What is a pole barn (and a pole building)?

What a pole barn is

A pole barn is a building framed with large wood posts set in the ground or on concrete, with roof trusses resting on the posts and metal siding and roofing fastened to horizontal boards called girts and purlins. Because the posts carry the load, the walls between them don’t, so the building can span wide with no columns in the middle.

Pole barn, pole building and post-frame building all describe the same method. The name comes from early farm buildings framed with round treated poles, much like utility poles. Today the posts are square, either solid timbers or boards laminated together, and the industry calls the method post-frame. “Barn” describes a use and “pole barn” describes a way of framing, so a pole barn doesn’t have to be a barn: the same frame makes garages, shops, storage buildings, commercial space and homes. Many older barns, by contrast, were timber-framed on stone or masonry foundations.

From our office in Dover, DE, we build pole barns and post-frame buildings across Delaware and Maryland’s Eastern Shore. This guide explains the method the way we’d explain it standing on your lot.

How post-frame construction works

A post-frame building has five working parts: the posts, the footings under them, the roof trusses, the girts and purlins, and the metal skin. Each has one job, and together they make a frame that is stiff, light and efficient to build.

• Posts: solid timbers or laminated columns made of three or four 2x6 or 2x8 boards fastened together, treated for ground contact where they go below grade, and commonly spaced about 8 feet apart.
• Footings: each post sits on a concrete footing at the bottom of its hole, and the hole is backfilled and compacted. Posts can also stand on steel brackets anchored to concrete piers or a slab, which keeps the wood out of the soil.
• Trusses: engineered wood roof trusses rest on the posts or on headers that span between them. They sit farther apart than the trusses in a house, so they’re often doubled at each post.
• Girts and purlins: girts run horizontally across the outside of the posts and carry the wall panels; purlins run across the trusses and carry the roof panels. A treated skirt board runs along the bottom of the wall.
• Metal roofing and siding: ribbed steel panels screwed to the girts and purlins, sold in different thicknesses (gauges, where a lower number means thicker steel) and paint systems. Fastened together, the panels also stiffen the whole frame against wind.

What Delaware codes require of a pole barn

County codes turn those parts into specific requirements, and they differ from county to county, which is one reason a set of plans has to be drawn for your site. Kent County’s building code has its own post-frame sections: footings at least 40 inches below grade and at least 18 inches across, a cleat or other means on each post to resist uplift, a positive connection between the truss carriers and the posts, and steel siding kept from touching treated lumber, because the copper in modern wood treatment can corrode steel. Kent also wants the plans to list the panel gauge and screw pattern.

In Sussex County, a post up to 12 feet tall, measured from the floor to the bottom of the truss, needs at least 36 inches to the bottom of its footing. A taller post goes deeper, a quarter of its height, unless a Delaware architect or engineer designs the footing. Sussex also wants a header inspection before any wall covering goes on, so the framing can be checked while it’s still visible.

How it differs from stick-built and steel buildings

The difference is where the weight goes. A stick-built garage spreads it along walls of studs 16 or 24 inches apart, a steel building carries it on rigid steel frames bolted to engineered concrete, and a pole barn carries it on wood posts spaced several feet apart, each with its own footing.

That changes the foundation. Stick framing needs a footing and foundation wall, or a slab with thickened edges, all the way around. A steel building needs anchor bolts set precisely in concrete piers or a slab sized for its frames. A pole barn needs a footing under each post, and the floor slab, if you want one, can go in after the shell is up. It changes the framing, too: a post-frame wall has a post every 8 feet or so where a stud wall has a stud every 16 or 24 inches, which is much of why post-frame goes up efficiently.

It also changes the inside. Post-frame and steel both leave a clear floor with tall walls and wide door openings, which is why they’re used for shops, farm buildings and storage. Steel’s particular strengths are very wide clear spans and a frame that won’t rot. Stick framing takes drywall straight on the studs, so it finishes like a house without extra framing. We compare all three on cost drivers, insulation, permits and looks in pole barn vs. metal building vs. stick-built garage.

How long a pole barn lasts

A well-built pole barn lasts for decades. How many depends on how well the posts are protected at the ground line, how well water is kept away from the building, and how the roof is looked after.

Posts. Below grade, a post needs preservative treatment rated for ground contact. Laminated columns are often treated only in the lower section that goes in the ground, with dry, untreated boards above, and any cut or notch near the ground should be treated on site. To keep wood out of the soil altogether, posts can stand on brackets anchored to concrete.

Water. Standing water around the posts is what shortens their life. Build on high ground or raise the pad, slope the grade away from the walls, and give roof water somewhere to go. About 17 percent of Delaware lies in the mapped 100-year floodplain, so choose the spot with care. Kent County’s code also marks the county as subject to termite damage, so keep soil, mulch and firewood off the wood.

Roof. Steel roofing needs little care, but not none. Look over the screws and their rubber washers from time to time, since they age before the panels do; keep leaves out of valleys and gutters; and fix loose trim before wind gets under it. Near salt water, ask about panel coatings and fasteners made for salt air. Inside, a condensation barrier under the roof panels, plus vents at the eaves, ridge or cupolas, keeps damp air moving and drips off whatever you store.

What people use pole barns for on Delmarva

Anything that needs a big, open, dry space. Around here that means farm buildings, garages and workshops, horse barns, RV and boat storage, commercial buildings and homes.

Farm buildings came first, and they’re still the classic use. Kent and Sussex counties had more than 160,000 acres in corn for grain between them in the 2022 Census of Agriculture, and the tractors, combines and planters that work those fields need a roof. One farm building we put up holds tractors and combines, a shop for repairs and an office for the farm’s paperwork.

Around the house, people build detached garages and workshops with tall doors and lofts, horse barns with stalls and run-in sheds, tall bays for campers and boats, and open-sided pavilions. Businesses use the same frame for shops, service bays and additions; our commercial work includes a winery’s production addition, a restaurant addition and an equipment dealership. Finish a post-frame shell as a house and you have a barndominium.

When a pole barn makes sense

Post-frame is a natural fit when the building is mostly open space, needs tall walls or wide doors, or might grow later with a lean-to. It takes more planning when the building has to match a brick or sided house under neighborhood design rules, or when the inside will be finished like a home. Both are doable; they change the drawings and the price. If you’ll heat the building, plan the insulation and condensation control with the frame rather than adding them later.

Nearly every pole barn needs a permit. Kent County requires one for a pole building of any size, and Sussex County requires a county building permit for all construction, in towns and out. Start with what will go inside, then size the building around it; our pole barn sizes guide shows what typically fits in common footprints. We draw the building, handle the permit and build it.