How much does home addition cost?
A home addition costs $45,000 to $140,000, averaging about $85,000. That is $150 to $450 per square foot — more than new construction, because you are tying into an existing structure.
National average
$85,000
Typical low
$45,000
Typical high
$140,000
Per square foot
$150 – $450
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Estimated project cost
$40,000 – $100,000
Most homeowners pay around $70,000
Compare addition type
Cost by material
Installed pricing per square foot.
| Option | Installed cost |
|---|---|
| Garage conversion | $80 – $200 |
| Sunroom | $100 – $250 |
| Bump-out | $150 – $350 |
| Single-room addition | $150 – $400 |
| Second story | $200 – $500 |
| In-law suite / ADU | $180 – $450 |
Cost by addition size
| Size | Typical use | Cost range |
|---|---|---|
| 100 sq ft | Bathroom or bump-out | $15,000 – $45,000 |
| 200 sq ft | Bedroom | $30,000 – $80,000 |
| 400 sq ft | Master suite or family room | $60,000 – $160,000 |
| 600 sq ft | In-law suite | $90,000 – $270,000 |
| 1,000 sq ft | Second story or wing | $150,000 – $450,000 |
Timeline expectations
| Phase | Duration |
|---|---|
| Design and engineering | 3 – 8 weeks |
| Permitting | 2 – 12 weeks |
| Foundation and framing | 3 – 6 weeks |
| Mechanical rough-in and inspection | 2 – 4 weeks |
| Finishes | 4 – 10 weeks |
| Total | 4 – 9 months |
Where the money goes
A typical project budget, broken down by line item.
- Labor38% · $32,300
- Materials32% · $27,200
- Mechanical, electrical, plumbing15% · $12,750
- Design, permits and engineering9% · $7,650
- Site work and foundation6% · $5,100
Cost by region
Labor markets move the number more than any other single factor.
Northeast metro
$56,250 – $175,000
+25% vs. national average
West Coast metro
$58,500 – $182,000
+30% vs. national average
Mountain West
$48,600 – $151,200
+8% vs. national average
Midwest
$45,000 – $140,000
At the national average
South & Southeast
$41,850 – $130,200
-7% vs. national average
Rural nationwide
$40,500 – $126,000
-10% vs. national average
Common add-ons
Line items that show up on most quotes but rarely in the headline price.
Architect and engineering
New bathroom
Kitchenette
HVAC system expansion
Electrical panel upgrade
Temporary housing during work
DIY vs. hiring a pro
Hire a pro
$45,000 – $140,000
Do it yourself
$25,000 – $80,000
Owner-builder can cut 15% to 25% by managing subs yourself, but you take on permitting, scheduling, liability and lender scrutiny. Structural, electrical and plumbing must still be licensed and inspected.
Ways to save
Practical levers that lower the bill without cutting quality.
- Build up or bump out rather than adding a new foundation footprint.
- Keep plumbing on the existing wet wall — moving water and waste lines is the costliest change.
- Convert existing space (garage, attic, basement) at half the per-square-foot cost.
- Keep the roofline simple; complex tie-ins add framing labor and leak risk.
- Lock the design before demolition — change orders during construction carry the biggest premiums.
Questions to ask your contractor
- 01Is this a fixed-price contract or cost-plus, and what is the contingency?
- 02Who handles architectural drawings, engineering and permits?
- 03How will you tie the new roof and foundation into the existing structure?
- 04Can my current HVAC and electrical service handle the added load?
- 05What is the payment schedule tied to, and is there a lien waiver process?
- 06What is the completion date and what are the penalties for delay?
Frequently asked questions
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Get addition quotesHome Addition cost by city
Local labor rates, permits and climate change the number. Pick your city for prices near you.
Home Addition cost in Los Angeles, CA
$55,800 – $173,600
Home Addition cost in San Diego, CA
$53,100 – $165,200
Home Addition cost in San Jose, CA
$62,100 – $193,200
Home Addition cost in San Francisco, CA
$65,250 – $203,000
Home Addition cost in Oakland, CA
$59,400 – $184,800
Home Addition cost in Sacramento, CA
$48,600 – $151,200
Home Addition cost in Fresno, CA
$44,100 – $137,200
Home Addition cost in Long Beach, CA
$54,900 – $170,800
Home Addition cost in Anaheim, CA
$54,000 – $168,000
Home Addition cost in Santa Ana, CA
$53,550 – $166,600
Home Addition cost in Irvine, CA
$56,700 – $176,400
Home Addition cost in Riverside, CA
$47,700 – $148,400
Home Addition cost in San Bernardino, CA
$46,350 – $144,200
Home Addition cost in Bakersfield, CA
$43,650 – $135,800
Home Addition cost in Stockton, CA
$45,900 – $142,800
Home Addition cost in Modesto, CA
$45,000 – $140,000
Home Addition cost in Chula Vista, CA
$51,750 – $161,000
Home Addition cost in Fremont, CA
$60,750 – $189,000
Home Addition cost in Pasadena, CA
$57,600 – $179,200
Home Addition cost in Glendale, CA
$56,250 – $175,000
Home Addition cost in Santa Clarita, CA
$52,200 – $162,400
Home Addition cost in Torrance, CA
$55,350 – $172,200
Home Addition cost in Oxnard, CA
$51,300 – $159,600
Home Addition cost in San Mateo, CA
$63,000 – $196,000