A new detached garage is a building on your lot, not a furniture order and not a garage conversion.
Homeowners mix those up. Conversion and ADU work turn existing space into living area. This page is about building a separate structure for vehicles or storage. Cities disagree on when a "small" accessory building needs a permit, whether a garage always needs one, and what the foundation can look like. A detached garage building permit is the local approval for that new structure — zoning first for where it may sit, then building plans for how it is built. PermitCove is an independent homeowner guide, not your building department. See our disclaimer.
Related: garage conversion and ADU permits · carport permits · shed permit requirements · driveway and curb-cut permits · zoning variance and setbacks · how to apply for a building permit.
Garage, shed, or living space?
Portland's accessory-structure page is explicit: its garage and shed path is for buildings that are not heated and not used for living. Habitable structures need a building permit regardless of size. If you plan bedrooms, a kitchen, or an ADU in the new building, stop and use the living-space or ADU process instead. Our garage conversion and ADU guide is that lane. Calling a studio a "garage" on the application does not make it one. Going the other way, if all you want is a roof over the cars with at least two sides left open, that is usually reviewed as a carport; see carport permits.
City of Lakewood, Colorado, publishes a residential detached garage handout for single-family lots. A permit is required for all garages regardless of size. Homeowners may obtain the building permit for a detached garage or accessory building on their own primary residence if they perform the work themselves. Anyone hired must have the required city registration. Mechanical, electrical, and plumbing work needs registered trades (or the homeowner added to the permit for those systems). That is Lakewood's rule, not a national owner-builder right.
Virginia Beach lists carports and garages (attached or detached) among residential projects that need building permits, and it lists inspections for garages and sheds over 256 square feet. Detached structures such as sheds greater than 256 square feet are called out separately on the same page. Do not treat 256 as a free pass for a garage in another city.
A shed exemption is not a garage exemption. Read the line your city actually wrote.
Size and height triggers for a new garage
Portland requires a building permit to build, tear down, or change a non-heated, non-habitable accessory structure that is over 200 square feet (interior of exterior walls) and/or taller than 15 feet. Structures 200 square feet or smaller may skip the building permit but can still need a zoning permit. On lots over two acres, Portland also describes a path with no building permit if the structure is under 400 square feet and at least 20 feet from property lines and other structures — still confirm zoning.
Chandler's April 2026 homeowner manual exempts one-story detached accessory structures when floor area does not exceed 120 square feet and height does not exceed seven feet. That is an accessory exemption, not a blank check for a two-car garage. Chandler's zoning for accessory buildings (guest quarters, garages, workshops) also puts them behind the front wall plane, limits rear-yard coverage, caps height at fifteen feet in that section, and generally allows a maximum of one such accessory building on a lot. Talk to planning before you assume a second structure is fine.
Lakewood's garage handout does not offer a size exemption for garages. If your city copied the International Residential Code accessory exemption for small sheds, ask whether garages are carved out. Many homeowners lose money by building a "shed" that is obviously a garage.
Size, height, heat, foundation, and the driveway each change what you submit.
Zoning and driveway before you order trusses
Portland tells applicants to call zoning staff for setbacks and to use the Detached Covered Accessory Structure Worksheet. The Zoning Code limits size, placement, coverage, and setbacks. Building a garage also requires driveway access; if you do not have a driveway, you must put one in. Driveways within 150 feet of an improved public right-of-way must be paved under the rules Portland cites, and work in the right-of-way needs a separate transportation permit. That is the same family of problems as our driveway and curb-cut guide. The building permit for the garage walls does not automatically include the apron in the street.
Lakewood tells applicants to verify setbacks with the Planner-of-the-Day before they rely on the plot plan. Snohomish County's January 2025 Assistance Bulletin #26 (unincorporated county only) adds another scale: private garages and storage buildings generally need a building permit and stormwater pollution prevention plan approval, and footprints over 2,400 square feet can need conditional use review with larger side and rear setbacks. Lighting must be hooded so it does not glare onto neighbors. Large buildings may need screening. Those are county rules for that jurisdiction, not a template for your suburb.
If the setback is wrong, a variance is a different application. See the zoning variance guide. Perfect framing plans on the wrong spot still fail.
Building close to the house: the 3-foot rule
On a narrow lot the garage often ends up a few feet from the house, and that distance matters even though the two buildings never touch. The model residential code’s garage separation table (Table R302.6) has a line for “garages located less than 3 feet from a dwelling unit on the same lot.” For those, it calls for at least 1/2-inch gypsum board or equivalent on the interior side of the garage’s exterior walls within that area. Walls that run perpendicular to the house wall are not covered by that requirement.
Lewiston, Maine prints the table in its residential garage tip sheet (Lewiston garage separation tip sheet), and Minnesota’s adopted rule carries the same line (Minn. R. 1309.0302). Put the garage 3 feet or more away and that line of the table no longer applies to it.
Two practical notes. Show the measured distance from the garage to the house on your plot plan, because the reviewer will look for it. And if you are tempted to leave the inside unfinished, check that distance first; a garage 2 feet from the house may need drywall on that wall even if the rest stays bare studs. Your city may have amended the table, so confirm the version it uses.
Foundations, heat, and trades
Lakewood's handout is unusually clear on foundations. Monolithic slab foundations are restricted to unheated buildings of light frame construction with a maximum of 600 square feet and a 10-foot wall height. Heated detached garages must be insulated to the International Energy Conservation Code path the city applies, with window and door U-values and R-values listed for walls, ceiling, and slab or foundation. Factory-built trusses need shop drawings sealed by a registered Colorado professional engineer. A soils report is required for detached garages over 600 square feet or closer than 10 feet to the primary structure. Indicate whether the garage will be heated, plumbed, or wired; include gas or plumbing schematics if applicable; show lights, switches, outlets, and the power source; and if a subpanel is installed, provide a single-line diagram. The service or subpanel directory must identify spaces reserved for future EV charging as "EV CAPABLE."
Portland folds electrical, plumbing, and mechanical into optional residential combination permits with the building permit, or you pull trade permits separately. Subcontractors must be registered with the State of Oregon. Steep sites (over 20 percent slope) need a geotechnical report from an Oregon-registered engineer. Ground disturbance needs erosion control. Adding more than 1,000 square feet of impervious area needs a stormwater plan on the site plan. Lots 5,000 square feet or greater must follow tree preservation standards.
Spend your drawing time on the plot plan and the foundation detail.
Garage planning checklist
- Confirm you are building a non-habitable garage or storage building — not an ADU or finished living space.
- Ask planning for setbacks, height, lot coverage, and how many accessory buildings your lot allows.
- Ask building whether your size and height need a building permit, a zoning-only permit, or both.
- Decide heated vs unheated before you pick a slab detail.
- Draw a plot plan with the house, the proposed garage, and dimensions to property lines and other structures.
- Plan driveway access and any right-of-way work as its own permit question.
- List electrical, gas, and plumbing scopes; register trades if your city requires it.
- If factory trusses or a soils report are required at your size or distance, budget them before you submit.
- Use the how to apply guide for the general application sequence, then follow your city's garage handout for the drawings.
Mistakes that stall garage permits
- Using a shed square-footage exemption that does not apply to garages (Lakewood requires a permit for all garages).
- Pouring the pad in a setback because "the neighbor's garage is closer."
- Filing a garage permit while planning a bedroom and bath inside.
- Ignoring driveway and curb-cut permits until the inspector asks where the cars enter.
- Choosing a monolithic slab for a heated garage the handout does not allow.
- Hiring unregistered contractors where the city requires registration on the permit.
Settle where it sits and what it stands on before anything is ordered.
Last checked: October 31, 2026.
Official sources
- City of Portland — Garages, sheds, and accessory structures
- City of Lakewood, CO — Residential Detached Garage handout
- City of Virginia Beach — Residential Building Permits
- Snohomish County — Assistance Bulletin #26, Residential Garages and Storage Buildings (Rev. January 2025)
- City of Chandler — Home Owners Building Permit Manual (April 2026)
- City of Lewiston, ME: Construction Tip Sheet, Residential Garage Separation (Table R302.6)
- Minnesota Rules 1309.0302: IRC Section R302 as adopted, including Table R302.6
Before you order concrete
A new detached garage is a zoning location problem and a building construction problem. Portland's 200-square-foot and 15-foot triggers, Chandler's 120-square-foot accessory exemption, and Lakewood's "all garages need a permit" rule are local sentences. Heated vs unheated changes the foundation and energy packet. Driveway work can be a separate permit. Confirm setbacks and the drawing list with your city before you order concrete.
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