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Home / Articles / Single Leg vs Double Leg Metal Buildings: When You Need the Upgrade
Single Leg Vs Double Leg
31Aug 2026Metal Buildings

Single Leg vs Double Leg Metal Buildings: When You Need the Upgrade

Single Leg Vs Double Leg

When planning a metal building with a lean-to or covered extension, one of the first decisions you may face is whether a single-leg or double-leg design makes more sense. While the difference may sound simple, the number of legs supporting the structure can affect everything from available space and vehicle access to overall stability, appearance, and cost. Choosing the right configuration early can help guarantee your building performs the way you expect.

This guide will compare single-leg and double-leg metal buildings and explain when the added support, space, and versatility are worth the investment.

Key highlights

  • A single leg is one piece of galvanized square tubing running from your base rail up to the truss. A double leg is two of those tubes welded together into one column.
  • Double legs are typically standard once your sidewall height passes 12 feet, because a taller upright carries more load at its base.
  • Adding solar panels, running a wide clear span, or building in high-wind country can all trigger the upgrade regardless of height.
  • Upright spacing stays the same either way. We don't add more legs, we make each one thicker.
  • You can't convert a single leg building to double legs after it's installed. This is a decision you make at quote time.
  • Under 12 feet on a standard-width structure, a single leg is engineered to do the job and the upgrade is money you don't need to spend.
  • Not sure which applies to your site? Call us at (866) 681-7846 and we'll look up your local requirements before you order.

What a double leg actually is

Every building we put up starts with the same skeleton. A base rail sits on your ground or your slab, uprights stand off that rail, and trusses tie the whole thing across the top. The upright is what people call the leg.

Our framing is 2 1/2 inch by 2 1/2 inch galvanized square steel tubing in 14 gauge, which is the industry standard. We also offer 12 gauge if you want thicker walls on that tubing.

A single leg is one length of that tubing. Simple, proven, and what most residential carports and garages run.

A double leg is two of those same tubes welded together side by side, so every upright along your perimeter is 2 1/2 inches by 5 inches instead of 2 1/2 by 2 1/2. Same spacing along the wall. Same tubing. Twice the column.

Why we don't just add more legs instead

If you need more support, why not put uprights every 3 feet instead of every 5? Because the deciding factor is how much bending force lands on each individual upright.

A taller leg has more bending force working against it at the base. So we thicken each column instead of crowding your wall with extra uprights that get in the way of backing a trailer in.

Single leg vs double leg at a glance

Single leg Double leg
Construction One piece of galvanized square tubing Two tubes welded together as one column
Column footprint 2 1/2" x 2 1/2" 2 1/2" x 5"
Typical sidewall range Up to 12 feet 12 feet and above
Upright spacing Standard along the base rail Same standard spacing
Resistance to side loading Engineered for standard residential heights Noticeably stiffer at the base
Best fit Car and truck covers, standard garages, storage buildings Tall RV covers, solar-ready roofs, high-wind sites, wide clear spans
Can it be added later? No No
Cost impact Included in base pricing Additional, varies by size and quantity

When you need double legs

Four situations push a build into double leg territory. You might hit one of them or all four:

Your sidewall goes above 12 feet

Once you cross a 12-foot leg height, we're generally building with double uprights. A 12-foot sidewall on an A-frame vertical structure puts your peak somewhere around 14 1/2 feet. That's the height most fifth wheels and Class A motorhomes need once you account for the air conditioner on the roof.

So the moment you size a cover to actually clear your rig, you're at the height where the frame changes. That second column is what keeps a 13-foot structure behaving like a 9-foot one when the wind picks up.

Planning a tall RV cover? See the 18x30x13 A-frame vertical-roof RV carport for a real product example, then compare clearance needs in our RV cover height by camper class guide.

If you're sizing an RV cover and haven't nailed down your height yet, our guide on RV cover height by camper class walks through the clearance you need by rig type.

You're mounting solar panels on the roof

Panels add weight that never comes off. They also change how wind moves across your roof, since an array catches air differently than bare steel.

Doubling the uprights while the building is still on paper costs a fraction of what it costs to find out the frame won't carry the load after the array is up there. If solar is anywhere in your five-year plan, tell us at quote time even if you're not buying panels yet.

You're building where the wind runs hard

Every building we sell is engineered to meet the wind and snow requirements where it's going. We look up your address before we quote you, and that local code drives the specs.

In some parts of the country, those requirements call for double legs on structures that would run single legs elsewhere. Coastal Alabama. The Texas panhandle. Open ground in Kansas and Colorado.

If your site sits exposed with nothing breaking the wind, mention it. Aerial photos don't show a tree line that came down two years ago.

You're going wide

Once your building passes 30 feet in width, you're into commercial framing. The truss has to span all that distance with nothing holding up the middle, so the whole structure gets heavier, and the uprights carrying that truss get doubled along the perimeter.

On some commercial builds we go a step further to a ladder-style leg, which is a wider column with cross pieces welded through it. Which one your building gets depends on what the engineer specifies for your state and your span. Our breakdown of how wide a clear span metal building can be covers where those width thresholds land.

Need a wide commercial example? Review the 60x70 commercial clear-span building, or browse commercial metal buildings for more layouts.

When a single leg is plenty

Plenty of buildings don't need this upgrade, and we'll tell you so. A 20x20 two-car carport with a 9-foot leg on a residential lot? Single leg, engineered for your local code, done. A 12x20 storage building for a mower and yard tools? Same. A 24x25 cover for a truck and an SUV at 10 feet? Single leg handles it.

We size the frame to the job. If your sidewall sits at or under 12 feet, your width stays under 30, and there's nothing going on the roof, the standard frame is what your local code calls for and paying past that doesn't buy you anything you'll use.

We do build some structures with double legs at lower heights when the design calls for it. Our 20x20 two car carport runs double legs and base rails at a 10-foot height. So don't assume height alone decides it. Ask.

Can you add double legs after installation?

No. Once your building is up, anchored, and paneled, converting single uprights to doubles means taking the structure apart.

Same goes for adding length, adding side panels, or raising the height. Everything structural happens before the crew shows up. Electrical, interior finishing, and insulation work can wait. The frame can't. Size for the vehicle you might own in five years.

Build the layout before you order: use the 3D Estimator & Color Planner, then request a quote once the size, height, roof style, doors, windows, and layout fit the way you plan to use it.

How your legs and your anchors work together

Strong uprights don't help you much if the building can lift off the ground. We stake structures down with rebar and set 30-inch auger-style anchors, which thread into the soil and resist pulling up. On a concrete slab, we run expansion bolts down through the base rail into the pad.

Those two systems do different jobs. Rebar stakes hold your building in position. Auger anchors fight uplift, which is what wind does to a roof.

Taller building, more sail area, more uplift. A double leg build deserves a hard look at the anchoring too. Our guide on securing your metal building with a proper anchoring system goes deeper on how those anchors work in different soil.

Frequently asked questions

What is a double leg on a metal carport?

A double leg is two pieces of galvanized square steel tubing welded together to form one upright, so each column measures 2 1/2 inches by 5 inches instead of 2 1/2 by 2 1/2. Spacing along the base rail stays the same as a single leg building. The upgrade thickens each column rather than adding more of them.

Do I need double legs on a 14-foot carport?

Almost certainly yes. We generally build with double uprights once sidewall height passes 12 feet. Anything at 13 or 14 feet is tall enough that the base of each leg takes real bending force in a wind event. Your local wind and snow requirements make the final call, and we look those up before quoting.

Are double legs worth the extra cost?

If your building is tall, wide, carrying rooftop weight, or sitting on exposed ground, yes. The upgrade costs a small percentage of the build and it's the difference between a structure that flexes and one that doesn't. On a standard 9 or 10-foot residential carport, the money is better spent elsewhere.

Can I add a second leg to my carport later?

No. Converting single uprights to doubles requires disassembling the frame, so it isn't something a crew can do on an existing building. Decide before you sign.

Does a double leg change how many uprights my building has?

No. Spacing along the base rail stays the same. We make each column thicker rather than adding more of them, which keeps your openings clear for backing in a trailer or an RV.

Do 12 gauge framing and double legs do the same thing?

They're separate upgrades that stack. Gauge is the wall thickness of the tubing itself, where 12 gauge is thicker steel than the standard 14 gauge. Double legs are about how many tubes make up each column. You can order 14 gauge with double legs, 12 gauge with single legs, or both together. Our post on 14 gauge vs 12 gauge framing breaks down the tubing side.

What leg style do commercial buildings use?

Buildings over 30 feet wide move into commercial framing, where uprights are doubled or built as a wider ladder-style column depending on what your engineer specifies for the span and your state.

Planning the purchase? Financing is available, and Rent-To-Own is available for buyers who want another payment path. Pricing varies by building size, options, and location.

Making the call

If your sidewall is 12 feet or less, your building is under 30 feet wide, and nothing is going on the roof, a single leg frame engineered to your local code is what you need. Go taller, go wider, add solar, or build on exposed ground, and double legs stop being optional.

The one thing you can't do is change your mind after the crew leaves. Tell us what you're parking, where you're parking it, and what you might add down the road, and we'll spec the frame around it.

Ready to get started? Design Your Building online, request a quote, or call Coast to Coast Carports at (866) 681-7846 and we'll look up your local requirements while you're on the phone.

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