Metal Carport Sizes, Roof Styles and Costs for an Open Roof

Metal Carport Sizes, Roof Styles and Costs: an Open Roof on Steel Posts

A metal carport is the cheapest honest way to get a vehicle under a roof. There is no door to buy and no wall sheeting to pay for, so the same money covers a far larger footprint than a closed building does. What you are buying is width, clear height, a roof that sheds what lands on it, and enough anchoring to keep it where you put it.

This is the general page; several neighbours own the narrower searches. A roof sized for a motorhome is an RV Carport, and its enclosed cousin is an RV Garage. The same structure described bay by bay is a Pole Barn Carport. A footprint nobody sells off a shelf is Custom Carports. Steel frames do not rot, warp or feed insects, which is most of the case for metal; whether to build in wood is the Wood Carport page's question. And walls with a door make a building rather than a carport, which the Pole Barn Garage hub prices.

What the Code Actually Calls a Carport

The word gets used loosely; the code does not. Chapter 2 defines a carport as "A structure or portion of a structure, accessory to a Group R-2 or R-3 occupancy, open on at least two sides and unenclosed for at least 50 percent of perimeter". It is for "the parking or storage of passenger motor vehicles", and "Such facility shall not exceed 650 square feet (60.45 m2) in area and one story in height". The wording is New York City's adoption of the model code.

Two sides open, half the perimeter unenclosed, 650 square feet. A double metal carport at 24×24 fits inside that; a triple at 30×30 does not. Past the line it is still perfectly legal — simply an accessory building, reviewed as one.

Wind design uses a second definition, and it is stricter. The same chapter calls an open building "A building having each wall at least 80 percent open". Anything less open is designed as partially enclosed or enclosed, with different pressures and bracing — so sheeting one end of a metal carport is a structural decision before it is a comfort one.

Zoning adds a third meaning. One Ohio city's zoning summary says "A carport must be permanently open on at least 2 sides, no taller than 14 feet, and be physically attached to the building". It lets one reach "into any side yard as close as 3 feet to the side property line". A free-standing roof there is a detached accessory building instead, and "Detached garages must be located in the rear yard."

Metal Carport Sizes: Single, Double, Triple and RV

Start from the vehicle, not the catalogue. The federal accessibility design standards are not a rule for a private driveway, but they are the one published set of parking dimensions anybody can check. "Car parking spaces shall be 96 inches (2440 mm) wide minimum and van parking spaces shall be 132 inches (3350 mm) wide minimum." The aisle beside them "shall be 60 inches (1525 mm) wide minimum".

So a car takes eight feet and a person walking past takes five. A single metal carport at 12 feet wide parks one vehicle and nothing else. At 18 feet there is a walk-around on both sides, which is the difference between parking a car and using the space. A double at 20 feet fits two cars with the doors nearly touching; 24 feet gives the same two cars eight feet of room.

Height is the number most people guess at. The same standards require a vertical clearance of "98 inches (2490 mm) minimum" over a van space and its route. That is eight feet two inches, so a metal carport meant for a van or a roof box wants nine or ten feet of clear height, not eight.

A roof for a motorhome is a different problem. The Federal Highway Administration notes that for vehicle height "State standards range from 13.6 feet to 14.6 feet", and California allows "A house car of a length of up to 45 feet". Fifteen feet of clear height and fifty feet of roof is a different structure from anything in the table, and it is priced separately below.

Roof Styles: Gable, Single Slope and Flat

Roof style is the most searched thing about a metal carport and the least explained. It settles three things: where water and snow go, how much headroom sits over the bay, and how much steel is in the frame.

A gable peaks in the middle and sheds to both eaves. It buys headroom where a raised truck bed or a roof box lives, and throws what lands on it off two sides instead of one. A single slope sheds everything one way, which lets you choose the side. That matters more than it sounds: snow off an eave lands on whatever is parked below, and on the path to the door.

A flat roof is never truly flat, and the code explains why in one line. Susceptible bays "shall be evaluated for ponding instability in accordance with Chapters 7 and 8 of ASCE 7" — ponding being water that collects, deflects the structure and so makes room for more. A low-slope metal carport is a normal thing to build, but not without the slope, the drainage and that evaluation on the drawings.

Snow makes the same argument from the other side. The snow data that must appear on the construction documents includes the "Flat-roof snow load", the "Snow exposure factor", the "Thermal factor" and the "Slope factor(s)". Slope is an input to the design load, not a styling decision taken afterwards.

Gauge, Panel and Coating: What You Are Buying

Two numbers decide what a metal carport is made of, and one reads backwards. Gauge runs inversely to thickness: the lower the number, the thicker the steel. On the cold-formed steel framing tables 12 ga = 0.1017 in and 14 ga = 0.0713 in, so 12-gauge is roughly 40% thicker than 14-gauge, not thinner. If a salesperson has that the wrong way round, so has the quote.

Gauge is nominal rather than exact, too. The framing tables label the gauge column "reference only", and the real figure is the design-thickness designation. Treat a gauge number as a rough class of frame, and read the drawings for the specification.

The panel is a separate question from the frame, and the coating separate again. Zinc-coated sheet is specified under ASTM A653/A653M, "Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process". The aluminium-zinc coating is a different standard, ASTM A792/A792M, "Standard Specification for Steel Sheet, 55 % Aluminum-Zinc Alloy-Coated by the Hot-Dip Process". Ask which a quote means: "galvanized steel" on a brochure is used for both.

None of this is exotic. As the Metal Building Manufacturers Association puts it, "Metal buildings are governed by the same building codes and material standards as other forms of construction". A metal carport answers to what the frame over a warehouse answers to, scaled down.

Open Sides, One Wall, or Closed In

A roof with every side open is one structural animal; the same roof with one end sheeted is another. The code recognises three classes, not a sliding scale: open, partially enclosed, and enclosed — the last being "A building that does not comply with the requirements for open or partially enclosed buildings". Which class a metal carport lands in changes the internal pressure the frame resists.

What a wall buys is real enough. Wind-driven rain and blowing snow reach the sides of a vehicle under any open roof, low winter sun comes under the eave all afternoon, and nothing is locked. One wall on the weather side fixes most of that for a fraction of what closing it in costs.

What it costs is the enclosure class and the bracing that follows, so decide it before the drawings are sealed rather than screwing panels on two summers later. Adding sheeting to a metal carport engineered as an open building changes the loads it was designed for. If the honest answer is walls all round with a door, stop pricing a roof and price a building.

Wind and Snow on a Roof With No Walls

The code requires that "Wind loads on every building or structure shall be determined in accordance with Chapters 26 to 31 of ASCE 7", and the enclosure class is the first thing the engineer reads. A closed building resists part of that through its walls. A metal carport has none, so the roof and the columns carry all of it.

The code then says what the structure has to do about it. Members "shall be anchored to resist wind-induced overturning, uplift and sliding and to provide continuous load paths for these forces to the foundation". And: "Anchorage of the roof to walls and columns, and of walls and columns to foundations, shall be provided to resist the uplift and sliding forces". Uplift, not weight, governs here.

The Department of Energy's Building America guidance is blunter about where these come apart. "Strong winds can separate the roof structure of attached porches and carports from the supporting structure," it says, and the joints between members "are commonly the weakest link within a load path". Its instruction: "Install a metal connector at each column-to-foundation connection".

Snow is the load people assume is the same for any roof of the same shape. It is not. The code's thermal factor table sets the factor at 1.0 for "All structures except as indicated below" and 1.2 for "Unheated structures". A metal carport is unheated by definition, so its design snow load is a fifth higher.

There is no national wind number to design to, and no national snow number either. Both are site-specific, and the ASCE Hazard Tool returns them for an exact address. Give the supplier the address and have the design figures printed on the drawings.

Anchoring on Concrete, Asphalt and Bare Ground

A metal carport is held down more than it is held up, and the three surfaces already in most driveways hold down very differently.

On bare ground, columns can be embedded. The code has a section for exactly that, covering "Designs to resist both axial and lateral loads employing posts or poles as columns embedded in earth or in concrete footings in earth". It says "The depth to resist lateral loads shall be determined using the design criteria" set out there. Embedment comes from the soil and the force at the top of the column, not from round numbers.

On concrete, the column lands on a bracket and the anchors go into the slab — which works only if the slab was poured to take it. A thin driveway slab is not a foundation, and thickened edges or footings under the columns have to be there before the steel arrives. Ask whether the anchor design assumes a slab or a footing.

Asphalt is the surface that catches people out, and no code writes a rule for it because there is nothing there to write one about. It is a wearing course over a base, while a footing has to bear on undisturbed native soil, engineered fill or rock. Anchoring a metal carport to a driveway surface anchors it to nothing: core through and land the columns on something that carries load.

Frost is the other half of the foundation question. The code requires that "foundations and other permanent supports of buildings and structures shall be protected from frost", by "Extending below the frost line of the locality" or by an engineered alternative. Only the building department can give you the depth it enforces.

Erection is worth pricing before doing it yourself. Steel erection "is one of the top 10 most hazardous occupations according to BLS fatality data year after year", the Labor Department says. The work it covers runs to "heavy duty high rise structures, metal buildings and even signs". The $2,900–$6,900 erection line at 576 square feet buys a crew who do it weekly.

What a Metal Carport Costs

A metal post-frame kit is priced by floor area: $13–$25 per square foot under 600 square feet, $9–$32 per square foot from 600 to 1,500. An open roof is the least a metal post-frame structure prices — the wall sheeting and doors are not in it — so a metal carport sits toward the bottom of its range.

Take the 24×24 double as the worked example. The kit is one line of the bill; the pad, the erection, the site work and the permit are the rest.

That is $27 to $64 per square foot, and the spread is wider than it looks for a reason worth knowing. Two of those five lines barely shrink with the building. Site preparation at $1,300–$5,600 and permits at $500–$3,100 cost much the same for a single as for a triple, so a small metal carport carries them as a far larger share of its bill.

Park on gravel instead and the $3,500–$6,900 slab line comes off: $12,200–$30,000. The kit range at this footprint runs $7,500 to $14,400 — the same square footage, a very different structure over it. Clear height and clear span move a quote most: both put steel into the frame rather than area onto the roof.

Permits, Setbacks and the Height Cap

Assume a permit, and settle zoning before the structural question. The International Code Council says as much: "As a model code, the IBC is intended to be adopted in accordance with the laws and procedures of a governmental jurisdiction". It adds that "some jurisdictions amend the code in the process to reflect local practices and laws". The version enforced in your town counts.

Height is where a metal carport meets local rules first. The same Ohio city caps accessory buildings at "1-1/2 stories or 14 feet in height", and a carport at "no taller than 14 feet". For a car at eight or nine feet of clear height that is no constraint. For a roof tall enough for a motorhome, it is the whole project.

Setbacks bite a carport harder than a garage. Maricopa County's zoning directive allows detached accessory structures in a required rear or side yard. But they "shall not occupy more than 30% of any required yard and shall not be nearer than three feet to any side or rear lot line". A metal carport goes beside the house almost by definition, which is where a side-yard setback applies.

Three questions at the planning counter: what height is allowed for a detached accessory structure here, what setback applies, and does an open roof count toward lot coverage. Ask a homeowners' association the same three, in writing.

Regional Cost Differences

What you would pay above is the national figure for a metal carport this size. Region moves it: labor rates, wind and snow codes, seismic design and freight from the mill change the price of the same structure from one part of the country to another.

South and Southeast markets are the baseline this page already prices to: $15,700–$36,900 installed at 24×24. Midwest labor rates and mill freight push that roughly 5–10% higher. Northeast labor rates, plus the heavier wind and snow loads already discussed above, add roughly 15–25%. The West runs highest of the four — the same labor and code pressures as the Northeast, plus the longest freight from the mill and, in seismic zones, added engineering — without one band that fits every state in it.

Wind speed, ground snow load and mill freight all shift from one county to the next inside the same region. Give a supplier the address and price that address, rather than shopping the regional band on its own.

The gap widens at the smaller sizes on the table above too: a 12×20 carries the same site preparation and permit lines as a 30×30, so the regional adjustment lands on a larger share of a small carport's total than a large one's.

Return on Investment

A metal carport has no insulation to pay back, so there is no energy-saving payback to run here. The return this buyer weighs is plainer: what a roof over the vehicle is worth against parking in the open.

What can be said without a source: a vehicle under any roof sheds direct sun, rain and falling debris that one parked in the open does not. Whether that is worth $12,200 or $36,900 is a question about the vehicle and the climate, not about the carport.

Financing

A metal carport finances more like a driveway or a garage door than like a commercial building, and most buyers use one of two paths.

Most kit sellers offer installment financing on the kit itself, the way a dealer finances an attachment or an addition — ask what the supplier offers before shopping a loan elsewhere. It is usually the fastest path, since it ties directly to the order rather than a separate application.

Where the carport goes in alongside a larger property project — a new driveway, a slab, an addition — a home-equity loan or line of credit can fold the cost into financing already tied to the property, and an owner with equity in the property can qualify.

Down payment requirements vary by lender and by how the loan is structured. Confirm them before ordering, not after.

From Quote to Occupancy

The sections above already cover who should hire the erection and who should not. What they do not lay out is the order the work happens in, whichever way that decision goes. Laid out end to end, it runs six stages from a sealed drawing to a vehicle parked underneath.

1. Get sealed drawings and a wind- and snow-specific quote for the address.
2. Pull the permit and confirm setbacks and the height limit at the planning counter.
3. Excavate and set footings, piers or embedded posts to the local frost depth.
4. Erect the columns and roof.
5. Pour the slab, or finish grading if building on gravel.
6. Final inspection, then park under it.

Steps three and four are where the anchoring and erection sections above matter most: footing depth and the column-to-foundation connection are the two points this page already flags as the ones worth getting right.

A metal carport is a short list of decisions with one expensive mistake available in each: clear width, clear height, the roof style and where it throws what lands on it, and what holds the thing down. The structure is the predictable part, at $15,700–$36,900 installed at 24×24, or less on gravel.

So take them in that order. Measure the vehicles and add the walking room, and set the clear height from the tallest thing you park. Get the design wind speed and ground snow load for the address, settle height and setbacks with the planning counter, then ask suppliers for clear dimensions and the anchoring detail. Quotes that answer those can be compared; the rest cannot.

Related Resources

• RV Carport
• Pole Barn Carport
• Wood Carport
• Custom Carports
• Pole Barn Garage
• Pole Barn Cost Estimator
• 3D Pole Barn Designer