Home Additions and ADU Construction
More space without moving. Room additions, ADUs, and expansions for Eastside homes.
Adding On Makes More Sense Than Moving
Home prices on the Eastside make moving expensive. Between closing costs, real estate commissions, and the stress of uprooting your family, a well-planned addition often costs less than buying a bigger house in the same neighborhood. We build room additions, second-story expansions, garage conversions, and accessory dwelling units for homeowners who love their location but need more space. Kirkland's zoning has become more ADU-friendly in recent years, and we stay current on setback rules, height limits, and lot coverage maximums so your project gets approved without delays.
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Running Out of Room in Your Current Home?
Growing families hit a wall eventually. The kids need their own bedrooms. You need a home office that is not the dining room table. An aging parent needs accessible living space on the main floor. Or maybe you want rental income from an ADU on your property. The homes in Totem Lake, Juanita, and Rose Hill were built for smaller families and shorter commutes. Now that more people work from home and families are staying put longer, the square footage does not match the need. An addition solves that without giving up the neighborhood, the school district, or the commute you have already dialed in.
Avoiding the Most Common Addition Mistakes
The biggest risk with home additions is starting construction and finding out you violated a setback requirement or exceeded lot coverage. That stops the project cold and can require expensive redesign. We verify all zoning constraints before we draw plans. The second most common mistake is underestimating foundation requirements. Kirkland has varied soil conditions, and some areas have high water tables or clay soils that affect foundation design. We work with geotechnical reports when needed and size foundations appropriately. Third, a bad tie-in between old and new construction creates leaks. Our roofers integrate new flashing and roofing materials with the existing structure to prevent water intrusion at the connection point.
What We Build
We handle additions from foundation to finish. That includes structural engineering, permitting, and all the trades in between.
- •Room additions (bedroom, family room, home office)
- •ADU construction (detached, attached, and garage conversions)
- •Second-story additions with structural reinforcement
- •Foundation work (crawl space and slab-on-grade)
- •Structural engineering and load calculations
- •Roofing tie-in to existing structure
- •Siding matching to blend with original home exterior
- •Electrical, plumbing, and HVAC extension into new space
Every addition is designed to look like it was always part of the house. We match siding, roofline, and trim details so the new space blends with the original construction.
How We Plan and Build Additions
Additions are more complex than interior remodels because you are working with foundations, structural loads, rooflines, and exterior systems. We start with a site assessment to determine what is feasible given your lot, zoning, and budget. Then we work with a structural engineer to design the addition and produce plans for permit review. City of Kirkland permit turnaround for additions is typically 4 to 8 weeks, sometimes longer if design review is required. Once permits are in hand, foundation work starts first, followed by framing, roofing, siding, and then interior build-out. A typical room addition takes 3 to 5 months from permit approval to completion. ADUs generally run 4 to 6 months.
Site Assessment
Evaluate lot, zoning, and feasibility for the addition or ADU
Design and Engineering
Structural plans, architectural drawings, and permit submission
Foundation
Excavation, footings, and foundation pour or crawl space build
Framing and Exterior
Walls, roof, siding, windows, and weather barrier
Interior and Finish
Systems, insulation, drywall, flooring, and final walkthrough
What Sets Us Apart
- ✓Structural engineer on every addition project
- ✓Zoning research and setback verification before design starts
- ✓Permit management with City of Kirkland building department
- ✓Foundation design matched to soil and drainage conditions
- ✓Roofline and siding matching so the addition looks like it was always part of the house
- ✓Washington energy code compliance (R-38 ceiling, R-21 wall)
- ✓Single point of contact for the entire project
Home Additions Across the Eastside
We build additions throughout the Kirkland area. Zoning rules vary by city, and we know the requirements for each.
Kirkland
ADU-friendly zoning with recent code updates. We stay current on lot coverage and setback rules.
Redmond
Expanding ADU allowances. Larger lots in Education Hill and Bear Creek offer good addition opportunities.
Woodinville
Rural properties with acreage. Septic capacity and well water considerations for ADU projects.
Bothell
Mix of King and Snohomish County zoning. We verify which jurisdiction applies to your property.
Bellevue
Strict design review in some neighborhoods. We navigate the process and submit compliant plans.
Kenmore
Smaller lots near the lake with specific height and setback constraints we account for.
Home Addition and ADU Costs
Room addition (200-400 sq ft)
$80,000 to $150,000
Detached ADU (400-800 sq ft)
$150,000 to $300,000
Second-story addition
$200,000 and up
Factors affecting pricing: Addition costs depend on foundation type, square footage, structural complexity, and finish level. A slab foundation costs less than a full crawl space. Second-story additions require structural reinforcement of the existing first floor which adds cost. ADUs with full kitchens and bathrooms cost more per square foot than simple room additions.
What's included: Estimates include structural engineering, permits, all construction from foundation through finish, and inspections. Site work and utility connections are itemized separately because they vary significantly by property.
25 reviews
Trusted by Homeowners Throughout the Puget Sound
Jeremiah Graziano
Kirkland, WA
Local Guide
ProBuild Solutions handled our kitchen and bathroom remodel with exceptional attention to detail. Thomas demonstrated outstanding transparency throughout the project. His communication was clear and consistent, and the meticulous work quality exceeded our expectations. Every aspect of the remodel was executed to the highest standard.
Elias Ioach
Kirkland, WA
Our full bathroom remodel was an incredible transformation. From the initial consultation to final walkthrough, ProBuild Solutions maintained professionalism and quality. The team worked efficiently and delivered results that completely transformed our space.
David Termure
Kirkland, WA
Needed a shed demolition and was impressed by how quickly Thomas responded to our initial inquiry. He provided a quick, accurate quote and the work was completed professionally. The responsiveness and attention to detail set ProBuild Solutions apart.
Hendryw Lucas
Bothell, WA
ProBuild Solutions remodeled our master and guest bathrooms beautifully. The team maintained great communication throughout the project and finished exactly on schedule. We appreciated their professionalism and expertise.
Chloe Anderson
Kirkland, WA
We had ProBuild Solutions handle a full house remodel including two bathrooms, our kitchen, and all flooring. Thomas and his team managed the entire project seamlessly. They coordinated every aspect of the work, and the results speak for themselves.
Wendy Smith
Redmond, WA
Our full kitchen remodel in Redmond turned out beautifully. ProBuild Solutions handled the project professionally from start to finish. The quality of work and attention to detail were exceptional.
Aurelio Samano
Kirkland, WA
ProBuild Solutions built a new deck that passed inspection on the first try. Thomas and the team demonstrated professional expertise and knowledge of local building codes. The work was completed to the highest standards.
Lori
Kirkland, WA
Thomas did a fantastic job on our bathroom remodel. His clear communication, transparent pricing, and commitment to finishing on time made the process smooth and stress-free. We would highly recommend ProBuild Solutions.
Jasraj Dange
Kirkland, WA
Local Guide
ProBuild Solutions installed new windows and expanded our kitchen window beautifully. Thomas and Ben were responsive and knowledgeable. Their competitive pricing combined with professional service made them the clear choice.
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Frequently Asked Questions
Let's Start Your Home Additions Project
Call us at (425) 435-5347 or fill out the form for a free on-site estimate with line-item pricing.