Pre-engineered metal building erection field guide

Metal building erection, and why the anchor bolts decide it

A pre-engineered metal building, a PEMB, is a steel building system the manufacturer engineers and fabricates as a complete kit and ships to the site for a crew to erect. The kit comes in four parts: the primary framing, the rigid frames of tapered columns and rafters; the secondary framing, the purlins and girts that carry the panels; the bracing that resists lateral load; and the metal wall and roof panels that close it in. The frames are cut, drilled, and welded in the shop to a number, so the field work is assembly, not fabrication.

The one thing that decides whether the building goes up is the anchor bolts. The frames are fabricated to land on bolts set to the manufacturer's anchor bolt setting plan, and the columns have no give in them. Set the bolts off location, off pattern, or at the wrong projection, and the base plates do not drop over the rods, the frame does not stand where it belongs, and the crew is stuck on day one with steel hanging on the crane.

The work in order is short to say and unforgiving to do. Set the anchor bolts exactly to the setting plan. Erect the frames in the sequence the manufacturer drew and keep them braced until the building is stable. Then sheet it and follow the erection drawings the whole way. This is the metal building system. For custom structural steel designed and built for one project, read the structural steel erection guide. For the standing seam roof that can go on top, read the standing seam guide.

Why do anchor bolts decide whether a metal building goes up?

Anchor bolts decide it because a rigid frame is fabricated to one set of holes and lands on the bolts cast in the concrete, with almost no tolerance to absorb an error. The base plate is punched at the shop to the column's bolt pattern. The foundation crew, working by others, casts the anchor rods to the manufacturer's setting plan. If those two do not match on erection day, the steel does not fit, and there is no clean field cut that fixes it.

Off-location bolts are the make-or-break failure on a metal building. A group set an inch off, rotated, spread, or short on projection, and the base plate will not seat, the column will not plumb, and the rafter at the peak misses its mate. Now the fix is somebody else's call: ream, a field plate, an epoxy anchor, or a chipped and recast pier, none of it done without the engineer of record and the manufacturer signing it.

This is why the bolts get measured against the setting plan before the pour and surveyed again before the first frame flies, not discovered when the column is on the hook. Set the bolts right and the rest of the building follows. Set them wrong and you are negotiating repairs before you have raised a single frame. Hedge any anchor-bolt repair or modification to the engineer of record and the manufacturer every time.

What is the difference between a PEMB and structural steel?

A pre-engineered metal building is a standardized steel system the manufacturer engineers, optimizes, and fabricates as a kit, so the crew erects it. Custom structural steel is designed for one specific project by the engineer of record, detailed and fabricated to that design, and erected as a one-off frame. The PEMB trades custom geometry for speed and cost: tapered built-up frames sized tight to the loads, light cold-formed secondary, and a panel skin, all shipped as a package with its own erection drawings.

That difference shows up in the field. On a PEMB the engineering is done and proven by the manufacturer, the members carry part marks that match the manufacturer's drawings, and the connections are mostly bolted clips rather than field-welded moment joints. On custom steel you are setting wide-flange columns, beams, and braces detailed by a steel fabricator, with snug-tight and slip-critical bolting and field welds inspected by a CWI. The stability problem is identical on both: a partly-built frame is unstable until braced and connected.

PEMBs own the warehouse, the commercial shell, the church, the hangar, the riding arena, the work where clear span and a fast dry-in beat a custom frame. The structural steel erection and connections guide covers the custom side, the OSHA Subpart R rules, and the bolting and welding in depth. Read it as the sibling to this one. The safety discipline carries straight across.

The kit: what ships and what each part does

A metal building shows up as a bundle of marked steel and a stack of panels, and it helps to see it as four systems that each do one job. The primary framing takes the load to the ground. The secondary framing carries the skin and braces the frames. The bracing resists the sideways loads. The panels close the building in and shed water.

Every part is cut to the manufacturer's design and tagged to a part mark on the erection drawings. There is no spare and no generic substitute. A purlin from the wrong line does not bolt to these clips, and a clip from one product line does not match another's frame.

The primary framing: rigid frames

The primary framing is the rigid frames, the main structure that carries roof, wind, and snow load down to the anchor bolts. A rigid frame is a built-up tapered column and rafter, welded deeper where the moment is highest and pinched where it is low, which is the shape that gives a PEMB its economy. The frame works as a moment frame: the rigid knee at the column-to-rafter joint resists the lateral load without a separate braced bay in that line.

The big decision is clear span versus modular. A clear-span frame runs column to column with nothing in between, which is what a warehouse, an arena, or an aircraft hangar needs, and the frame gets deep and heavy to do it. A modular, or multi-span, frame drops interior columns at intervals, which lets the rafters and frames run lighter and cheaper for a wide building where interior columns are acceptable. The manufacturer engineers the frame to the span, the loads, and the building code for the site.

Frames go up in pieces and bolt together at the field splices, knee and peak, on the ground or in the air depending on the size and the crane. The columns land on their base plates over the anchor bolts. The geometry is the manufacturer's, fixed at fabrication, so the field sets the frame the drawing draws and does not redesign it on the iron.

The secondary framing: purlins and girts

The secondary framing is the purlins and girts, the light members that span between the rigid frames to carry the panels and brace the main steel. Purlins run across the rafters and hold the roof panels. Girts run along the columns and hold the wall panels. Both are cold-formed Z or C sections, rolled from light-gauge steel rather than the built-up plate of the frames, and they bolt to the primary with clip angles.

The secondary does two jobs at once, and the second one gets forgotten. It carries the skin, moving wind and snow off the panels into the frames. It also braces the frames, because a purlin or girt bolted across the compression flange holds that flange from buckling sideways, working with the flange braces to keep the slender frame stable. Pull a line of purlins to chase a fit problem and you have taken bracing out of the frame, not just panel support.

Z purlins lap at the frames so the runs act continuous, which is part of how the manufacturer sized them, so the lap length and the bolts at the lap are not optional. The base angle, the eave strut, and the door framing are secondary too. Set them to the manufacturer's drawings, because the spacing was engineered to the panel and the loads, not picked for convenience.

The bracing: wind bracing and flange braces

The bracing is what keeps a metal building standing against the loads that try to push it sideways and fold it over, and the building cannot stand without it. Wind bracing, usually steel rod or cable run as an X in the wall and roof planes of designated braced bays, carries lateral wind and seismic load down to the foundation in the lines where the rigid frames alone do not. The braced bay is engineered into specific bays, not every bay, and the rods get tensioned to take up the slack.

Flange braces are the other half, and they are small and easy to leave out. A flange brace is a short angle that ties the inside flange of a rafter or column to a purlin or girt, holding that flange from buckling sideways under load. The frames are slender by design, so the inside flange depends on those braces and the secondary to stay straight under compression. Miss the flange braces, especially in the end bays where uplift puts the bottom flange in compression, and you have left out part of what holds the frame up.

The roof and wall diaphragm, the panels fastened to the secondary, adds stiffness once it is on, but it does not replace the engineered bracing. Where the bracing goes, how the rods are tensioned, and which bays are braced are the manufacturer's and the engineer's design, shown on the erection drawings. Install every brace the drawings call for, in the bays they call for, and tension the rods as specified. Do not omit a brace because the building looks solid without it. Hedge every bracing question to the manufacturer, MBMA and AISC, and the engineer of record.

How do you set anchor bolts for a metal building?

You set the anchor bolts exactly to the manufacturer's anchor bolt setting plan, the drawing that gives the location, the pattern, the projection, and the diameter for every column base. The setting plan is the most important sheet for the foundation crew, because the frames are fabricated to land on those bolts and nothing else. Location is where each group sits on the grid. Pattern is the spacing and orientation of the bolts within the group. Projection is how far the threaded end stands above the concrete so the leveling nut and the base plate have what they need.

The tolerances are tight, and they are not a suggestion. Manufacturers and AISC 303 hold anchor rods within fractions of an inch, commonly on the order of 1/8 in within a bolt group and a small fraction more between groups, so confirm the exact tolerance on the plan and in AISC 303 for the project. Measure the group, the spacing, the diagonal, and the elevation, twice, against the plan before the concrete goes in. The foundation is by others, so the erector and the concrete crew coordinate this before the pour, not after.

The bolts cannot be field-modified on a whim. OSHA and the manufacturer are clear that anchor rods are not repaired, bent back, or extended without the engineer of record's approval, the same rule that governs custom steel. Set them right the first time, because every error here is paid for at erection. Hedge the setting tolerance, any repair, and the projection to the manufacturer's setting plan, AISC 303, and the engineer.

The foundation under the building

The foundation, the concrete that carries the building and holds the anchor bolts, is by others on almost every metal building job. The manufacturer supplies the building, the reactions, and the anchor bolt setting plan. A separate foundation engineer designs the slab, the piers, the footings, and the grade beams to those reactions and the soil. The erector inherits whatever the concrete crew built, so the coordination between the two trades is where jobs are won or lost.

What the erector checks before the steel flies is short and worth the time. The concrete is poured, cured enough to take the load, and at the right elevation. The anchor bolts are located, projecting correctly, and surveyed against the setting plan. The piers are level across the building so the columns set plumb and the bases bear. A pier a half inch low or a bolt group off line is a foundation problem that becomes a steel problem the moment a frame lands on it.

The base plates set on leveling nuts or shims to elevation, with non-shrink grout packed under them later for full bearing where the detail calls for it. The reactions, the bolt design, and the bearing detail are the engineer's, so verify the foundation was built and surveyed to the drawings before the first frame goes up, and take any mismatch back to the engineer and the manufacturer.

Setting the bolts with a template

The way you hold the anchor bolts true through the pour is a template, a steel or plywood jig that fixes the bolts in the exact pattern, spacing, and projection of the setting plan while the concrete goes in around them. Loose bolts wired to rebar drift when the concrete is placed and vibrated, and a group that wandered an inch is the failure that stops erection cold. The template holds the pattern, keeps the bolts plumb and perpendicular to the bearing surface, and sets the projection so every base in a line matches.

Build or order the template to the plan, set it to the grid lines and the column elevation, and brace it so the placement crew cannot knock it out. Check the group against the plan before the pour, again, and recheck the projection and the spacing after the concrete is placed but while you can still adjust. This is the cheapest rework prevention on the whole job. Catching a bad group on the template costs minutes. Catching it when a frame will not seat costs days.

The tolerance, the bolt material, and the embedment are the engineer's and the manufacturer's, so set the template to the setting plan and hedge the numbers to those documents. The crew that owns the pour owns the template, and the erector who has to land steel on it should be there to confirm it before the truck shows up.

The erection sequence

The erection sequence is the order the building goes up, and on a metal building it is set to keep the frame stable at every stage, not to suit the crane. The pattern is consistent across manufacturers: erect the braced bay first to get a stable, plumb starting point, stand the rigid frames and brace them as they go, tie them together with the purlins and girts, plumb and square the steel, then sheet it. Sheeting goes on after the frame is plumbed and braced, never before.

Each step depends on the one before it. The braced bay gives the rest of the building something stable to build off. The frames go up bolted at the splices and held by temporary bracing and the secondary until the permanent bracing is in. The plumbing and squaring take the lean and the rack out before anything locks the geometry. The panels then close it in and add diaphragm stiffness, but they are the last structural step, not a substitute for the bracing under them.

The sequence is the manufacturer's, shown on the erection drawings, and changing it on the ground is how a building ends up with frames standing unbraced longer than the plan allowed. Follow the order. If the sequence has to change for a site conflict, it goes back to the manufacturer and the engineer, not around them.

Starting with the braced bay

The braced bay is the first thing you stand, because it is the stable reference the whole building hangs off. A braced bay is a bay with the wind bracing, the X of rods or cable, designed into it, so once its two frames are up, tied with the eave struts and purlins, and the rods are tensioned, that bay stands plumb and square on its own. Everything erected after it leans on that stability until its own bracing is in.

Get the first bay right and the rest of the building comes up straight off it. Get it racked or out of plumb and you have built the error into every bay that follows, because crews plumb and align the new steel to what is already standing. So the braced bay gets the most care: set both frames, brace them, tension the rods, and prove it plumb and square before the next frame goes up.

Which bays are braced is the manufacturer's design, marked on the erection drawings, and it is usually an end bay or near it. Do not start in a bay that has no bracing and expect to hold it, and do not skip tensioning the rods because the bay looks fine. The braced bay is only a reference if it is actually braced and actually plumb.

Keeping the frames braced until they are stable

This is the rule that kills people on metal buildings when it is broken. A rigid frame is unstable until it is braced, and the crane does not come off it until it is. A frame standing on its anchor bolts with the splice bolts in is still a tall, slender thing with nothing holding it sideways. Until temporary guy cables and the permanent bracing and secondary tie it to a stable bay, wind or the swing of the next pick can fold it over, and metal building frames are light enough to go down fast.

Temporary bracing is the erector's responsibility, engineered and installed, not improvised. Guy cables, temporary diagonal bracing, and the bolted purlins and girts hold each frame until the permanent X-bracing and flange braces take over. OSHA's metal building rule requires rigid frames to have 50 percent of their bolts, or the number the manufacturer specifies, whichever is greater, installed and tightened on both sides of the web at each flange before the hoisting equipment is released. That is the floor for letting go, not the finished frame.

Do not release the crane until the frame is braced and secured, and do not pull a temporary brace early to get it out of the way of the next pick. That removes the support the frame is leaning on before its replacement exists, which is the collapse mechanism, plain and direct. The same stability discipline governs custom steel, and the structural steel erection guide covers the unstable-frame hazard in depth. Hedge the bracing, the bolt count, and when supports come off to the manufacturer, OSHA Subpart R, and the engineer.

Plumbing and aligning the steel

Plumbing and aligning is pulling the frame true, columns plumb and bays square, before the sheeting locks the geometry in. A frame goes up with slack in every bolted joint and the tolerance of the connections, and left alone it leans and racks. The crew pulls it straight with the plumbing guys, turnbuckles, and come-alongs, working off a survey or at least string lines and a level, until the columns are plumb and the diagonals of the bays measure equal.

The order is the part that gets reversed by crews in a hurry. You plumb and square the frame first, then you sheet it, because the panels and their fasteners stiffen the building and fix whatever shape it is in. Sheet a racked frame and you have locked the rack in, and now the doors do not fit, the panels run out of square against the trim, and the fix is pulling sheets back off. Hold the plumbing guys until the bracing that keeps the frame true is in and tight.

The tolerances come from the manufacturer and AISC 303, with frame plumbness commonly held to a small fraction of the height between working points. Pull the steel to that, confirm it, then let the sheeting crew start. Plumb the building before you skin it, every time.

The connections: bolted, not welded

A metal building is a bolted system, which is one of the things that makes it fast. The frames connect at the field splices, knee and peak, with high-strength bolts through the fabricated end plates, and the secondary bolts to the primary with clip angles. There is little to no field welding on a standard PEMB, and that is by design: the shop did the welding on the built-up frames, and the field bolts it together to the manufacturer's drawings.

The bolts are high-strength structural bolts, and the manufacturer's drawings call out the size, the grade, and the number at each connection, along with how tight. The frame splices at the knee and peak carry the moment, so their bolts matter most. Bring the whole pattern up and tighten as the drawings and the bolt spec require. The OSHA rule on getting 50 percent of the frame bolts in and tightened on both sides of the web before releasing the crane is a stability minimum, not the finished connection.

What controls the bolting is the manufacturer's drawings and the bolt specification, the same RCSC framework that governs custom steel bolting. The structural steel guide covers snug-tight, pretensioned, and slip-critical joints and how they are verified. On a PEMB, install and tighten every connection to the manufacturer's drawings, and hedge the torque and tightening method to those drawings and the engineer.

The metal panels: wall and roof

The panels are the skin, the wall and roof sheets that close the building in and shed water, and they come in two families. Through-fastened, or screw-down, panels are screwed straight through the face into the purlins and girts, the fast and economical choice that owns most metal building roofs and walls. Standing seam roof panels ride on concealed clips with the seam locked up above the water line, the longer-life choice where the roof has to last and stay dry under harder weather.

Sheeting is more than hanging metal. The panels lap side to side and end to end, the laps and the eave, ridge, and rake get closures, foam or metal pieces cut to the panel profile and bedded in sealant, and the whole thing gets trimmed out at the corners, openings, and terminations. The roof usually carries insulation between the panel and the purlins. The panels also act as a diaphragm once fastened, adding stiffness to the braced frame, which is why the fastener pattern is engineered and not random.

The choice between screw-down and standing seam, the slope it can run, the fastener pattern, and the closures all come from the manufacturer's details for the exact panel. The standing seam metal roof guide covers the seam types, the floating clips, the thermal movement, and the slope limits in depth. Read it for the roof. On a metal building, follow the manufacturer's panel details and do not carry numbers between product lines.

Panel fasteners and where the roof leaks

The number one leak on a screw-down metal building is the fastener, so the screws are where the dry-in is won or lost. A through-fastened panel is held by a self-drilling screw with a bonded washer, and that washer is the only seal at every hole. Drive it square and to the right depth so the washer compresses and seats flat. Over-drive it and you crush the washer and dimple the panel into a puddle. Under-drive it and the washer never seals. Drive it cocked and water runs under the edge. Hundreds of screws on a roof, and every one is a potential hole.

The laps and the closures are the other leak path. Side and end laps get the sealant tape the manufacturer specifies, run continuous, because a skip in the bead is a planned leak. The closures at the eave, ridge, and rake fill the ribbed gap under the trim and keep weather and pests out, bedded in sealant, not left open. The screws into the laps and at the closures hold the system tight against uplift and water both.

Screws back out over the years as the metal expands and contracts, which is the long-term failure on a screw-down roof and the reason standing seam exists. Use the fasteners and sealant the manufacturer specifies, drive them right, and keep them out of the flat where they would sit in the water path. Keeping the building dry is mostly keeping the fasteners and closures right.

Metal building insulation

Metal building insulation is usually a faced fiberglass blanket rolled out over the purlins and girts and trapped between the secondary and the panels as the sheeting goes on. The facing is the vapor retarder and the finished interior surface, so it has to stay clean and unbroken, and the blanket is banded or supported so it does not sag between purlins and choke the cavity.

The detail that matters thermally is the thermal break. A blanket crushed hard at every purlin loses much of its value at those lines, so banded systems, thermal blocks, or a layered approach hold the insulation off the metal-to-metal contact and cut the heat path through the framing. The R-value, the facing, and the system are the manufacturer's and the energy code's call for the building and the climate, so install it to those details and confirm the assembly meets the adopted energy code.

Framed openings and field cuts

Openings, the doors, overhead doors, and windows, are framed into the secondary with their own jambs, headers, and trim, and most of it ships as part of the kit cut to the opening. Overhead doors get a header and jamb framing sized for the door and the wind load, and the door's own hardware ties into it. Walk doors and windows get formed framing and trim that the panels and closures detail into.

Field cuts happen, but they are where rust and leaks start if they are sloppy. Cut a panel for an opening or a penetration and the cut edge has lost its coating, so it gets sealed and trimmed, and the swarf, the hot metal filings from the cut, gets swept off the panel before it bakes in and rusts a thousand little spots. Flash and trim every opening to shed water, lap the upslope side, and keep fasteners out of the water path the same as anywhere else on the skin.

The crane and the picks

Every frame, and most of the heavy steel, goes up on a crane, and the pick is governed by the load chart, the rigging, and a pick plan, not the operator's read of the day. The weight of the frame or column, the radius it has to reach, and the crane's configuration decide whether the pick is inside the chart, and a piece that is fine close in can be over capacity swung out to the far corner of the building. Metal building frames are light compared to custom steel, but a long rafter is awkward and wants to bend and swing.

Rig the member at its picking points so it flies the way it has to land, with rated slings and shackles and a tag line to control it from the ground. Big frames often get assembled on the ground, knee and peak bolted up, then picked as a unit, which means rigging a long, limber piece that can buckle if it is picked at the wrong points, so follow the manufacturer's or the engineer's rigging guidance for the lift.

The crane and rigging discipline has its own standard, OSHA Subpart CC, and the full treatment of the load chart, the power-line clearance, sling angles, and the exclusion zone lives in the crane and rigging work. On a metal building the crane and the steel are one operation, so plan the picks and keep people out from under the load.

Safety: the unstable frame, the fall, the crane, and the wind

The safety picture on a metal building is the steel erection picture, and OSHA regulates it under 1926 Subpart R, with a section written specifically for systems-engineered metal buildings at 1926.758. The metal building rules cover the four-anchor-rod minimum for columns, the 50-percent-of-frame-bolts requirement before releasing the crane, and limits on using purlins and girts as a walking surface or a fall-arrest anchorage. The compliance officer opens Subpart R on this job. The field works to it and to the site-specific erection plan.

The hazards rank the way they do on any steel job. The unstable partly-built frame is first, and it is answered by bracing and sequence. Falls are next, and the steel-erection trigger and the connector and decking provisions apply, with the perimeter cable and fall arrest going up as the building goes up. The crane and struck-by exposure means nobody works under a suspended load. Wind is the metal building's own sharp edge: an unbraced frame, light and broad, is a sail, and a panel being carried up is worse, so the pick stops and the frame waits at the wind limit the manufacturer's and crane's charts set.

None of this is field-judgment territory. The structural steel erection guide covers Subpart R, the fall-protection triggers, and the unstable-frame hazard in depth, and it reads straight across to metal buildings. Hedge the stability, the bracing, the bolt counts, and the fall protection to OSHA Subpart R, the manufacturer, MBMA, and the engineer of record, and confirm the current standard and any stricter state plan before acting on a number.

The erection drawings and the part-mark system

The erection drawings are the manufacturer's set that tells the crew how the building goes together, and they are the law on a PEMB the way the shop drawings are on custom steel. They carry the frame lines and the grid, the anchor bolt setting plan, the part marks for every member, the bracing layout, the connection details, the panel and trim layout, and the erection sequence. Read them first and keep them on site. The building was engineered to them, and the field's job is to assemble what they draw.

Every member is tagged with a part mark that matches the drawings, so the crew can sort the steel and find the right piece in the right place at the right time. A frame line, a purlin, a brace, and a clip all carry a mark, and a piece flown up and found wrong at the connection is a wasted pick and a stalled crew. Lay the steel out by mark and sequence on the ground, the same shake-out discipline as any steel job.

When the steel does not match the drawings, a part is short, a hole is off, a brace is missing, the answer is to stop and go to the manufacturer and the engineer, not to fabricate a fix on the iron. The drawings are the record of how the building was engineered to stand. Follow them, and route any deviation back through the people who drew them.

What to document

The erection record proves the building went up the way it was engineered, and it is what answers the question later when an inspector, the manufacturer's warranty, or the next contractor opens something up. The pieces that matter are the anchor-bolt survey against the setting plan, the sequence and bracing that were followed, the connection bolting, the panel and closure work, and the as-built showing the frame plumb and square. Capturing these as the work happens, on a field tool like FieldOS, keeps the record tied to the bay and the day instead of reconstructed at closeout.

Common mistakes

• Setting the anchor bolts off the manufacturer's setting plan, so the frames do not land and the job stalls on day one.
• Releasing the crane before the frame is braced and the required bolts are in and tightened.
• Leaving out bracing, wind X-bracing or flange braces, or skipping the rod tensioning.
• Panel fastener leaks from screws driven crooked, over-driven, or under-driven, or from missing closures and sealant.
• Sheeting the building before the frame is plumbed and squared, locking the rack in.
• Running the wrong erection sequence instead of starting from the braced bay the drawings call for.
• Repairing, bending, or extending an anchor bolt without the engineer of record's and the manufacturer's approval.
• Substituting parts between manufacturers, or carrying panel and clip numbers from another product line.

Field checklist

Standards and references

OSHA 1926 Subpart R is the steel erection standard, and the systems-engineered metal building section at 1926.758 covers the metal building specifics: the four-anchor-rod minimum per column, the requirement that rigid frames have 50 percent of their bolts or the manufacturer's number, whichever is greater, installed and tightened on both sides of the web at each flange before the hoisting equipment is released, and the limits on using purlins and girts for walking or fall-arrest anchorage. Fall protection follows the steel-erection provisions at 1926.760. Crane work on the same site falls under Subpart CC.

The building system itself comes from the metal building manufacturer and is governed by MBMA, the Metal Building Manufacturers Association, whose Common Industry Practices set the responsibilities of the manufacturer, the contractor, the erector, the owner, and the engineer of record. The structural design and bolting reference AISC, the American Institute of Steel Construction, with AISC 303, the Code of Standard Practice, setting erection tolerances and anchor-rod placement, and the cold-formed secondary following the AISI specification. The foundation and the building reactions are the engineer's, and the anchor bolt setting plan is the manufacturer's.

Three things hold above the citations. Set the anchor bolts exactly to the manufacturer's setting plan, because the frames land on nothing else. Erect in the sequence and keep the frames braced until the building is stable, never releasing the crane or pulling a brace early. Fasten the panels right and follow the manufacturer's erection drawings the whole way. The section numbers and the exact requirements shift between editions and interpretations, and a state plan can be stricter, so confirm the current standard, the manufacturer's drawings, MBMA and AISC, and the engineer of record before acting on any one of them.

Units, terms, and conversions

A metal building carries its own vocabulary, and the same idea reads differently across the order documents, the erection drawings, and the OSHA standard. The terms below are the ones a crew and an inspector use on a metal building job.

Pre-engineered metal building (PEMB)

A steel building system the manufacturer engineers and fabricates as a kit of rigid frames, secondary, bracing, and panels, shipped to the site to erect

Rigid frame / primary framing

The built-up tapered columns and rafters that form the main moment-resisting structure and carry the load to the anchor bolts

Purlin / girt (secondary)

Cold-formed Z or C members that span between frames to carry the roof (purlins) and wall (girts) panels and brace the frames

Wind bracing / flange brace

Rod or cable X-bracing that resists lateral load in braced bays, and the short angle that holds a frame flange from buckling

Anchor bolt setting plan

The manufacturer's drawing giving the location, pattern, projection, and diameter of every anchor bolt the frames land on

Braced bay

A bay with wind bracing designed into it, erected first as the stable, plumb reference for the rest of the building

Through-fastened vs standing seam

Screw-down panels fastened through the face into the secondary, versus concealed-clip panels with the seam locked above the water line

Erection drawings

The manufacturer's set with frame lines, part marks, bracing, connections, panel layout, and the erection sequence

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