Accessory dwelling units (ADUs) cost $50,000 to $300,000 depending on size and type. A 500-square-foot garage conversion averages $70,000 to $150,000, while a new detached unit runs $150,000 to $300,000. Permits and design fees add 10-15%.
| Item | Typical range |
|---|---|
| ADU Total Cost Range | $50,000 - $300,000 |
| Garage Conversion Cost | $70,000 - $150,000 |
| New Detached ADU Cost | $150,000 - $300,000 |
| Permit and Design Fees | $3,000 - $15,000 |
Conversion vs. New Build Pricing
Converting existing space like a garage or basement costs $70,000 to $150,000 for 400-600 square feet. A new detached ADU typically costs $200 to $400 per square foot, so a 600-sq.-ft. unit might total $120,000 to $240,000.
Permits and Professional Fees
Building permits range from $1,000 to $5,000 depending on local codes. Architectural plans and engineering cost $2,000 to $8,000. Impact fees for water and sewer can add $3,000 to $10,000.
How to Budget for an ADU Project
Get at least three bids from licensed contractors. Include a 15% contingency for unexpected structural issues. A mid-range 400-sq.-ft. ADU might have a total budget of $100,000 to $160,000.
What moves the price in Alexandria, Virginia
Size, foundation type, and whether it's attached or detached matter. Local quotes reflect the items below, so two providers can quote different totals for the same described job without either being wrong.
- Local labour rates and licensing requirements for the trade or professional involved
- Permits, inspections and disposal fees set by the local authority
- Travel and call-out charges for the distance from the nearest provider
- Season and demand peaks, which move both the price and the wait
- Materials, parts or inputs, and how their grade or availability changes the total
- Whether the work is a repair, a partial job or a full replacement
How to compare adus quotes in Alexandria, Virginia
Write the scope down first, then send the same description to at least three local providers. Compare the quotes line by line against that scope rather than by the headline total.
- Agree the scope: exactly what is being repaired, replaced or supplied, and how far the work extends.
- List the inclusions: labour, materials, permits, inspection fees, disposal and clean-up, each stated separately.
- Ask what is excluded, and what would trigger an extra charge once the work starts.
- Check timing: how soon work can start, how long it takes, and whether out-of-hours rates apply.
- Confirm terms: deposit, payment schedule, warranty on parts and labour, and how changes are priced.
A lower total that leaves out permits, disposal or a necessary second stage is not cheaper once those items are added back. Ask each provider in writing what would change the price.
This page does not quote work and is not a contractor. The range above is an estimate, not an offer.
Common questions
What moves the price of adus in Alexandria, Virginia?
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