Room Addition Cost Calculator: Plan Your Home Expansion with Confidence

The cost of adding a room varies wildly depending on whether you are building up or building out. On average, homeowners should expect to spend between $250 and $600 per square foot for a professional, permitted addition.

Average Cost by Addition Type

• The Bump-Out ($15,000 - $35,000): A small extension (typically 2-10 feet) that expands an existing room like a kitchen or bathroom. This is the most cost-effective way to add "breathing room."
• The Ground-Level Addition ($40,000 - $150,000): Building a new room on a new foundation. This is the standard for a new primary suite or family room.
• The Second-Story Addition ($100,000 - $350,000): Building up is often more expensive than building out because it requires reinforcing your existing first-floor walls and foundation to support the new weight.
• The Garage Conversion ($15,000 - $45,000): Converting existing "cold" space into living space is a high-ROI move for creating Zoned Living areas.

In 2026, your budget isn't just about lumber and drywall. Here are the "Heavy Hitters" that will influence your final quote:

• Foundation & Site Work (15-20%): If you are building "out," you need to excavate and pour concrete. If your site has poor drainage or utility lines in the way, this can escalate quickly.
• Structural Integration (20-25%): The most expensive part of an addition is where the "new" meets the "old." This requires careful engineering to ensure the rooflines and floor levels align perfectly.
• HVAC and Utilities (10-15%): Will your current furnace handle the extra square footage? In 2026, many homeowners are opting for Aerothermal Heat Pumps for their additions to avoid overloading their main systems.
• Permits and Professional Fees (5-10%): You will likely need an architect and a structural engineer. USIC utility markings are a mandatory first step before any digging begins.

Adding square footage is the single most reliable way to increase your home's PICO™ Property Condition Score. In 2026, we've found that the highest ROI comes from:

• Primary Suite Additions: 65% - 75% ROI.
• Bathrooms: Adding a second or third bathroom can offer up to an 80% ROI.
• Multigenerational Suites: With the rise of the "Forever Home," additions with Universal Design features are in high demand.

According to research from the National Association of the Remodeling Industry (NARI), homeowners consistently report a "Joy Score" of 9 or 10 after completing an addition, making it a win for both your bank account and your quality of life.

Q: Is it cheaper to build up or build out?

A: Usually, building out (ground floor) is cheaper because it doesn't involve tearing off your existing roof or reinforcing the first-floor structure. However, if your lot is small or has steep slopes, building up might be your only option.

Q: How do I finance a $100,000 addition in 2026?

A: Most homeowners use a HELOC or a Renovation Loan. Because additions increase the home's value significantly, lenders are often willing to lend based on the "After-Repair Value" (ARV).

Q: Do I need an architect for a room addition?

A: For anything structural, yes. An architect ensures that the addition is safe, matches your home's existing Heritage Modern or contemporary style, and meets all 2026 building codes.

Q: Will an addition increase my property taxes?

A: Yes. Because you are adding livable square footage, your local tax assessor will eventually re-evaluate your home. However, the increase in equity almost always outweighs the tax hike.

Don't let the complexity of a room addition stop you from creating the space you need. Use the Kukun Room Addition Cost Calculators above to get an instant, localized estimate. We'll show you the costs, the ROI, and help you find the vetted contractors who can turn your blueprints into reality.