A Redmond home addition is one of the smartest ways to gain space without moving to a new house. Maybe you need a bigger kitchen, a new bedroom, or a home office. Whatever the goal, an addition lets you stay in the neighborhood you love while your home grows with your family.
Cost depends on the size, the type of addition, and your finishes. Because you are adding structure, electrical, and often plumbing, prices run higher than a simple remodel. Here are typical 2026 ranges:
These are general ranges, not quotes. For an exact price, request a free estimate and we will review your home and design goals with you.
Several factors move the number up or down. Foundation work, roofline changes, and matching existing siding all add labor. In addition, kitchens and bathrooms cost more because of plumbing and cabinetry. For a helpful cost breakdown, see this Cost vs. Value remodeling report.
An addition ties into your existing structure, so the work must be precise. A licensed builder protects your investment and keeps the project up to code. Look for these signs of a reliable contractor:
As a licensed general contractor, we manage the whole project — design, permits, foundation, framing, and finish — so you work with one team from start to finish.
There is more than one way to add space, so your builder should match the design to your home and lot. A bump-out extends a single room by a few feet and works well for kitchens. A single-room addition adds a full new space on the ground floor. A second-story addition builds up instead of out, which is ideal on smaller lots. Finally, a primary suite gives you a private bedroom and bath retreat.
Yes. Nearly every addition requires a building permit and plan review from the City of Redmond Residential Permits office. The review checks zoning, setbacks, and structural safety. A good builder pulls these permits for you and schedules the required inspections, so you are never left guessing.
Plan review in King County often takes four to ten weeks, depending on the project. Therefore, it pays to start early. We prepare your drawings and submit a complete package to reduce back-and-forth delays.
Most additions take three to six months from design to finish, plus permitting time up front. A small bump-out moves faster, while a second-story addition takes the longest because it involves more structural work. Because weather and material lead times matter, we build a realistic schedule and keep you updated at each stage.
How much does a home addition cost in Redmond?
Most additions run $180 to $400 per square foot in 2026. A single-room addition typically costs $40,000 to $120,000, based on size and finishes.
Do I need a permit for a home addition?
Yes. Almost every addition needs a City of Redmond building permit plus zoning and structural review. Your builder should handle permitting and inspections for you.
Is it cheaper to add on or move?
For many families, adding on costs less than buying a larger home once you factor in agent fees, moving costs, and higher prices. An addition also lets you stay in your neighborhood.
How do I choose a good addition builder?
Pick a licensed, bonded, and insured contractor with written estimates and local permit experience. Read our remodeling cost guide for more tips on vetting contractors.
Ready to add space? TJ Construction is a licensed, bonded, and insured builder serving Redmond, Sammamish, Bellevue, Kirkland, and the greater King County area. We give free, written, no-obligation estimates so you know exactly what your project will cost.
📞 Call or text 206-999-5442 · ✉️ service@tjconstructionwa.com