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We build all types of additions, from mother-in-law suites to DADUs.

Let's add more space. Whether you're looking to build up or out, our construction experts will ensure your new addition is structurally sound and blends seamlessly with your existing home.

Featured home additions

Need some inspiration? Check out some of our most recent projects — and start gathering ideas for your new addition.
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Local roots, national reach

We're a licensed general contractor with local teams across Seattle, Denver, and the San Francisco Bay Area.

Addition costs 

Generally, the cost of an addition ranges anywhere from $175 to $500+ per square foot. Of course, all projects are different. Even the price of two very similar additions on the same street might be vastly different based on the age of the home or the land underneath. Every situation is unique, but we’re happy to discuss these factors in greater depth. After a free, in-home consultation, we can build a custom estimate that gives you a clear view of the costs of your project. 

If you're not quite ready to get a quote, we recommend exploring localized cost data reports. The Remodeling 2020 Cost vs. Value Report includes the average costs for two example addition projects, comparing the price and scope of a mid-range master suite versus an upscale master suite. Just keep in mind that these examples are national averages and cost varies between cities:

Mid-range master suite addition 

Average cost: $137,000

Project scope: Add a 24x16-foot master bedroom suite over crawlspace. Include walk-in closet/dressing area, freestanding soaker tub, separate 3x4-foot ceramic tile shower, and double-bowl vanity with solid-surface countertop. Carpet the bedroom floor; put tile in bath. Paint walls, ceiling, and trim. Install general and spot lighting, exhaust fan.

Upscale master suite addition 

Average cost: $282,000

Project scope: Add a 32x20-foot master bedroom suite over crawlspace. Add spacious sleeping area with lounging/sitting area adjacent to large master bath. Include custom bookcases and built-in storage with millwork details; high-end gas fireplace with stone hearth and custom mantle; and walk-in closet/dressing area with natural light, mirrors, and linen storage. Add French doors. Bathroom includes walk-in shower with 2019 dual-shower system, stone walls and floor, and custom frameless glass enclosure. Add freestanding soaker tub. Include two sinks in separate custom vanities with stone countertops and large mirrors. Create partitioned area for luxury one-piece toilet. Outside the bath, add 5-foot-long hospitality center with bar sink, undercounter refrigerator, custom cabinetry, stone countertop, and microwave. Include soundproofing, in-floor heating, custom wall finishes and hardware, general and spot lighting, and high-end lighting controls.

© 2020 Hanley Wood, LLC. Complete data from the Remodeling 2019 Cost vs. Value Report can be downloaded free at

Financing options

The loan that’s best for your remodel depends on a lot of personal factors. Did you purchase your home when interest rates were higher? How much of your mortgage have you already paid off? Are you looking at a one-time expense or an ongoing project?

In general, most experts recommend a cash-out refinance, home equity loan, or HELOC for financing a home remodel. But if you’re thinking about purchasing a fixer-upper, we recommend looking into an FHA 203(k). For more information, read our complete guide to financing a home improvement project

Home addition FAQ

What does it take to build an addition?

In terms of the process, building an addition is not unlike building a new house. It requires project management, design, permits, and various subcontractors to build a new structure. Here is a rough overview of what to expect once you've hired your team: 

  • Pull permits 
  • Prepare the site 
  • Build the foundation 
  • Frame the structure 
  • Add sheathing and roofing
  • Install windows and doors
  • Rough-in electrical, plumbing, and HVAC
  • Add insulation and drywall 
  • Finish the interior 
  • Connect plumbing, electrical and HVAC 
  • Complete the punch list

Do I need to hire an architect to build an addition?

Yes. Major structural changes require guidance from an architect. We partner with local firms and independent architects with a strong history of client-centered design. We’ll team up with an architect whose personality, pricing, and style align with yours.

As your architect drafts the plans, we advocate from cost-savings and building efficiency. During construction, they help ensure that the build looks exactly as you intended. Together, we build a space that captures your vision and fits your budget. 

I’ve already hired an architect, can build my addition?

Yes! Many clients come to us with plans in hand. In these cases, we can produce a highly detailed estimate based on the information your architect has provided. We’re also happy to work with your architect to identify ways to make construction more efficient and affordable. 

How do I get started?

We’re excited to meet you wherever you’re at in the process. Some clients come to us ready to build with plans and permits. Others just have a vision and a budget. No matter what you’re considering, we’d be happy to get to know you and your project goals.