What Does a Home Addition Contractor Do?

A home addition contractor manages the design, planning, and construction of new living space added to your existing home. Unlike piecemeal remodeling, a professional design-build contractor ensures your addition blends seamlessly with your home’s layout, systems, and architectural style.

Common home additions in Lake Oswego include:

  • Primary suite additions
  • Kitchen expansions
  • Second-story additions
  • ADUs and guest suites
  • Home offices and flex spaces
  • Garage conversions and expansions

Why Build a Home Addition in Lake Oswego?

Lake Oswego homeowners often choose additions as a strategic alternative to moving in a competitive, high-value housing market.

Top reasons include:

  • Increasing livable square footage without relocating
  • Adapting the home for changing lifestyle needs
  • Creating multigenerational living solutions
  • Enhancing property value in a premium market
  • Customizing the home to fit long-term plans

 

 

Types of Home Additions We Do in Lake Oswego

The Lamont Bros. Design & Construction team designs and builds a range of additions in Lake Oswego, such as bathroom and kitchen additions, primary suite additions, ADUs and guest spaces, garage and basement conversions and more. 

Main-Level Additions

Expand your footprint to create larger kitchens, living rooms, or new functional spaces that improve flow and usability.

Second-Story Additions

Add significant square footage without expanding your home’s footprint—ideal for maximizing smaller lots in Lake Oswego.

Primary Suite Additions

Create a private retreat with a spacious bedroom, en suite bathroom, and walk-in closet.

ADUs & Guest Suites

Add independent living spaces for guests, rental income, or multigenerational living.

Garage Conversions & Expansions

Transform underutilized garage space or expand it into livable square footage.

How Much Do Home Additions Cost in Lake Oswego? 

The cost of a Lake Oswego home addition will range from around $100,000 to $400,000+, depending on the size of the addition, structural requirements, and the level of interior finishes.

Projects that involve major structural changes, such as second-story additions or large kitchen expansions, usually fall on the higher end due to engineering, roofing adjustments, and system upgrades.

 

What Factors Influence the Cost of a Lake Oswego Home Addition?

The factors that influence the cost of a home addition include structural engineering requirements, foundation work, roof modifications, plumbing and electrical upgrades, finish quality, and custom design features.
 
The most accurate pricing comes from a feasibility consultation and on-site evaluation where we review your home’s structure, layout, and project goals.
 

Typical Lake Oswego Home Addition Cost Ranges

  • Small bump-out addition: $100,000 – $175,000

  • Kitchen or living room expansion: $175,000 – $275,000

  • Primary suite addition: $200,000 – $350,000

  • Second-story addition: $250,000 – $400,000+

Want a personalized estimate? Try Our Home Addition Cost Calculator

Why Choose Lamont Bros. as Your Lake Oswego Home Addition Contractor?

Lamont Bros. Design & Construction has been remodeling high-end homes in the Portland metro area since 2008. With a 4.8/5 star average customer rating, we're one of Lake Oswego's top design-build contractors.

Our design-build process means there are no financial surprises once we've nailed down the project specifications. Here's why Lake Oswego homeowners choose Lamont Bros. for their home remodeling projects: 

  • Proven design-build expertise
  • Deep experience with complex additions and structural projects
  • Transparent pricing and process
  • Strong understanding of Lake Oswego zoning and permitting
  • Commitment to craftsmanship and client experience
Lake Oswego home addition contractors
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Lake Oswego's  Favorite Home Addition Contractor

Lamont Bros. Design & Construction builds custom home additions throughout Lake Oswego using our design-build process. 

 

Lamont Bros. Design & Construction

Lake Oswego Remodeling | Home Addition Portfolio

These additions across the Portland metro area include second-story additions, basement build-outs, built extra bathrooms, and more. 

More Projects
Sweet Green Second-Story Addition
Addition

Sweet Green Second-Story Addition
Garden Home Whitford Kitchen Addition
Kitchen

Garden Home Whitford Kitchen Addition
Portland Garage Conversion
Addition

Portland Garage Conversion
Oregon City Mother In Law Suite Addition
Addition

Oregon City Mother In Law Suite Addition
A Chef's Kitchen
Kitchen

A Chef's Kitchen
Hillsboro Second-Story Addition
Addition

Hillsboro Second-Story Addition

Damascus Single-Level Home Addition
Addition

Damascus Single-Level Home Addition

Lake Oswego | Home Addition Construction

Frequently Asked Questions

How much does a home addition cost in Lake Oswego?

Home addition costs in Lake Oswego typically range from $100,000 to $400,000+, depending on size, structural complexity, and finish level.

Lamont Bros. Design & Construction provides detailed, design-driven estimates to align scope and budget early.

Try our Home Addition Cost Calculator

How long does a home addition take from start to finish?

Most home additions take 6–10 months for construction, plus 2–4 months for design and permitting; Lamont Bros. Design & Construction manages the full timeline to reduce delays and keep the project on track.

Can I live in my home during a home addition project?

In many cases you can remain in your home, but it depends on how the addition ties into existing living areas; Lamont Bros. Design & Construction plans phasing and site logistics to minimize disruption when occupancy is possible.

What type of home addition adds the most value?

Primary suite additions, kitchen expansions, and well-designed second-story additions typically deliver the strongest resale value; Lamont Bros. Design & Construction prioritizes layouts and features that improve both daily livability and long-term ROI.

Do I need permits for a home addition in Lake Oswego?

Yes, all structural home additions require permits and must meet Lake Oswego zoning and building codes; Lamont Bros. Design & Construction handles permitting, drawings, and coordination with local authorities.

Is a second story addition a good option for my property?

Second-story additions are ideal for maximizing space on smaller lots, though they involve more structural engineering and cost; Lamont Bros. Design & Construction evaluates feasibility, structure, and budget to determine if it’s the right approach.

Read more: Second-Story Additions: What to Consider Before You Get Started

Why hire a design-build contractor for a home addition?

A design-build contractor unifies design, budgeting, and construction under one team, reducing risk and misalignment; Lamont Bros. Design & Construction delivers a cohesive process that improves accuracy, communication, and final results.

The Lamont Bros. Difference

Award Winning Craftsmanship

Lamont Bros. has earned recognition as a multi-award-winning Portland design-build firm, including the NARI Remodeler of the Year award and Houzz Best Service every year since 2016.

Client-Verified Excellence

Lamont Bros. maintains a 4.8-star average rating across Google, Houzz, and Yelp, reflecting consistent client satisfaction across hundreds of completed remodeling projects.

20 Years of Experience

Since 2008, Lamont Bros. has completed 850+ remodeling projects across the Portland metro area, including kitchens, bathrooms, additions, and ADUs in Portland, Beaverton, Lake Oswego, West Linn, and Oregon City.