Garage construction: what to know

What the job involves, what changes the price, and what to ask a pro.

What garage construction is

Garage construction builds a detached or attached garage with a slab, framing, a roof, siding, a garage door and electrical service. People add a garage when they need covered parking, workshop space or secure storage, and the project has to follow the plans, the local code and the setback rules for the lot.

Signs you need it

  • You park outside and need covered, secure space for vehicles, tools or equipment
  • Your current garage is too small for the vehicles you own, or the door no longer opens reliably
  • You want a workshop with power, lighting and a bench, and you need the building to meet the code for that use
  • A detached garage would add useful space without changing the footprint of the main house
  • Your lot has room for a new building, and you need someone to confirm the setbacks and the permit requirements first

What the pro does

  • The builder checks the lot for setbacks, easements and the location of utilities before any ground is broken
  • They excavate, set forms and pour the slab with reinforcement, and check the slab for level and drainage
  • They frame the walls, the header over the door opening and the roof trusses or rafters, and anchor the frame to the slab
  • They install the roof sheathing, underlayment and shingles or metal roofing, then the siding and the trim
  • An electrician runs the service, the outlets, the lights and the garage door circuit, and each is inspected
  • They hang the garage door and the opener, adjust the tracks and check the safety reverse before handing over the building

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Size and door count, since a two-car garage with a wide door needs a heavier header and more framing
  • Attached versus detached construction, which changes the tie-in to the house roof and foundation
  • Slab work, including excavation, base prep, reinforcement and any thickened edges for the door
  • Electrical scope, such as outlets, a subpanel, heating or a large workshop load
  • Roof pitch, the roofing material and whether the garage will carry a second floor or storage loft
  • Garage door type and the opener, including insulated doors and smart openers
  • Site access, grading and whether soil must be removed or brought in

What a written quote should spell out

  • Slab dimensions, thickness, reinforcement and whether a vapor barrier is included
  • Framing lumber grade and wall height, with the header size over each door opening
  • Roof material, underlayment and the gutter and downspout scope
  • Electrical work listed by circuit, outlet and light, with the panel tie-in shown separately
  • Garage door model, opener type, and whether the install includes the tracks and safety sensors
  • Permit and inspection responsibility, and the inspection stages the work must pass

Questions to ask before you hire

  • Does the design meet the setback rules for this lot, and who confirms them before the slab is poured?
  • What slab thickness and reinforcement will you pour, and will the slab be sloped away from the building?
  • Who is pulling the permit, and at which inspection stages will the work be checked?
  • Will the garage door header and the framing be sized for the door width and the roof load?
  • Who runs the electrical work, and is the panel able to take the new circuits?
  • How will the attached roof tie into my existing roof without leaks?
  • What warranty do you give on the slab, the roof and the garage door installation?

Red flags

  • They pour a slab without checking the setbacks or the location of buried utilities
  • They frame the door opening without a properly sized header for the span
  • They cannot tell you who does the electrical work or whether the inspection is booked
  • They want the full payment before the slab, framing or roof has passed inspection

What you can do yourself

You can clear the site, mark the building footprint, gather the survey and the plan, and choose the door and windows. Do not pour the slab, frame the walls or set the roof yourself, because the structure depends on correct sizing and anchoring. Electrical work should go to a licensed electrician where required, and the garage door install to a trained installer, since a door under spring tension or a live circuit can cause serious injury.

Licenses and permits

A garage is commonly built under a building permit, and the electrical work must be done by a licensed electrician in most places. The general contractor may need a license or registration. Check with your state or local licensing agency and your local building department for the permit, setback and trade rules that apply to your lot.

Garage construction questions

Do I need a permit for a detached garage?

Many places require a permit for a new garage, even when it is a simple building. Ask the local building department before you order materials, and ask what inspections the job requires.

How close to the property line can a garage be?

That depends on the local setback rules, which often differ for the side, rear and front of the lot. Ask the local zoning office for the setbacks for your lot before the design is finished.

Can I add a workshop with power to the garage?

Yes, but the electrical service must be sized for the tools you plan to run. Tell the electrician the tools and the heating you plan to use so they can size the circuits and the panel.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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