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What is the cost for a garage addition?

United States: homeowner survey

Households in the American Housing Survey that hired out adding an attached garage or a carport, which the survey counts as one job type, reported a median of $5,800; the typical range (middle half of 117 American Housing Survey data points, the United States, 2021-2023) was $2,400 to $22,200.

How measured: hired-out finished jobs, survey-weighted, not adjusted for inflation. Source: U.S. Census Bureau, American Housing Survey 2023, data read 17 October 2026.

These figures are estimates from U.S. Census Bureau, American Housing Survey 2023, data years 2021-2023, read 17 October 2026, for the United States. They are not a quote, and they are not a promise of what any contractor on InstaBids will charge. Your price depends on your home, the materials and the contractor. Get written bids before you decide.

InstaBids is a written-bid marketplace for home jobs: you, or your AI assistant, describe it once; contractors bid in writing on that scope; you choose who gets your number.

Researched by the InstaBids editorial team. Last checked: 17 October 2026 Updated 2026-10-17

What does the attached garage addition cost on this page cover?

The figures above are what households that hired out the job reported for adding an attached garage or a carport, because the survey item reads "Added attached garage or carport" and counts the two together. A detached garage falls under a separate survey item, "Added or replaced shed, detached garage, or other building", and is not in the figures above.

Source: U.S. Census Bureau, AHS 2023 Value Labels Package, read 17 October 2026.

Of the finished attached garage and carport jobs in the survey whose cost the household reported itself, rather than one edited or filled in by the Census Bureau, 65 percent were hired out, counting each household for the number of homes it stands for in the survey. The figures above count only those hired-out jobs. That share is higher than for adding or replacing a shed, detached garage or other building (55 percent) and lower than for adding or replacing roofing (87 percent).

How much does a carport cost?

The figures above are the survey's answer for one job type that counts an added attached garage and an added carport together, and the survey gives no figure for a carport alone.

Source: U.S. Census Bureau, AHS 2023 Value Labels Package, read 17 October 2026.

The City of San Diego's carport bulletin, citing the California Residential Code, defines a carport as a covered parking structure for a one- or two-family home, freestanding or attached, no more than one thousand square feet and one story, entirely open on two or more sides apart from its supports, with no enclosed use above. San Diego says a carport that does not meet that definition must follow all the rules for a private garage.

Source: City of San Diego, Development Services, Information Bulletin 205: Carports, read 17 October 2026.

San Diego requires a building permit for any new carport and for repairing or enclosing an existing one, and the work is not complete until it passes the city's final inspection.

Source: City of San Diego, Development Services, Information Bulletin 205: Carports, read 17 October 2026.

Apart from how much it costs, what does it take to build a garage addition?

In Grand Rapids, Michigan, the city's garage permit guide says a building permit is required to build a garage and that an attached garage is treated as an addition to the house.

Source: City of Grand Rapids (Michigan) Development Center, Permit Guide: Garage Construction, read 17 October 2026.

The Grand Rapids guide asks for building plans that show the proposed structure in detail and a site plan with property lines, existing and proposed structures, driveways, sidewalks, streets, easements and overhead power lines. It notes that the city's zoning ordinance affects where a garage may go.

Source: City of Grand Rapids (Michigan) Development Center, Permit Guide: Garage Construction, read 17 October 2026.

For an attached garage, the same guide calls for at least 1/2-inch gypsum board (drywall) on the garage side between the garage and the house and its attic, 5/8-inch Type X (fire-resistant) gypsum board when rooms people live in sit above the garage, and doors into the house of solid wood or steel at least 1 3/8 inches thick or rated for 20 minutes of fire, with no windows in those doors or in shared walls.

Source: City of Grand Rapids (Michigan) Development Center, Permit Guide: Garage Construction, read 17 October 2026.

The Building America Solution Center of the U.S. Department of Energy says drywall put up to meet local fire codes is not the same as air sealing, and that every opening for wiring, pipes or ducts through those walls and ceilings needs a sealant such as caulk or canned spray foam.

Source: DOE Building America Solution Center (PNNL), Air Sealing Attached Garage, read 17 October 2026.

On hiring, the California Attorney General's consumer page advises taking your time before you decide to hire a contractor, getting multiple bids, checking references and hiring only contractors who hold a licence. It warns that a contractor who pushes for an immediate decision makes it impossible to get competing bids, check licences or review references.

Source: State of California, Office of the Attorney General, Contractors (consumer page), read 17 October 2026.

How is a garage addition sealed off from the house?

The Department of Energy guide calls isolating an attached garage from the living space critical for keeping carbon monoxide and other contaminants out of the home, and asks for a continuous rigid air barrier between the garage and the heated and cooled part of the house.

Source: DOE Building America Solution Center (PNNL), Air Sealing Attached Garage, read 17 October 2026.

EPA lists exhaust from attached garages among the sources of carbon monoxide in its indoor air guidance, and a NIST field study of five homes found the garage at least twice as leaky as the house in every one.

Source: U.S. EPA, Carbon Monoxide's Impact on Indoor Air Quality, read 16 October 2026.
Source: NIST, Air and Pollutant Transport From Attached Garages to Residential Living Spaces: Literature Review and Field Tests (publication page), read 17 October 2026.

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Sources for the figures on this page