Home Addition Architect in Seattle & Kirkland WA — Piper Cole Architects

A well-designed home addition gives you the space you need without the disruption of moving. Whether you are adding a primary suite, expanding your kitchen, building a second story, or creating a dedicated home office, Piper Cole Architects designs home additions across the Seattle metro area that feel like they were always part of the original house.

Types of Home Additions We Design

• Second Story Additions — Add a full upper floor or partial second story to a single-story home
• Primary Suite Additions — Main floor or upper level master bedroom with private bath
• Kitchen Additions — Expand and reconfigure your kitchen with a full room addition
• Home Office Additions — Detached studio or attached dedicated office space
• Family Room and Great Room Additions — Open the back of the house with a large, light-filled space
• In-Law Suites — Ground-level accessible suites for multigenerational living

Home Addition Costs in Seattle (2026)

• Primary suite addition (400 sq ft): $175,000 to $280,000
• Second story addition (full floor): $350,000 to $600,000+
• Kitchen addition (250 sq ft): $120,000 to $200,000
• Home office studio (detached, 200 sq ft): $90,000 to $165,000
• Architect design fees: $18,000 to $55,000 depending on scope

Permitting for Home Additions in Seattle

All structural home additions in Seattle, Kirkland, Bellevue, and surrounding jurisdictions require a building permit with full architectural drawings. Piper Cole Architects prepares complete, code-compliant permit submissions and manages the review process. Standard residential additions in Seattle typically take 6 to 10 weeks for permit review.

Free Consultation

Contact Piper Cole Architects for a free initial consultation. We will review your existing home, discuss your goals, and give you a realistic picture of schedule, budget, and process.

Call: 425-753-6452 | Kirkland, WA | Serving the entire Seattle Eastside

Frequently Asked Questions

How much does a home addition cost in Seattle?

Home additions in the Seattle area in 2026 typically run $350 to $650 per square foot. A primary suite addition runs $175,000 to $280,000, a full second story $350,000 to $600,000+, and a kitchen addition $120,000 to $200,000.

Do I need an architect for a home addition?

Yes. All structural home additions in Seattle and the Eastside require a building permit with full architectural drawings. An architect ensures the addition integrates with your existing home, meets energy and structural code, and is documented for accurate construction.

How long does a home addition take?

Design and permitting typically take 4 to 7 months and construction adds 3 to 8 months depending on scope. A small addition can reach move-in in about 9 to 12 months; a full second story takes 16 to 22 months.

Will I have to move out during construction?

For ground-floor additions, families can often stay in the home. For a full second story, the roof is removed during construction, so most homeowners relocate for 4 to 8 months.