that will be sprinklered
• Ordering to the wrong code edition or risk category and finding out at plan review
• Assuming the manufacturer's engineer designed the foundation or the mezzanine
• Accepting default deflection limits on a building with masonry veneer or large overhead doors
• Signing approval drawings without reading the design criteria sheet line by line

Takeaway: A PEMB is only as good as its design criteria — nail the loads (especially the easily-missed collateral load), the code edition, and the manufacturer-versus-EOR foundation responsibility split, because the system is engineered exactly to what you specify.

Educational content — not legal, engineering, safety, or contractual advice. Metal building design must be performed by qualified engineers to the adopted codes and the manufacturer's specifications; code editions, OSHA rules, and local requirements vary by jurisdiction, so verify them for your specific project.