What a Room Addition Actually Costs in Fort Worth

Room additions are the single most cost-variable project in residential construction. A 300 sq ft addition can be $45,000 or $140,000 depending on what is in it. Pull up an online "average" and you will get an answer that does not apply to your house. Here is what actually drives the number in Fort Worth in 2026.

01Ballpark per-square-foot ranges

• Basic three-season sunroom (insulated walls, no HVAC, no plumbing): $150 to $220/sq ft
• Standard heated/cooled bedroom or office: $250 to $380/sq ft
• Master suite with full bath: $350 to $520/sq ft
• Kitchen expansion: $450 to $700+/sq ft (cabinetry and appliances drive the number)

A 400 sq ft master suite at $420/sq ft is $168,000. A 400 sq ft three-season room at $180/sq ft is $72,000. Same footprint, completely different scope.

02The line items that move the number

1. 1Foundation type — slab on grade is cheapest, pier-and-beam to match existing structure costs more
2. 2Roof tie-in — matching a complex existing roofline (gables, dormers) is significantly harder than a simple shed-roof addition
3. 3HVAC — extending existing system vs. adding a new mini-split vs. a full new system
4. 4Plumbing — none vs. half bath vs. full bath with shower (drainage routing is a big driver)
5. 5Electrical — basic 15-amp lighting vs. dedicated circuits for appliances or workshop tools
6. 6Finishes — builder-grade vs. custom (tile vs. luxury vinyl, mid-range cabinets vs. custom millwork)

03The permitting reality

Fort Worth requires permitting and inspection on any addition that increases the conditioned square footage of the home. Engineering stamp required if the addition modifies load-bearing structure. Plan-check fees, permit fees, and impact fees together run $1,500 to $4,500. Budget for it.

Some contractors offer "no-permit pricing." Pass. An addition without a permit becomes a liability when you sell the house, and the city will eventually find it through aerial inspection.

04A realistic schedule

• Design and engineering: 3 to 6 weeks
• Permitting: 4 to 10 weeks
• Foundation: 1 week
• Framing through dry-in: 2 to 3 weeks
• Interior finish (drywall, flooring, paint, trim): 4 to 8 weeks
• Total elapsed: 4 to 7 months from contract signing