Home Additions
Serving Maple Valley, Renton, Kent, Covington & Issaquah
About Our Home Additions Services
When your family outgrows your home, a well-planned addition can provide the extra space you need without the hassle of moving. A. Sanders Construction builds custom home additions throughout Maple Valley, Renton, Kent, Covington, and Issaquah. We construct room additions, bump-outs, second-story additions, sunrooms, and accessory dwelling units (ADUs) that blend seamlessly with your existing home. Every addition project begins with careful planning to ensure structural integrity, code compliance, and architectural harmony with your home's existing design. We manage the entire process including architectural coordination, permit acquisition, foundation work, framing, roofing, siding, electrical, plumbing, insulation, drywall, and interior finishing. As a licensed general contractor with deep experience in King County building requirements, we navigate the permitting process efficiently and build additions that add significant value to your property.
What We Offer
Our Process
Consultation to discuss your space needs, budget, and design preferences.
Architectural planning and structural engineering coordination.
Permit applications and approvals through King County.
Site preparation, foundation, and framing.
Roofing, siding, windows, and exterior finishing.
Interior build-out: electrical, plumbing, insulation, drywall, and finishing.
Project Gallery
Areas We Serve
We provide home additions services throughout South King County, Washington.
Frequently Asked Questions
How much does a home addition cost in King County WA?
Home additions in King County typically cost $150-$400 per square foot depending on complexity, finishes, and whether plumbing is involved. A basic 200 sq ft room addition might start around $40,000, while a full second-story addition can exceed $200,000. We provide detailed estimates after an on-site consultation.
Do I need permits for a home addition?
Yes, all home additions in King County require building permits, and most require engineering plans. A. Sanders Construction handles the entire permit process for you, including applications, plan submissions, and scheduling inspections.
Can you build an ADU on my property?
Yes, we build detached and attached ADUs (accessory dwelling units). Recent Washington state legislation has expanded ADU allowances. We'll evaluate your property's zoning, setback requirements, and utility connections during a free consultation.
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Energy-efficient windows that improve comfort and reduce utility costs.
Get Started on Your Home Additions Project
Contact A. Sanders Construction today for a free, no-obligation estimate. Licensed contractor ASANDSC9210K serving South King County.