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Need More Parking? Here’s the Average Cost of a Garage Extension

At HomeLight, our vision is a world where every real estate transaction is simple, certain, and satisfying. Therefore, we promote strict editorial integrity in each of our posts.

In light of the COVID-19 pandemic, many homeowners feel the urge to expand and enhance their living space. Maybe you need more space now that your kids moved back home, or perhaps you need a designated home office to get away from household distractions. Whatever the reason, you’re considering expanding your garage for some additional square footage.

On average, the cost to expand a garage runs between $16,749 and $38,930. To help you figure out the specifics, HomeLight researched all of the finer points of getting the job done and spoke with two expert contractors who have decades of experience expanding garages.

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Garage expansion cost overview

The average cost to expand a garage ranges since many variables influence project cost. As Pete Baughman, owner and developer of the Seattle contracting firm Better Builders, puts it, “It’s tricky. I like to use the analogy with my homeowners: ‘How much does it cost to buy a white car?’ It’s a hard question to answer without a larger plan.”

Still, we can estimate average cost ranges according to project costs homeowners and contractors report to the following reputable remodeling websites. The data below is primarily based on the cost to roughly double the size of your existing garage:

Source: HomeAdvisor

Average garage expansion cost: $16,749-$38,930

Average cost per square foot: $40-$70

Small extension: $10,500-$27,000

Large extension: $57,000+

Methodology: HomeAdvisor connects people with pros for home projects and has both parties fill out a short survey after completing the job. The above data reflects those survey responses.

Source: HomeGuide

Average garage expansion cost: $23,900

Average cost per square foot: $49

Small extension: $10,800

Large extension: $42,700+

Methodology: The site uses software to track millions of estimates from contracting companies and releases reports on average costs for their website’s home improvement cost calculator.

Source: Thumbtack

Average garage expansion cost: $4,500 – $80,000

Average cost per square foot: $30 – $40

Standard garage addition (26 x 40 feet): $38,000

Upscale garage addition (40 x 80 feet): $80,000

Methodology: Thumbtack receives requests from users for estimates from contractors and routes them to professionals for a quote. The company then crunches data from millions (more than 1 million so far in 2021 alone) of quotes to release accurate reports on estimated prices.

If you’re just looking to add a couple of feet to your garage, construction cost range from about $2,000 to $12,000.

Get to know the materials when figuring out the cost to expand garage
Source: (romakoma / ShutterStock)

These factors have the most significant impact on the final price

Now that we’ve covered the average project cost range, let’s dive into the details of factors that impact your cost.

The complexity of construction

If your garage extension site is on sloped land or offset from your home’s pre-existing frame, you may need to hire a structural engineer to troubleshoot. Gerry Holzapple Jr., partner of Holzapple Construction in Vacaville, CA, shares: “Most contractors aren’t engineers, but if owners want construction that is counter to standard building practices, then an engineer has to be involved.”

Holzapple also tells us that the going rate for a structural engineer is about $150 per hour. HomeAdvisor reports that the average engineering plan costs anywhere from $800 to $3,000, or as much as 20% of the overall construction price.

Construction materials

The materials you build greatly influence the final price. Notice how cost ranges for the following components depending on the chosen materials (all figures reflect price per square foot):

  • Siding: $0.80 to $50
    • Aluminum: $1.50-$7
    • Brick: $5-$15
    • Hardie Board: $0.80-$5
    • Natural Stone: $28-$50
  • Flooring: $0.15-$25
    • Laminate flooring: $2-$5
    • Vinyl flooring: $2.50-$5.50
    • Engineered wood flooring: $3.50-$7
    • Oak: $8-$15
    • Natural tile: $10-$25
  • Roofing: $1-$15
    • Asphalt shingles: $1-$3.50
    • Wood shingles and shakes: $3-$5.50
    • Metal: $3.50-$6
    • Slate: $4-$15
  • Frame: $15-$30 (including materials and labor)
    • Lumber costs fluctuate but are currently about $350.00 per 1,000 board feet
    • Steel frames cost about $1.50 per square foot

Holzapple says, “Most homeowners will try to match the existing construction of their home, so the cost of materials is often determined by what you already have in your house.”

Material cost also varies depending on market availability and national supply. For instance, due to supply chain disruptions related to the COVID-19 pandemic, 71% of U.S. contractors report facing material shortages, and the national average price for lumber increased by 130% in 2020.

Break down the cost to expand garage
Source: (vipman / ShutterStock)

The purpose of your extension

The purpose of your garage extension will determine what additional features you need, and these features can have a significant impact on the price. If you’re extending the garage for some extra storage space, you can expect fairly low construction costs. On the other hand, if you’re adding an office with its own bathroom, you’ll need to account for the cost of plumbing, heating, and air conditioning, electrical, insulation, flooring, and a door.

The most expensive garage extension you can build is an accessory dwelling unit. An ADU is a self-contained living unit, complete with a bathroom and kitchen. You’ll likely pay anywhere from $556 to $978 per square foot of new construction, well above the average for a standard garage extension.

Building site conditions

Baughman warns us that building on a slope will often increase the cost of construction and that if the slope is steep enough, the foundation will present contractors with a challenge, and an engineer will probably have to get involved.

Property lines

Property lines can also complicate construction, especially for homeowners whose home was built before local governments mandated property line setbacks. Setbacks increase the distance from the edge of your property in which new construction is allowed. If your garage was built before a property line setback, it was likely grandfathered in. However, if you modify your garage’s structure, the new frame must adhere to the new setback.

For example, if your existing garage extends beyond the property line on the left side and you want to expand the garage depth-wise, the added depth cannot cross over the property line on the left. You must set back the additional structure even if that means the extension is offset from the original structure.

Construction offsets may complicate building plans so you may need an architect or engineer to achieve a balanced, functional extension.

Local labor costs and permits

Finally, the cost of labor can vary depending on where you live. The best way to estimate labor costs is to request quotes from local contractors.

Additionally, you’ll likely need to pay for a permit to complete construction. While the exact price depends on your local government, the National Association of Home Builders reports that permit fees usually account for about 1.7% of construction projects’ total price.

Add up the cost to expand garage
Source: (GagoDesign / ShutterStock)

Adding garage space doesn’t just improve your life; it adds value to your home

The money you put into building your garage extension isn’t going to waste. On top of enjoying the benefits of added space, your addition will also add value to your home, increasing your equity and likely netting you a higher price at resale. According to The Nest, a garage extension typically yields a return of about 63.7% of the overall cost. This return is only slightly lower than the average ROI for a kitchen remodel, which recoups about 68.9% of its cost.

“An ADU is an income-generating investment, so it will have a more immediate return on investment,” says Baughman. “Other additions are dependent on the buyer. For example, if you turn your extension into a workshop, and your buyer does carpentry or hobbyist woodwork, that extension will have more value. If you add more garage space, a buyer who likes to work on cars will be willing to pay more for it.”

So, if you’ve found yourself yearning for more space, a garage extension could be a wise investment.

Header Image Source: (Zac Gudakov / Unsplash)