Most barndominium steel frame Central Texas projects that go wrong go wrong at the slab, before any steel shows up. Picture a hypothetical Saturday outside Bertram. The slab went in three weeks ago and looks good: flat, clean edges, anchor bolts standing up in neat rows. The frame arrives, the crew sets the first column, and the base plate holes miss the bolts by an inch and a half. Nobody did anything obviously wrong. The slab crew poured to the drawing they had. The frame was built to a newer drawing. That gap between two sets of paper is the most common way a barndominium steel frame in Central Texas goes sideways.
The through-line of this list is simple: the slab is the first part of the frame. Concrete locks in whatever the frame design says at the moment of the pour. Every decision below has to be settled, drawn and handed to both the foundation crew and the steel crew before the concrete truck is called. Change any of them after the pour and you are paying for it with a core drill, a cutting torch or an engineer's revision.
If you are still at the stage of picking a site and a building type, start with the broader landowner's guide to planning a steel building, barndominium or metal shop in Central Texas. This article picks up where that one stops: the building type is chosen, and now the frame and the foundation have to agree.
1. Which steel frame style is the barndominium actually using?
"Metal barndominium" covers several very different structures, and each puts different demands on the slab.
- Rigid frame (red iron). Tapered, built-up I-beam or W-shape columns and rafters welded into portal frames, usually 20 to 25 feet apart. Each column lands on a base plate with a group of four or more anchor bolts. This is the frame style that makes wide open interiors possible.
- Tube steel frame. Square or rectangular tube columns and trusses, common on smaller barndos, carports and covered structures. Lighter reactions at the base, but more columns, so more bolt locations to get right.
- Hybrid. Rigid frames for the main living and shop span, with tube steel porches, lean-tos or a carport wing bolted on. Very common in the Hill Country, and the one most likely to produce two sets of anchor bolt drawings that never got merged.
The frame style decides how many bolts go in the slab, how big the footings under each column need to be, and whether the slab has to resist outward thrust at the column base. A rigid frame pushes outward at its feet under roof load. That thrust is usually carried by hairpin rebar or tie rods cast into the slab, running from each column back into the floor. If the frame style changes from tube steel to rigid frame after the pour, those hairpins are not there, and there is no clean way to add them.
Planning something like this? Send the shop your drawings for a written quote.
2. How wide a clear span does the barndominium floor plan need?
Clear span is the width between columns with nothing in the middle. Owners pick it from the shop side of the plan: a gooseneck trailer, a tractor with a front loader, a boat, an RV door. Then the living quarters get fitted inside.
Here is why it matters for the slab. A 40-foot clear span and a 60-foot clear span can both be built, but they put very different loads on the column footings, and the wider span pushes harder on the hairpins. Adding one interior column line, say between the living side and the shop side, can shrink the main frame members and the footings. But that interior column needs its own footing and its own bolt group poured in the right spot.
Decide these on paper before anything else:
- Overall width and length, measured to the outside of the steel, not the outside of the sheeting.
- Bay spacing along the length, which sets where every column and every bolt group lands.
- Any interior columns, including ones that will end up hidden inside a wall between the living area and the shop.
- Where the big doors go. A 14-foot overhead door needs framed openings and jambs, and those jambs often land on the slab with their own anchors.
3. Where do the loft, porches and lean-tos tie into the frame?
Lofts and mezzanines are standard in barndominiums. A loft bedroom or a storage mezzanine hung off the main frame adds columns, beams and floor load. A deep wraparound porch adds a row of posts outside the main building line, often on its own footings. A lean-to for equipment adds another line of columns and changes the load on the main columns it hangs from.
Each of these has two parts that must match: the steel that attaches to the main frame, and the footing or bolt group in the concrete. The common miss is a porch that was "added later" in the drawings. The slab crew never saw it, so the porch posts end up on post-installed epoxy anchors in a thin edge of slab, when the engineer really wanted a thickened footing.
Eave height belongs in this decision too. A higher eave for a loft or a tall shop door means longer columns, more wind load on the walls, and bigger reactions at the base. Pick the eave height before the footing sizes are set, not after.
4. What loads should the barndominium steel frame be designed for in Central Texas?
Every structural steel frame is designed for a set of loads, and in the United States those loads come from ASCE 7, the standard for minimum design loads on buildings. For a Central Texas barndominium the ones that drive the design are:
- Wind. The big one. ASCE 7 wind speeds and the site's exposure category decide how hard the wind pulls up on the roof and pushes on the walls. An open hilltop in Burnet County sees a different exposure than a lot tucked into the trees in Leander. Uplift at the column base is what the anchor bolts and footings resist, so wind loads directly set bolt size and embedment.
- Collateral load. The weight of everything hung from the steel: ceilings, insulation, ductwork, HVAC units, lighting, and interior finishes. A barndominium with sheetrock ceilings and hung ductwork needs a real collateral load in the design. A frame designed as a bare equipment shed and later finished as a house is a common mistake.
- Roof live load and hail. Snow is a small factor here. Hail is not a load case the frame is sized for in the same way, but it drives the choice of roof panel gauge and finish, and panel choice affects purlin spacing.
- Loft and mezzanine floor loads, from decision 3.
The loads come out of the engineer's calculations as column reactions: the up, down and sideways forces at each column base. Those reactions are what the foundation engineer uses to size footings, hairpins and bolt embedment. If the foundation is designed before the frame reactions exist, the foundation is a guess. Ask for the reactions in writing and make sure the foundation design references them.
Steel connections welded in the shop or in the field on a structural frame are normally done to the AWS D1.1 structural welding code. That is worth asking about, but it cannot fix a bolt pattern that was poured wrong.
5. Who draws the steel frame's anchor bolt plan, and who checks it?
The anchor bolt plan is the one drawing that both crews must build to. It shows every bolt group, the bolt diameter and length, the embedment, how far each bolt sticks up above the concrete (projection), and the dimensions from each group to the building lines.
This drawing should come from the frame design side, because the frame design is what fixes the base plate holes. The foundation crew then builds to it. The problems start when there are two versions going around, or when the slab crew works off a sales sketch.
The tolerances are tighter than most owners expect. Under the AISC Code of Standard Practice, anchor rods within a single bolt group should be within 1/8 inch center to center, adjacent groups within 1/4 inch, and the accumulated error along a column line within 1/4 inch per 100 feet, capped at 1 inch. Those numbers are why good slab crews use a bolt template: a plywood or steel plate drilled to match the base plate, holding the bolts plumb and at the right height while the concrete is placed.
Before the pour, ask these questions out loud:
- Is the anchor bolt plan the latest revision, and does it carry the same revision number the frame is being built to?
- Does it include the porch posts, lean-to columns, door jambs and any interior columns?
- Who is setting the templates, and who checks bolt locations against the plan before the truck shows up?
- Are hairpins or tie rods shown on the foundation plan, and do they line up with the column lines?
- Is the slab dimension to the outside of the steel, with any perimeter notch for the wall sheeting shown?
That last one catches a lot of people. Metal building slabs are often poured with a small notch or brick ledge around the edge so the wall panels lap down past the top of the slab. Rain runs off the outside of the building instead of across the floor. Pour the slab too big, and the sheeting sits on top of the concrete and water gets in. Pour it too small, and the base plates hang over the edge.
6. How long should the slab cure before the steel frame goes up?
Concrete does not reach full strength the day after it is poured. Anchor bolts in green concrete can pull out or crack the concrete around them when the frame is stood up, braced and tightened. The foundation engineer should say what strength the concrete needs to reach before steel is erected, and many projects confirm it with cylinder tests at set ages.
Central Texas summer makes this harder. Hot, dry, windy afternoons pull water out of fresh concrete fast, which leads to cracking and weak surfaces. Hot-weather concreting practice under ACI 305 is why slab crews here pour at first light in July and August and keep the slab wet or sealed with curing compound. Plan the frame delivery around the cure, not the other way around. A frame that shows up early sits in the yard. A frame rushed onto an uncured slab is a risk to the bolts and the concrete.
Timing cuts the other way too. If the frame is being fabricated to order, the shop needs final drawings early enough to cut, weld, prime and load out by the date the slab will be ready. That is the reason both schedules have to come from the same set of final drawings.
7. What has to be in the slab before the steel arrives?
Everything that runs under or through the floor must be in place before concrete. For a barndominium that list is longer than for a plain shop:
- Plumbing rough-in for kitchen, baths and laundry, placed to the final floor plan, not a draft.
- Electrical and data conduit for any floor outlets, the shop side's welder or compressor circuits, and any conduit that has to reach a column-mounted panel.
- Septic and water line stub-outs. Outside city service, the septic system falls under on-site sewage facility rules. In Texas those are regulated by TCEQ's on-site sewage facility program, often administered through the county. The permitted system layout controls where the drain lines leave the slab.
- Footings and piers matched to the soil. East of I-35 in Williamson County you are often on expansive Blackland Prairie clay that swells and shrinks with rain and drought. West toward Liberty Hill, Bertram and Marble Falls you are more often on caliche and limestone, where footings may be cut or drilled into rock. A geotechnical report tells the foundation engineer which one you have, and the column footings follow from it.
- Hairpins, tie rods and thickened edges from decisions 1 and 5.
Which permits and approvals apply to a barndominium in Central Texas?
The answer depends on exactly where the lot sits, and that line keeps moving. According to the U.S. Census Bureau, Williamson County counted 609,017 residents in the 2020 Census, and growth like that keeps pushing city limits and extraterritorial jurisdictions outward into land that used to be plain county ground.
In general terms:
- Inside city limits (Liberty Hill, Leander, Georgetown, Cedar Park, Burnet, Marble Falls and others), the city building department typically requires a building permit, plan review and inspections under its adopted codes.
- In unincorporated county areas, many Texas counties do not issue a building permit for a single-family home. County development services still handle things like septic permits, floodplain development permits and driveway access, and those apply to Williamson, Travis and Burnet counties alike.
- In an ETJ, subdivision and platting rules may apply even without a building permit. A 2023 state law, Senate Bill 2038, created a petition process to release land from a city's ETJ, so do not assume a lot's status from an old survey.
Lenders and insurers often want engineer-stamped frame and foundation drawings even where no permit is required. Confirm the rules for your parcel with the county or city before you design, and have a licensed engineer design the frame and foundation. Nothing here is a legal or engineering answer for a specific site.
The handoff that keeps the frame and foundation crews in sync
All seven decisions end in one handoff: a final, dated set of frame drawings, reactions and anchor bolt plan that the foundation engineer, the slab crew and the steel fabricator all hold at the same time. When a change comes up, and one always does, it goes to the drawing first and then to both crews. Never to one crew by phone.
If the drawings are in hand and the slab is scheduled, TG Welding in Liberty Hill builds structural steel and steel buildings, covered structures and outdoor steel on a written PO in its Highway 183 bay, then loads it out or sets it on the customer's slab. The shop's process from drawings to written quote to install starts with the same set of papers this article describes, and you can see examples of completed steel work before you plan your own.
Barndominium steel frame questions owners ask
Can I pour the slab first and figure out the frame later?
You can, but you should not. The frame design sets the bolt locations, footing sizes and hairpins. Pouring first means the frame has to be designed around concrete that may not fit it, which often means epoxy anchors, extra footings or a redesign.
What happens if the anchor bolts are poured in the wrong place?
It depends on how far off they are and what the engineer allows. Small misses are sometimes handled by slotting or re-drilling base plates. Large misses can mean cutting bolts off and installing engineered post-installed anchors, which needs an engineer's sign-off. Either way it costs time on site.
Does a barndominium in unincorporated Williamson County need engineered drawings?
There may be no county building permit for a single-family home, but septic, floodplain and driveway rules still apply, and lenders or insurers often ask for stamped drawings. Confirm with Williamson County and a licensed engineer for your parcel.
Is a tube steel frame strong enough for a barndominium?
Tube steel frames work well for smaller spans, porches, carports and lean-tos. Wide clear spans and tall eaves usually call for a rigid frame. The engineer's load calculations for your site decide it, not the frame style's reputation.
How far ahead should the steel fabricator have final drawings?
Early enough to cut, weld, prime and load out by the date the slab has cured to the strength the engineer requires. Get the fabricator the final drawings when the foundation is designed, not when the slab is poured.
Frequently asked questions
Can I pour the slab first and figure out the barndominium steel frame later?
You can, but you should not. The frame design sets the bolt locations, footing sizes and hairpins. Pouring first means the frame has to be designed around concrete that may not fit it, which often means epoxy anchors, extra footings or a redesign.
What happens if the anchor bolts are poured in the wrong place?
It depends on how far off they are and what the engineer allows. Small misses are sometimes handled by slotting or re-drilling base plates. Large misses can mean cutting bolts off and installing engineered post-installed anchors, which needs an engineer's sign-off.
Does a barndominium in unincorporated Williamson County need engineered drawings?
There may be no county building permit for a single-family home, but septic, floodplain and driveway rules still apply, and lenders or insurers often ask for stamped drawings. Confirm with Williamson County and a licensed engineer for your parcel.
Is a tube steel frame strong enough for a barndominium?
Tube steel frames work well for smaller spans, porches, carports and lean-tos. Wide clear spans and tall eaves usually call for a rigid frame. The engineer's load calculations for your site decide it.
How far ahead should the steel fabricator have final drawings?
Early enough to cut, weld, prime and load out by the date the slab has cured to the strength the engineer requires. Get the fabricator the final drawings when the foundation is designed, not when the slab is poured.