House Extensions in the Seattle–Tacoma area
A house extension pushes your walls outward — extending the kitchen into the yard, deepening the living room, stretching the primary suite — to gain exactly the space you need where you need it, while keeping the home you already love.
The overview
Our approach to house extension
Extensions are the surgical option among home expansions: rather than adding a separate wing or a new level, we move an exterior wall outward and enlarge the rooms that feel tight. Done well, a rear or side extension transforms a cramped kitchen into an entertaining hub or a modest bedroom into a true suite, with the gained footage flowing naturally into the existing plan.
The craft lies at the seam. Extending a footprint means new foundation work tied to old, roof planes extended or blended, and floor levels meeting perfectly — details our five generations of building experience have refined into routine. Our in-house 3D design team plans the extension against your lot's setbacks and drainage patterns, showing you the extended rooms and the new exterior before construction.
Serving Milton, Edgewood, Fife, and communities across the Seattle-Tacoma region, we manage design, engineering, permits, and construction under one contract (license HOMERDB750MH), with financing assistance available.
A note from Donovan
Your house extension, treated like it's our own home.
I'm Donovan. My family has been building across the South Sound for five generations, and every house extension project we take on gets the same promise: an honest budget range, a design you can walk through in photorealistic 3D before we build it, and a crew that treats your house the way we'd treat our own.
You won't be handed off to a call center or a stranger with a clipboard. You'll work with the same family that's earned its reputation one neighbor at a time — and we don't consider the job done until it feels like home.
— Donovan
Owner & Lead Designer · Licensed WA #HOMERDB750MH
Free design consultation
Tell us about your house extension project and Donovan's team will reply within one business day — no obligation, just honest advice.
Why choose us
What sets our house extension apart
Kitchen & Living Extensions
Rear extensions that push your main living spaces toward the yard — bigger kitchens, dining that seats everyone, and glass that pulls the landscape in.
Bedroom & Suite Stretches
Extending a bedroom wall a few strategic feet creates walk-in closets and ensuite baths a fixed footprint could never fit.
Foundation-to-Roof Integration
New footings tied correctly to existing foundations and roofs extended in matching pitch and material — the structural seam done right.
Site & Drainage Planning
We design around Puget Sound rainfall from the start: grading, gutters, and drainage that protect both the extension and the original house.
Light-Focused Design
Extensions can darken interior rooms if planned poorly — our designers use glazing, roof windows, and open sightlines to make the whole floor brighter.
Setback & Zoning Navigation
We confirm your buildable envelope with the local jurisdiction before design, so the plan you fall for is a plan you can build.
How it works
Our design-build process
Site & Feasibility Review
We measure your lot's setbacks, coverage limits, and drainage conditions to define exactly how far your walls can move.
Extension Design
Floor plans and 3D renderings show the extended rooms, the new exterior, and how gained space reshapes daily life.
Engineering & Permits
Foundation and structural design, energy compliance, and permit approvals are handled fully in-house.
Construction
Excavation, foundation, framing, and weatherproofing proceed outside your existing envelope; the wall opening comes late and briefly.
Blend & Finish
Flooring, trim, and finishes are blended across old and new so the extension disappears into the home, followed by walkthrough and warranty.
When the tools come down and the crew heads home, what's left is yours — a house that finally feels like home.
Donovan& the crew
Start your house extension projectFAQs
House Extension questions
What is the difference between an extension and an addition?
An extension enlarges existing rooms by moving their exterior walls outward, while an addition typically creates new rooms in a new structure or level. Extensions shine when the rooms you have are right — just too small.
How much does a house extension cost?
Most extensions run $350 to $600+ per square foot depending on foundation conditions and whether kitchens or baths are involved. Because extensions concentrate value in high-impact rooms, even modest footage transforms how a home lives. Financing assistance is available.
How close to my property line can I build?
Each jurisdiction sets its own setbacks by zone — commonly 5 to 25 feet depending on the yard. We verify your parcel's exact rules during feasibility, and design the extension to use every legal foot wisely.
Will my yard drainage be affected?
Any footprint increase changes how water moves on your lot, which is exactly why we engineer grading, downspouts, and drainage as part of the design rather than an afterthought — essential in our rainfall.
Can I stay home during an extension project?
Yes — this is one of an extension's advantages. Nearly all work happens outside your sealed exterior wall, which we open only in the final weeks to join the spaces.
How long does a house extension take?
Typical projects run six to ten weeks of design and permitting followed by three to five months of construction, depending on size and how much interior blending the plan includes.