Garage Construction & ADUs Cost Guide — Seattle, WA

Verified 2025 pricing for garage construction & adus services in Seattle. Updated quarterly from local contractor data.

Service Cost Ranges

Service	Low	Average	High	Unit
Detached Garage Construction	$29,000	$65,250	$145,000	per project
ADU / Garage Apartment	$87,000	$174,000	$362,500	per project
Carport Installation	$5,800	$13,050	$36,250	installed

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Older housing stock (pre-1968) increases complexity and materials cost

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High provider competition keeps pricing competitive vs national averages

✓Get at least 3 quotes

✓Ask about seasonal discounts

✓Bundle multiple services

✓Check for manufacturer rebates

✓Verify license before hiring

See who offers the best value for money in Seattle.