There’s a moment most of our addition clients describe the same way: they’ve outgrown their house, but they love their neighborhood, their kids’ schools, their commute, their lot, their neighbors. They don’t want to move. They want their existing home to work harder.
That’s when a home addition becomes the conversation.
The question that follows immediately is, “What does it cost?” And the honest answer is more nuanced than a per-square-foot number, because not all square footage is created equal.
Here’s what a home addition in the Treasure Valley actually costs in 2026.
For most Boyd Remodeling and Construction additions, total project costs land in these ranges:
In 2026, here’s what we see across the region for new conditioned square footage tied into an existing Treasure Valley home:
Why the spread vs. new construction, which runs $225–$400/sq ft in the Treasure Valley? Three reasons:
For a representative $185K, 350 sq ft bedroom + half bath addition:
Some of our most efficient additions aren’t additions at all. They’re finishing existing unconditioned space. A 600 sq ft bonus room finish (insulation, HVAC, electrical, drywall, flooring, trim, often a closet and a half bath) typically runs $60K–$120K depending on finish level.
If you have unfinished space upstairs, in a basement, or above a garage, this is almost always the best cost-per-square-foot path to more living area in your home.
Detached and attached ADUs are an increasingly common request across Boise, Meridian, and Eagle, both for multigenerational living and short-term rental income. Our ADU services cover the full scope. A 600–800 sq ft detached ADU with full kitchen and bath typically runs $350K–$550K all-in, depending on whether utilities can be tied to the main home or need to run new from the street.
For a representative $185K, 350 sq ft bedroom + half bath addition:
A real addition timeline:
Total: 7–13 months from first call to certificate of occupancy
Before you commit to an addition, run the move comparison:
For many homeowners in Boise, Eagle, Meridian, and Nampa, a $200K–$300K addition compares favorably to or costs less than moving — and you keep your lot, your neighborhood, and the equity you’ve built. See examples of what we’ve built for Treasure Valley homeowners.
A real, well-built home addition in Boise and the Treasure Valley in 2026 starts around $90K for a basic bedroom and scales to $500K+ for a full master suite addition or second-story build-out. Per square foot, plan $250–$750 depending on whether the space includes plumbing.
If you’re weighing an addition vs. a move, we can build a comparison that includes both, and a fixed-price scope for the addition itself. Request a consultation or schedule a call with a remodeling expert. That’s a conversation worth having before you list your home.
