How much does a home addition cost?
A home addition often costs $125 - $250 per square foot. A 20x20 room addition commonly lands around $50,000 - $100,000, while second-story additions, in-law suites, kitchens, bathrooms, and high-end finishes can cost much more.
A real addition quote should make the structure clear: design, engineering, permits, excavation, foundation, framing, roofing, siding, windows, HVAC, electrical, plumbing, insulation, drywall, flooring, trim, paint, cleanup, and inspections.
Home addition cost by project type
Simple room addition
$125 - $250/sq ftHow to tellBedroom, office, family room, or flex space with limited plumbing and standard finishes
The fixPrice the square footage, foundation, framing, envelope, HVAC, electrical, and finishes together
Kitchen, bathroom, or primary suite addition
$175 - $350+/sq ftHow to tellThe new space needs plumbing, ventilation, tile, cabinets, fixtures, or upgraded electrical
The fixAdd wet-room allowances and confirm who coordinates each trade
Second-story addition
$200 - $500+/sq ftHow to tellExisting roof/structure changes and the home may need engineering or temporary relocation
The fixBudget for structural review, roof work, stairs, framing, utilities, and disruption
Garage, attic, or basement conversion
$50 - $200/sq ftHow to tellYou are converting existing space instead of adding a new footprint
The fixVerify ceiling height, insulation, egress, HVAC, electrical, and code requirements
Design, site prep, and permits
$3,000 - $20,000+How to tellPlans, survey, engineering, zoning review, excavation, foundation, or inspections are needed
The fixAsk whether preconstruction costs are included or separate
Before requesting home addition quotes
- Decide whether you are adding new square footage, converting existing space, or building up.
- Check zoning basics: setbacks, lot coverage, height limits, parking, easements, and HOA rules if applicable.
- Write down the room purpose, approximate dimensions, plumbing needs, HVAC needs, and finish level.
- Ask each contractor whether design, engineering, permit drawings, utility extensions, and inspections are included.
Unlock the hiring checklist
Use this before you call an addition contractor, so you know what to ask and what to avoid.
Call a pro when…
- The work changes the footprint, roofline, foundation, or structural load
- The space needs plumbing, HVAC, electrical, stairs, or egress
- Zoning, setbacks, permits, or inspections are required
- You need design-build coordination or architect/engineer input
- You are comparing build-up, build-out, garage conversion, attic conversion, or ADU options
Repair or replace?
Converting existing space can be cheaper if ceiling height, structure, egress, insulation, and utilities are already workable. Building new square footage is more flexible but usually costs more because it adds foundation, envelope, roofing, siding, and site work.
Need a cleaner scope before you call around?
Use the home additions checklist to compare the same work, questions, cleanup, and warranty before choosing a local company.
Related questions
Is it cheaper to build up or build out?
It depends on the house. Building up can avoid some foundation and site costs but may require major structural changes, roof work, stairs, and temporary relocation. Building out needs foundation and exterior work but may be simpler structurally.
What should a home addition quote include?
It should include design status, scope, exclusions, allowances, permits, site prep, foundation, framing, roofing, siding, windows, HVAC, electrical, plumbing, insulation, drywall, flooring, trim, paint, cleanup, schedule, and payment milestones.
Can I live in the house during an addition?
Often yes for a simple build-out, but major structural work, second-story additions, kitchen/bath additions, utility shutdowns, or heavy demo may require temporary relocation or a carefully phased plan.