Quick answer
A 3 car garage cost typically runs $45 to $90 per square foot in 2025, so a 900 sq ft detached garage lands near $40,000 to $81,000. Attached garages often price lower per square foot because they share the house foundation, roof plane, and utility runs.
- Budget $45–$90 per sq ft for a detached 3-car garage; attached builds often run $35–$70 per sq ft.
- A 30x30 (900 sq ft) detached garage commonly totals $40,000–$81,000 before sitework surprises.
- The slab, shell, and three overhead doors usually account for 60–70% of the total.
- Long driveways, poor soils, and utility extensions can add more than the garage shell itself.
What Drives 3 Car Garage Cost in 2025?
A detached 3 car garage typically costs $45,000–$120,000, or $55–$110 per square foot, depending on size, finish level, and region. That range covers a basic, unfinished structure with asphalt or gravel apron. Attached garages often fall outside this range because they share the house foundation, roof plane, and utility runs, which changes how the garage cost is priced.
The 3 car garage cost is driven by five levers: footprint size, foundation type, wall height and roof structure, door count and type, and whether the space is finished or conditioned. A 30x30 slab-on-grade with three 9-foot doors prices very differently from a 32x40 with a full second-floor shell and two 16-foot doors.
A 3 car garage cost calculator is only as good as the unit prices behind it. Plugging in a national average labor rate will miss regional swings. In high-cost metros, labor and permit fees can push the total 30% or more above the same plan in a rural county. For a line-item takeoff that reflects your market, see garage estimating services.
Understanding these drivers helps you compare bids apples to apples. When one bid is $20,000 lower, it usually means a lever was set differently—thinner slab, fewer doors, or no insulation.
Before you compare bids, write down the five levers and confirm each bidder used the same assumptions on footprint, foundation, wall height, doors, and finish.
3 Car Garage Cost by Size: Typical U.S. Ranges
The table below shows common 3 car garage footprints and typical cost ranges for a basic, unfinished detached garage. These are U.S. ranges and vary by region, scope, and date.
| Footprint | Square Feet | Typical Cost Range | Cost per Square Foot |
|---|---|---|---|
| 24x30 | 720 | $45,000–$65,000 | $63–$90 |
| 30x30 | 900 | $55,000–$80,000 | $61–$89 |
| 32x40 | 1,280 | $70,000–$105,000 | $55–$82 |
| 36x40 | 1,440 | $78,000–$120,000 | $54–$83 |
Square footage is the primary cost driver but not linear—larger garages have lower per-square-foot costs because fixed costs (permits, equipment, mobilization) spread over more area. A 3 car garage is usually 600–1,200 square feet; tandem layouts (two deep, one wide) change the framing and door count, often adding wall length without adding door openings.
These ranges are for basic unfinished garages. Adding HVAC, insulation, drywall, and paint pushes the number toward the top or beyond. For a size-specific 3 car garage building cost, run a takeoff on your actual plan rather than scaling from a table. A residential estimating services team can build that takeoff from your drawings.
Tandem layouts can reduce door count but increase wall and roof area—always price the actual geometry, not just the car count.
3 Car Garage Cost Breakdown by CSI MasterFormat Division
A 3 car garage cost breakdown by CSI MasterFormat division shows where the money goes and helps you spot when a bid is low because a scope item is missing. The major divisions for a basic detached garage are Division 03 Concrete (slab, footings), Division 06 Wood, Plastics & Composites (framing), Division 07 Thermal & Moisture Protection (roofing, siding, waterproofing), Division 08 Openings (garage doors, windows, man doors), Division 09 Finishes (drywall, paint), and Division 26 Electrical.
Typical percentage ranges as a share of total cost: concrete 10–15%, framing 15–20%, roofing 8–12%, siding 5–8%, doors 10–15%, electrical 3–5%, and finishes 0–10% depending on whether the space is finished. These ranges shift with region and design, but they give you a sanity check on any bid.
Plumbing and HVAC are often excluded from basic garages but appear when the space is conditioned or includes a workshop sink. Insulation may fall under Division 07 or Division 09 depending on how your estimator categorizes it. A professional quantity takeoff services maps directly to these divisions, so every line item has a quantity, unit, and cost code.
When a bid comes in 20% under the pack, check Division 03 and Division 08 first. A missing vapor barrier, undersized footings, or single-skin garage doors are common omissions that show up later as change orders. A division-level breakdown makes those gaps visible before you sign.
Ask each bidder to submit their price broken out by CSI division. If they cannot, you cannot compare scope—only totals.
3 Car Garage Cost Formula and Calculator Inputs
A 3 car garage cost formula gives you a defensible starting number before you commit to a bid. Use this structure:
Total Cost = (Area × Cost per Square Foot) + Sitework + Utility Connections + Permits + Contingency
Area is the slab footprint in square feet, not the driveway or apron. Cost per square foot is your local all-in rate for the shell and basic finishes. Sitework, utility connections, permits, and contingency are added as separate line items because they vary too much to bury in a unit rate.
A 3 car garage cost calculator needs these inputs to produce anything useful:
- Length and width. A 3 car garage is typically 30 to 36 feet wide and 20 to 24 feet deep, giving 600 to 864 square feet. Enter the actual plan dimensions, not a rounded guess.
- Wall height. Standard is 8 to 10 feet. Each additional foot of wall height adds framing, siding, and sometimes a taller door opening.
- Roof pitch and type. A 4/12 gable is the common minimum for shingles. Steeper pitches and hips add framing and roofing squares.
- Garage door size and count. Two 9x8 doors plus one 16x8 door is a common three-car layout. Door cost scales with width, insulation, and window options.
- Foundation type. Slab-on-grade, stem wall, or full perimeter footing with frost depth. Foundation type is the largest single variable after sitework.
- Siding material. Vinyl, hardboard, fiber cement, stucco, or brick veneer. Each carries a different material and labor rate.
- Finish level. Unfinished interior with exposed studs is cheapest. Insulated, drywalled, painted, and heated is a different building.
Treat the 3 car garage cost formula as a conceptual estimate, not a bid. It ignores soil bearing capacity, slope, rock excavation, utility trench length, code-driven fire separation, and regional labor rates. Those items can swing the total by 20% or more in either direction.
Adjust the formula for attached versus detached construction. An attached garage shares the house foundation, roof plane, and electrical service, so you remove those standalone costs but add fire separation and weatherproofing details. A detached garage carries its own foundation, roof, siding, and often a separate electrical feed, which pushes the unit rate up.
Adjust for heated versus unheated space. A heated garage needs insulation, a vapor barrier, a heat source, and often a higher electrical load. Add those as line items rather than increasing the square foot rate, so you can see what the comfort upgrade actually costs.
Finally, add a waste factor to every material quantity before you price it. Framing lumber typically runs 5–10% waste, while siding and roofing typically run 10% because of cuts, laps, and breakage. A material takeoff service applies these factors line by line so your material dollars match what the crew will actually install. If you skip waste, your labor and materials budget will be short before the first delivery. When you present the final number to a client, it helps to show how the cost to build 3 car garage breaks down by division, so they see where the 3 car garage price comes from and can compare it against other bids.
A calculator that only multiplies square footage by a rate will understate your cost on any site with slope, rock, or a long utility run. Add those items as separate lines.
Worked Example: 3 Car Garage Cost Estimate for a 30x30 Detached Garage
Example only. The numbers below are illustrative and will not match your project. They show the method, not a quote.
Assume a 30 ft × 30 ft detached garage, 900 sq ft, 10 ft walls, gable roof, two 9x8 doors and one 16x8 door, unfinished interior, slab-on-grade. Here is the math:
- Concrete slab and footings: 900 sq ft × $8/sq ft = $7,200
- Framing: 900 sq ft × $12/sq ft = $10,800
- Roofing: 1,100 sq ft (with overhangs) × $5/sq ft = $5,500
- Siding: 1,200 sq ft × $6/sq ft = $7,200
- Garage doors: 3 doors × $1,500 = $4,500
- Electrical: $2,500
- Permits: $1,200
Sum: $7,200 + $10,800 + $5,500 + $7,200 + $4,500 + $2,500 + $1,200 = $38,900
Add 10% contingency: $38,900 × 0.10 = $3,890
Total: $38,900 + $3,890 = $42,790
This excludes sitework, driveway, and utility trenching. On a flat lot with a short utility run, those items might add $5,000 to $15,000. On a sloped lot with rock, they can exceed the building shell cost.
This is a conceptual 3 car garage estimate. A bid-ready estimate would break each line into labor, material, and equipment. For example, the concrete line becomes formwork, rebar, concrete, pump, finish, and curing, each with its own quantity and unit cost. The framing line becomes plates, studs, headers, trusses, sheathing, and hardware, priced by piece count and board feet.
A 3 car garage cost estimator working from a takeoff will also separate waste, sales tax, and subcontractor markup. That level of detail is what turns a square-foot guess into a number you can bid. If you want that breakdown without doing every count yourself, a concrete takeoff and a framing takeoff give you the quantities to price. A full quantity takeoff is the backbone of any construction estimating and estimating workflow that needs to survive a bid review.
Always add contingency as a separate line. If you bury it in the unit rates, you cannot see how much risk you have priced.
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Attached vs. Detached: How 3 Car Garage Construction Cost Changes
An attached garage shares its foundation, roof plane, and utility service with the house. That sharing usually lowers the cost per square foot because you are not buying a second roof, a second service lateral, or a standalone foundation system. It also complicates the framing where the garage roof meets the house roof, and it demands careful flashing and weatherproofing at every intersection. Those details cost labor even when the materials are minimal.
A detached garage stands on its own. It needs a separate foundation, roof, siding envelope, electrical service, and often its own driveway approach and apron. The 3 car garage construction cost for a detached unit is therefore higher per square foot at the same finish level, because nothing is shared except the site.
Attached garages usually must match the house foundation type, whether that is a basement wall, crawl space stem wall, or slab. Detached garages are more flexible and are commonly built slab-on-grade or on a stem wall with a slab. That flexibility can save money if the house foundation is expensive, but it also means the garage floor may sit at a different elevation than the house floor.
Fire separation is a code issue that hits attached garages. Under the IRC and IBC, the wall and ceiling between an attached garage and the living space typically require a fire-rated assembly, often 1/2-inch or 5/8-inch gypsum board, and the door between garage and house usually must be fire-rated and self-closing. Detached garages generally do not trigger those requirements because there is no shared wall.
As a rough rule, a detached garage costs 10–20% more per square foot than an attached garage at the same finish level. That range shifts with site conditions, utility distance, and whether the detached unit needs its own heat and insulation. When you price either option, start with a foundation estimate that reflects the actual soil and frost depth, then build the framing, roofing, and envelope lines on top of it.
The 10–20% detached premium is a planning rule, not a bid. Confirm it with a takeoff once you know the foundation type and utility run.
Sitework, Excavation, and Foundation Costs
Sitework for a 3-car garage starts with clearing and grubbing the footprint, then excavation to subgrade. You backfill around footings in lifts, compact to 95% Standard Proctor, and fine grade the pad. Utility trenching for power, water, and gas runs from the house or street, and a detached garage often needs a separate trench. On a level lot with good access, these scopes are a small share of the budget. On a sloped or wooded lot, they can rival the shell package.
The concrete slab is typically 4–6 inches thick over a 6-mil vapor barrier and welded wire mesh or #4 rebar at 18–24 inches on center. Perimeter footings and any interior bearing piers must bear below the local frost depth, which ranges from a few inches in the South to 48 inches or more in northern states. Division 03 concrete covers the footings, stem wall, slab, and any apron. A 30x30 slab at 5 inches thick is about 14 cubic yards of concrete before waste, so thickness changes move the number fast.
Poor soil or a high water table changes the foundation scope. You may need engineered fill, helical or concrete piers, a thickened slab edge, or a fully suspended structural slab. Each of those adds design, inspection, and material cost. If you are pricing these scopes, excavation and earthwork estimating and foundation estimating separate the dirt work from the concrete so you can see which one is driving the number.
Driveway and apron costs are usually excluded from a garage estimate, but they are significant. A concrete driveway at 4–6 inches thick over compacted base can run thousands of dollars for a 3-car approach, and asphalt is cheaper up front but needs more maintenance. Ask whether the quote includes the apron, the driveway, and any curb or drainage improvements. If not, add them as a separate line.
Confirm frost depth and soil bearing capacity before you price the foundation. A slab on grade that works in one county may need piers two counties north.
Framing, Roofing, and Siding: The Shell Package
Framing covers the walls, trusses or rafters, sheathing, and connections. Wall height matters: a 10-foot wall uses more studs, plates, and sheathing than an 8-foot wall, and it changes the door header and the roof line. Roof pitch and overhangs change the roof area, so a 6:12 pitch over a 30x30 footprint is not 900 square feet of roofing. The plan view is 900 square feet, but the sloped area is larger, and overhangs add more. Trusses are usually cheaper than site-built rafters for a simple gable, but a hip or complex roof shifts labor and material.
Roofing includes underlayment, shingles or metal panels, flashing, drip edge, and gutters. Asphalt shingles are the common baseline, while standing seam metal costs more per square but lasts longer. Ice and water shield is required in many cold-climate code jurisdictions along eaves and valleys. Gutters and downspouts are often a separate line, and they need to discharge away from the slab. If the garage is detached, the roof may need its own drainage plan.
Siding options include vinyl, fiber cement, stucco, and metal. Vinyl is the lowest material cost and the fastest to install, but it can look thin on a large wall. Fiber cement holds paint well and takes a lap or panel profile, at a higher material and labor cost. Stucco needs a substrate, lath, scratch, and brown coat, and it is common in the Southwest. Metal siding pairs well with a metal roof and a shop or agricultural look.
Waste factor is where estimates drift. For framing lumber, plan on 5–10% waste. For siding, 10% is typical, and for roofing, 10–15% covers cuts, hips, valleys, and starter courses. Labor is the other half of the shell package, and it tracks local wage rates and crew productivity. If you want the shell priced line by line, framing estimating, roofing estimating, and siding estimating break out materials, waste, and labor so the bid is defensible.
Roof area is not footprint area. Multiply the footprint by the pitch factor before you order shingles, or you will run short on a steep roof.
Garage Doors, Electrical, and MEP Rough-In
Garage doors are a major line item in any 3-car garage. You can frame one 16-foot double door plus one 8-foot single, or three 8-foot singles, or three 9-foot singles. Insulated doors cost more than non-insulated and help if the garage is attached or conditioned. Openers, keypads, and safety sensors are separate. Door height matters too: an 8-foot door needs a taller wall and header than a 7-foot door, and that changes the framing. Division 08 openings covers doors, hardware, and glazing, and it is often the largest single line after concrete. Because door size and count drive both material and labor, they are a key driver of the cost to build 3 car garage, and they can shift the 3 car garage price by thousands depending on the configuration you choose.
Electrical includes lighting, outlets, garage door openers, and a subpanel if the garage is detached. The NEC governs GFCI protection for receptacles in garages and dedicated circuits for large tools, welders, or EV chargers. A 3-car garage may need a 60-amp or 100-amp subpanel fed from the house, plus conduit and conductors in a trench. Lighting is usually LED shop fixtures, and you should plan for switched circuits and enough outlets along the walls and ceiling. Division 26 electrical covers this scope, and it is easy to underestimate the trench and feeder cost on a detached build.
Plumbing and HVAC are optional but common if the garage includes a workshop, laundry, or living space above. A slop sink, hose bib, or laundry rough-in adds piping and venting under Division 22. Heating and cooling can be a ductless mini-split, a unit heater, or a full duct system if there is a second floor. Division 23 covers HVAC, and the load calculation changes if the space is conditioned. Insulation and drywall are often added for comfort and code compliance, especially when the garage is attached or the wall is shared with living space. Division 09 covers drywall, tape, texture, and paint.
These scopes are where a 3-car garage cost estimate either holds or falls apart. A door schedule, a lighting plan, and a mechanical narrative give you something to price. Without them, you are guessing at counts. If you need the openings and electrical priced from the drawings, openings estimating and electrical estimating turn the plans into counts and lengths you can bid.
Decide door sizes and opener locations before framing. Moving a header or adding a subpanel feed after the walls are up costs far more than pricing it now.
Permits, Codes, and Inspections
Permit fees for a 3 car garage vary widely by jurisdiction and are often based on square footage or the declared construction valuation. Some cities charge a flat fee, others use a sliding scale tied to the total value of the work, and many add separate charges for electrical, plumbing, and mechanical permits. Always include a permit line in your 3 car garage estimate rather than treating it as a post-award surprise, and confirm the current fee schedule with the local building department before you finalize your number.
The IRC and IBC set minimum requirements for foundations, framing, egress, and fire separation. For a detached garage, the IRC is commonly the governing residential code, while the IBC applies to larger or mixed-use structures. Fire separation matters most when the garage is attached: a wall or ceiling assembly with a specified fire-resistance rating is typically required between the garage and the living space, and that assembly changes your drywall, insulation, and door schedule.
The NEC governs electrical work, including GFCI protection for receptacles, dedicated circuits for garage door openers, and lighting requirements. If you add a slop sink, laundry, or bathroom, the IPC or UPC governs the plumbing rough-in, venting, and fixture connections. Inspections add time to the schedule and may require revisions if work is not to code, so budget for at least one framing, one electrical, and one final inspection. A budget estimating service can help you carry allowances for permits and code-driven scope before the drawings are final.
Permit fees and code requirements are jurisdiction-specific. Verify the fee schedule and the adopted code edition with your local building department before you lock your estimate.
Common Mistakes in 3 Car Garage Cost Estimating
- Leaving sitework, driveway, and utility connections out of the number. A 3 car garage cost that stops at the slab misses excavation, backfill, grading, the driveway apron, and the trenching for power and water. These items can move the total by thousands of dollars, so carry them as separate line items.
- Borrowing a cost per square foot from a different region or finish level. A number from a low-cost market with vinyl siding will not price a high-cost market with masonry veneer and insulated doors. Rebuild the estimate from quantities and local unit costs instead of scaling someone else's square foot figure.
- Underestimating the waste factor for framing and siding. Lumber, sheathing, and siding are ordered with waste, and complex roof geometry or a gable end with multiple openings increases it. Use a realistic waste factor per material rather than a single blanket percentage across the whole shell.
- Ignoring code requirements for fire separation, GFCI, and egress. These items are easy to omit in construction estimating because they are not visible on a simple floor plan, but they drive real material and labor. Missing them means your bid is short before you ever break ground.
- Not accounting for overhead and profit in a contractor bid. A 3 car garage cost for contractors must carry general conditions, overhead, and profit on top of direct costs. Pricing only labor, material, and equipment leaves nothing to run the job or absorb risk.
Run a second-opinion review on your takeoff before you submit. An [estimate review service](/estimate-review-services/) can catch missing scope and math errors while there is still time to adjust.
3 Car Garage Cost for Contractors: Bidding and Takeoff
Contractors need a detailed takeoff to price labor, material, and equipment accurately. A square foot number is fine for a homeowner's budget, but a bid requires quantities: cubic yards of concrete, board feet of lumber, squares of roofing, linear feet of siding, and each door, window, and light fixture counted. That quantity takeoff becomes the backbone of the estimate, and every line should tie back to a drawing or specification.
A 3 car garage cost for contractors must include overhead and profit, typically 10–20% depending on the market, project size, and risk. Direct costs cover labor, material, equipment, and subcontractors; above that you carry general conditions, insurance, bonding, and margin. If you are bidding to a general contractor, confirm whether your number is expected to include sales tax, permits, and cleanup, because assumptions vary by trade and region.
Bid-ready estimates break down by CSI MasterFormat division and include quantities with waste factor. That structure lets a reviewer compare your number to another bid line by line and shows the owner exactly what is and is not included. A 3 car garage cost estimator tool can speed up the takeoff, but it must be calibrated to local labor rates and material pricing or the output will be misleading. Many contractors outsource the takeoff to a specialized service to cut bid time and improve accuracy, especially during a busy bid calendar. If you are a general contractor, general contractor estimating support can carry the full division structure; trade contractors can use subcontractor estimating services for a scoped package.
Same-day quotes are available, and most takeoffs are bid-ready in 48 hours. Rush turnaround is available when a bid date is close.
When to Get a Professional 3 Car Garage Estimate
A professional 3 car garage estimate becomes necessary when you need a bid-ready number for financing, permits, or a fixed-price contract. Lenders and building departments expect documented quantities and costs, not a ballpark figure. If you are signing a contract that locks your price, an accurate 3 car garage cost estimator protects you from overpaying or underbidding.
When the garage is part of a larger project — a new house, an ADU, or a shop — scopes overlap. Excavation, concrete, framing, and MEP runs share labor and materials with the main structure. A standalone garage estimate that ignores those overlaps will miss savings or double-count costs. Professional construction estimating ties the garage scope to the rest of the project so nothing falls through the cracks.
Comparing contractor bids is another trigger. Bids that look apples-to-apples often hide different assumptions: one includes the slab and footings, another excludes them; one lists overhead and profit separately, another buries it in unit prices. A third-party quantity takeoff gives you the same line items and units for every bidder, so you can see who is actually cheaper. It also gives you leverage in negotiation because you know the real quantities.
You can get a same-day quote from Scope Precision Estimate by uploading your plans. A full construction cost estimating package is bid-ready in 48 hours, and new clients get 20% off. For garage-specific scope, see our garage estimating services.
If your bid deadline is tight, ask about rush turnaround — most garage estimates are delivered in 24–48 hours.
Frequently asked questions
How much does it cost to build a 3-car garage per square foot?
Most U.S. projects land between $45 and $90 per square foot for a detached 3-car garage, with attached garages often at $35 to $70 per square foot because they share the house foundation, roof, and utility runs. The low end assumes a simple rectangular plan, asphalt driveway, and standard 8-foot doors. The high end reflects brick or stone veneer, architectural shingles, insulated doors, HVAC, and upgraded electrical. Region, soil conditions, and finish level move the number more than size does, so always price your own plan rather than applying a single rate.
Is it cheaper to build an attached or detached 3-car garage?
Attached is usually cheaper per square foot. It shares the house foundation system, roof plane, exterior wall finishes, and utility runs, and it may not need its own heating source. Detached garages carry their own footing and slab, full four-wall envelope, separate roof, and often a new electrical service or subpanel feed. Detached also adds driveway, apron, and sometimes a second meter. The gap typically runs $8 to $20 per square foot, though a detached garage on flat ground near existing utilities can close much of that difference.
Do I need a permit to build a 3-car garage?
Yes, in nearly every U.S. jurisdiction. You will typically need a building permit, plus separate electrical, plumbing, and mechanical permits if you run power, water, or HVAC to the structure. Detached garages over a certain size, often 200 to 400 square feet, almost always require a permit, and many HOAs add design review on top. Expect plan review fees, zoning setback checks, and inspections at footing, slab, framing, electrical rough-in, and final. Budget permit and review costs as a line item rather than an afterthought.
How long does it take to build a 3-car garage?
A detached 3-car garage typically takes 8 to 16 weeks from permit issuance to final inspection. Sitework and foundation run 1 to 2 weeks, framing and drying-in 2 to 4 weeks, and MEP rough-in, insulation, drywall, and trim another 3 to 6 weeks. Weather, inspection backlogs, and door lead times are the usual delays. Attached garages can take longer because they tie into the existing house structure and may require re-roofing and siding transitions. Permit review alone can add 2 to 8 weeks before any work starts.
What is the average size of a 3-car garage?
Most 3-car garages fall between 720 and 1,000 square feet. A common layout is 30 to 32 feet wide by 24 feet deep, giving roughly 720 to 768 square feet with three 9-foot doors. Adding a workshop bay, storage depth, or a third bay set perpendicular pushes the footprint to 900 to 1,200 square feet. Depth matters more than width for truck and SUV clearance, so verify door width, interior column spacing, and turning radius before locking the plan.
Can I build a 3-car garage for under $30,000?
It is possible in lower-cost regions with a basic detached plan, but it is tight. A 720 sq ft garage at $40 per square foot is $28,800, which assumes a simple slab, wood frame, asphalt driveway, three standard doors, and minimal electrical. Any of these pushes you over: brick or stone veneer, insulated doors, HVAC, a long driveway, poor soils, or utility extensions. Get a real takeoff before committing. A construction takeoff service can confirm quantities and expose the line items that break the budget.
How much does a 3-car garage slab cost?
A 4-inch reinforced slab on grade for a 3-car garage typically runs $6 to $12 per square foot, so a 900 sq ft slab lands near $5,400 to $10,800. That range covers gravel base, vapor barrier, welded wire mesh or rebar, formwork, and finishing. Add $2 to $5 per square foot for thickened footings, a turned-down edge, or a post-tension design. Slopes, poor soils, or a frost-protected shallow foundation push it higher. The slab is one of the few items you should never value-engineer.
What is the difference between a 3-car garage and a 2-car garage cost?
The main difference is the third bay footprint, one extra overhead door, and roughly 200 to 300 additional square feet of slab, wall, and roof. A 2-car garage at 400 to 500 sq ft commonly runs $18,000 to $40,000, while a 3-car at 720 to 900 sq ft runs $32,000 to $81,000. The third bay adds a door, more framing, more roofing, and often a wider driveway apron. Per-square-foot cost is similar, but the absolute number climbs fast because every trade scales with the footprint.