Steel vs post-frame vs wood: how to frame a barndominium

Most barndominiums are framed in one of three ways: a steel rigid frame (a metal building home), large wood posts on a wide grid (a post-frame or pole barn house), or ordinary wood studs and trusses (stick framing). Steel is built for the widest column-free spans, post-frame is the wood cousin of the metal building, and stick framing is conventional light-frame construction, which the residential code's prescriptive tables cover. Choose by span, foundation, wall build-up and what your building department, lender and insurer accept, not by the siding, because all three can wear metal, wood or stone.

A note on our plans. Every BarndoVista plan set is drawn for conventional wood (stick) framing. A steel or post-frame version is an adaptation your builder or engineer makes, and structural sizing is not part of the set, which is unstamped. Codes, loads and permit rules also differ by state, county and city, so your local building department and a licensed engineer decide everything structural below. See what a plan set includes.

The three systems in plain words

Steel rigid frame (metal building home)

A metal building home is a house inside a steel rigid-frame shell, which the metal building industry calls a metal building system. Welded steel columns and rafters, often tapered, form frames that sit about 25 ft apart. Roll-formed steel purlins on the roof and girts on the walls span between the frames and carry the roof and wall panels. One maker's specification says rigid frames are commonly used for spans from 40 ft to over 150 ft, and tapered-beam frames for buildings 20 to 60 ft wide, so the roof of a house needs no interior columns.

Two terms need translating. "Red iron" is about the paint: the specification says framing that is not galvanized gets one shop coat of red primer, so red iron names the primer coat, not a kind of building. "Pre-engineered" is the other. A speaker from the Metal Building Manufacturers Association told a U.S. Department of Energy (DOE) webinar that the word is a misnomer, because these buildings are custom designed by engineers rather than picked out of a catalog.

"Steel frame" can also mean a steel-stud building, which uses cold-formed steel studs in place of wood studs. The same webinar separates steel-stud buildings from metal buildings, and this guide means the rigid-frame kind. A steel frame does not force a look, either: the speaker noted that metal building systems nearly always have a metal roof but do not always have metal walls.

Post-frame (pole barn house)

Post-frame is the industry's name for what many people call a pole barn. The National Frame Building Association (NFBA) reproduces the industry's standard definition in its design manual. It describes primary frames of wood posts used as columns, with roof trusses or rafters attached to the posts directly or through girders. Purlins in the roof and girts in the walls tie the frames together. Posts can be embedded in the ground on footings, or attached to piers, walls or a slab. Steel brackets on concrete piers let post-frame homes be built on any type of foundation, including crawl spaces and basements, according to Montana's Department of Environmental Quality (DEQ), which adds that slabs seem to be the most common choice. A pole building is the case where every post is a round pole. NFBA calls the system analogous to a low-rise metal building, with wood members in place of steel.

Post spacing is far wider than stud spacing. NFBA says posts sit at least 4 ft apart, and where trusses bear directly on them the spacing is usually at least 6 ft, often 8 ft and sometimes 10 to 12 ft. Minnesota's Department of Labor and Industry (DLI) says post-frame often needs a post and footing every 6 to 8 ft, in place of the continuous perimeter footing of a stick-built home. The wall sections between posts carry no roof load, so doors and windows fit most easily between posts.

Stick framing (wood studs and trusses)

Stick framing builds walls from wood studs, usually 16 or 24 in apart, under roof trusses or rafters. It is conventional light-frame construction, the kind of building the residential code covers with prescriptive tables. Minnesota DLI notes that the state's residential code, built on the 2018 International Residential Code (IRC), gives prescriptive requirements for conventional light-frame construction and none for post-frame. Parts of a stick-framed house can still need an engineer when they go past the code's limits.

Hybrids

Many barndominiums mix systems. In a February 2024 survey by the National Association of Home Builders (NAHB), 30% of the builders who build barndominiums described theirs as a mix of traditional residential and post-frame construction. Separately, 26% described theirs as post-frame homes with metal siding (builders could give more than one answer). A plan that puts a house and a shop under one roof, like the Prairie Works, is a natural place to ask a builder about a hybrid. Whatever mix you choose, the wall between the two parts needs its own design.

Steel vs post-frame vs wood, side by side

Each cell names its source. Use the table to prepare questions for your builder and engineer, not to pick a design.

Whatever the frame, a barndominium is a new home. NAHB notes that in the typical jurisdiction it needs a residential building permit. Local zoning can add limits of its own, and Minnesota DLI points out that zoning may restrict metal exterior finishes, so check that too.

When each system tends to fit

• Steel tends to fit when you want one very wide open space, such as a large shop or RV bay, and you are comfortable with a design split between the building maker (the frame) and a foundation engineer.
• Post-frame tends to fit when you want a wood structure on a wide post grid, with isolated footings in place of a continuous perimeter footing, and your builder and building department have done it before.
• Stick framing tends to fit when you want conventional light-frame construction, which the residential code's tables cover, and when the plan you chose is already drawn for it, as ours are. A modern design such as the Blackwood can wear a metal look on any of the three.

What changes when a stick-framed plan goes into a steel or post-frame shell

The rooms, doors, windows and overall shape of a plan can often carry over. The structure behind them is redesigned. For a BarndoVista plan, that work belongs to your builder and engineer, and the editable CAD (DXF) floor plan in the set gives them a file to redraw from. Expect these changes.

• Wall thickness and room sizes. A stick plan assumes a stud wall. Steel columns, built-up posts, girts and added furring each change the wall's thickness, and with it the inside size of rooms, halls and door clearances. Ask your builder to draw the real wall build-up over the plan and recheck every tight room.
• Doors and windows. In post-frame, wall sections between posts carry no roof load, so openings fit most easily between posts. An opening that lands on a post line means moving the opening or the post, or adding a header the engineer sizes. In a steel building, overhead-door openings are framed with members about as deep as the girts. Your builder and engineer fit the plan's openings to the frame grid before anything is ordered.
• Bearing walls and beams. A clear-span steel frame or a post-and-truss frame carries the roof to the outside walls, so interior walls mostly divide rooms. A second floor still needs its own support. If a plan shows an interior bearing line or beam, ask your engineer what it still has to carry in the new frame.
• Lofts, second floors and stairs. A loft is its own structure. In steel it is a mezzanine whose size, height, loads and clearances go into the order documents. One metal building engineer warns that a tapered sidewall column can interfere with a mezzanine, so a straight column may be ordered instead. In post-frame it is a floor framed to the posts and designed by an engineer. The residential code's stair rules stay the same in any frame, so a plan's stair opening usually carries over, though a deeper floor structure can change the headroom.
• Roof details. Dormers and gables, such as those on the Bluegrass Cedar, become extra framing that your engineer carries into the new frame.
• Insulation and air sealing. A stud plan assumes a stud cavity. A steel or post-frame shell needs its own plan for insulation, air barrier and vapor retarder, as the table shows. Our plan sets do not include energy review.
• Foundation. The foundation outline in a plan set is a starting point. A steel frame needs footings or piers designed for its column loads, and post-frame needs post footings or piers, each designed by an engineer for your soil and frost depth.

Steel kits and shell packages

A steel kit, often called a shell package, usually includes the primary frame, purlins and girts, roof and wall panels, trim and fasteners, plus doors and windows only if you order them. It usually leaves out the foundation and anchor bolts, the crew that erects it, insulation and everything inside, so it prices a shell and not a finished home.

A checklist for choosing

1. Call your building department. Ask which code edition and local changes apply, how it reviews post-frame and metal building homes, and what drawings it wants with a permit.
2. Get your site's design loads. Ground snow, wind speed, seismic category and frost depth come from the building department or the ASCE Hazard Tool, an online lookup. They vary a lot: one Wyoming county's table lists a 34 in frost depth, while Minnesota DLI lists 42 to 60 in.
3. Decide the widest room you need and whether you want a loft or second floor. Both change the structure.
4. Ask a lender and an insurer how they treat each system before you buy land or a plan.
5. Have builders price the same plan in each system, including the foundation, insulation and interior framing, so the quotes compare.
6. Ask who designs what: frame, foundation, trusses, any loft, and who coordinates them. A sealed truss covers the truss only.
7. Plan insulation, air barrier and vapor retarder together with the frame. A bare metal skin can sweat.
8. Check local zoning for limits on metal exteriors and setbacks.
9. Confirm what your plan set includes and what your builder will adapt. The list is here.

Where to go next

Browse every design on the floor plans page, look at plans with a shop or modern designs, or read what a shouse is and what a barndominium is. Two guides cover the steps around framing: reading your land first and taking a plan to a builder.