What a home addition costs

Published home addition cost ranges

On its home addition page, updated May 30, 2026, Angi publishes an average of $50,994, says most projects fall between $21,895 and $83,355, and lists as little as $4,000 for a small bump-out. For Austin, the Angi Austin room additions page, updated June 29, 2026, publishes an average of $47,088 and a typical range of $20,503 to $71,221.

The Fixr house addition page, updated February 3, 2025, publishes a range of $30,000 to $100,000 and an average of $65,000. For a 300-square-foot first-floor family room, Fixr puts the cost at about that average.

On its home addition page dated January 8, 2024, HomeGuide publishes a range of $18,000 to $36,000 for a 12x12 room addition and $50,000 to $100,000 for a 20x20 room addition. The published range is higher for the 20x20 room addition.

Home addition cost per square foot

Angi, updated May 30, 2026, lists $80 to $200 per square foot for building out and $300 to $500 per square foot for building up, and gives an average of $12,500 built out and $40,000 built up for a 10x10 room. For a room addition in Austin, Angi Austin room additions, updated June 29, 2026, lists $80 to $195 per square foot.

For a room addition, HomeGuide, January 8, 2024, publishes a range of $125 to $250 per square foot and puts a second story at $200 to $500 or more per square foot. Fixr, updated February 3, 2025, lists $100 to $300 per square foot for a finished addition.

Bedrooms, bathrooms, and second stories

Angi’s bedroom addition page, updated September 24, 2026, lists a national average of $50,000, says most bedroom additions cost $20,000 to $130,000, and gives a range of $100 to $500 per square foot.

Angi’s bathroom addition page, updated July 10, 2026, lists an average of $35,000, says most bathroom additions cost $5,000 to $75,000, and gives a range of $400 to $550 per square foot. Fixr’s bathroom addition page, updated January 22, 2026, lists $200 to $250 per square foot to convert existing space into a bathroom and $400 to $550 per square foot to build one in a new addition. The Remodeling 2025 Cost vs. Value Report at www.costvsvalue.com lists $50,804 in Austin and a $60,645 national average for a midrange bathroom addition consisting of a 6-by-8-foot bathroom over a crawlspace with a fiberglass tub and shower and a ceramic tile floor.

Angi’s Austin second-story page, updated May 21, 2026, lists an average of $171,675, says most second-story additions cost $98,100 to $245,250, and gives a range of $100 to $300 per square foot, up to $500 per square foot for larger, more customized builds. Angi also lists foundation support work at $5,000 or more.

Garage conversion cost

Published garage conversion costs give you national and Austin reference points. Angi garage conversions, updated August 31, 2026, publishes a national average of $16,474, with most conversions at $6,003 to $27,348, and about $40 per square foot within a $25 to $75 per-square-foot range. Angi lists a one-car garage (240 square feet) around $9,600, a two-car garage (440 square feet) around $17,600, and permits at $300 to $1,000. For Austin, Angi Austin garage conversions, updated January 29, 2026, publishes an average of $11,960, with most conversions at $3,900 to $20,020, a range of $24 to $73 per square foot, a bedroom at $11,640, a bedroom and bathroom at $24,250, and an in-law suite at $29,100.

HomeGuide garage conversions, August 22, 2025, publishes $5,000 to $17,000 for converting a garage to a bedroom and $20,000 to $100,000 or more for converting one to an apartment or in-law suite, covering framing, drywall, a bathroom and kitchen, and heating and cooling. See how we handle garage conversions.

What moves the price

For an addition, Angi’s home addition page, updated May 30, 2026, lists an architect’s design fee at $2,400 to $14,000, site prep at $1,500 to $5,000, and building permits at an average of $1,300, from $150 in rural areas to $7,500 in some cities. For a primary suite, Angi Austin room additions, updated June 29, 2026, puts bathroom plumbing at about $1,470 to $3,920 on top of the addition.

The City of Austin Development Services Department’s Residential Plan Review lists extra reviews that can apply when we build home additions. A tree review can apply when trees 19 inches or more in diameter are on or next to the property. A historic review can apply to structures 45 years old or older when the exterior is demolished or modified. A floodplain review can apply inside the 100-year floodplain or within 100 feet of it.