How Much Does a Home Addition Cost in Portland?

As a homeowner in the Portland area, you’re beginning to outgrow your home. For one reason or another, there isn’t enough space to live life the way you want to, and you find yourself needing more. However, rather than move to a larger house while house prices and interest rates are on the rise, you want to know how much it will cost to build an addition to your Portland home.

Having built dozens of home addition projects across the Portland area, our team at Lamont Bros. has years of experience in budgeting the cost of adding on to a home.  We’ve worked with many Portland homeowners to design and build for them an addition that meets their needs at a cost that fits their budget. If you want to know how much your addition could cost, you’re in the right place.

In this article, you can read about the cost to build a home addition in the Portland area. Once you’re done reading through it, you’ll have a better idea of what type of addition how much you can expect to pay, and how to keep those costs under control. The specific topics we’ll include are:

What are the Different Categories of Home Additions?

Estimating the cost of a home addition can be difficult because there are so many factors to consider. Additions range in size, complexity, and purpose, and each of these affects its total cost. To make the cost of home additions easier to understand, we’ve broken them down into 3 distinct categories:

  • Simple Home Addition
  • Standard Home Addition
  • Complex Home Addition

Each of these options requires a different scope of work and falls into a different price range. As a general rule of thumb, the more complex an addition is, the more expensive it will be. The prices given below are based on a 500-square-foot floor plan.

Simple Addition — $150,000 – $250,000

As the lowest cost option, a simple addition will also have the most limited scope. An addition in this category would involve adding only living space to the home, such as a bedroom, office, or family room. Essentially, it’s an addition with four walls and a roof that is easy to design and construct.

Simple additions can be thought of as “best-case scenario” projects with no major challenges or issues. The land lot must be level and require minimal excavation. To avoid excessive engineering and design costs, the shape of the addition must be rectangular and follow standard structural principles.

A single-level bedroom addition built on the side of the home with a crawl space foundation is a good example of this type of project.

Standard Addition — $300,000 – $500,000

With almost any addition project, you can expect to run into at least a few challenges during the process. That’s why most home addition projects fall into the category of a standard addition. These types of addition projects are still relatively simple in scope but may involve a few features and challenges that make it more difficult to design or construct. A standard addition may add extra living space or utility space, such as a bathroom, kitchen, or laundry room.

Standard additions often require more engineering and may involve a more complicated construction process. For example, a second-story addition, which adds space on top of an existing level, must go through extensive structural engineering to be approved. Then, the structure of the existing home must be reinforced to support the added weight. Challenges that require extra steps in the design and construction processes add to the cost of the project.

Second-story additions, additions with custom bathrooms or kitchens, and additions built on a steeply-sloped land lot would all fall into the category of standard additions.

Complex Addition — $500,000 – $800,000+

In the case that your addition requires extensive engineering or specialized construction throughout the design, that would qualify as a complex addition. This category of additions is reserved for projects that are exceptionally complicated in scope and design features.

An addition may fall into this category for several reasons. It may be because the planned addition drastically changes the structure of the existing home. Or maybe it’s because the addition is exceptionally large or complicated, requiring new plumbing, electrical, and HVAC systems throughout. It may also be that the project falls into a niche architectural or interior design style that involves specialized construction work to complete.

Additions on historic homes, multi-level additions, and additions that function as accessory dwelling units (ADUs) may fit into this category.

How Much Does the Average Home Addition Cost?

In 2022, our average cost to build a home addition in Portland was $382,000. The least expensive addition we built was a 180 sq. ft. bedroom addition for $171,000. Our most expensive addition project was a 1,400 sq. ft. addition with a garage, bedroom, and hobby room for $576,000.

The type of builder you hire to build a home addition will also have an impact on your total bill. As a design-build firm, Lamont Bros. is a full-service remodeling company. A general contractor, handyman, independent designers, and artisan all have different cost structures, advantages, and disadvantages. Each client and each home addition are unique and you need to determine what the best approach for you is. Read this article on when a design/build firm is and is not a good fit to help you make that decision.

Average Addition Cost — $382,000
Lowest Addition Cost — $171,000
Highest Addition Cost — $576,000

Lamont Bros. Project Data

Where Does the Money Go When Building Home Addition?

Many Portland homeowners want to know how their money is being spent when making a high-cost purchase like a home addition. To better understand what factors influence the total cost of a home addition project, read the breakdown below.


The exterior envelope includes all of the components that keep your home safe from the elements. This includes the sheathing, roofing, weather-resistant barrier, siding, windows, and doors. Materials for these components can vary widely in price, and the complexity of the design can impact cost as well.


19%Interior finishes refer to the materials and features that make up the visible features and surfaces in your home. It’s what makes your addition beautiful and functional and includes flooring, cabinetry, trim, and light fixtures. High-end finishes like marble countertops and custom cabinetry can drive up the overall cost of your project.


Framing is the structural skeleton of your home, supporting walls, floors, and the roof. Constructing the frame is a labor-intensive job that requires significant skill. Both Interior and exterior finishes as well as long-term durability are impacted by the quality of the framing. Costs for framing can vary based on the complexity of the design, the size of the structure, and the amount of materials required.


Electrical, plumbing, and HVAC (heating, ventilation, and air conditioning) are all essential components of your addition’s functionality. These systems require specialized knowledge and experience to install correctly. Builders will typically subcontract this work to licensed professionals.


Excavation and foundation work are critical to the stability of your home. This includes leveling the ground, pouring the foundation, and installing footings. The cost of excavation and foundation work can vary depending on the size and complexity of your project, as well as the soil and topography of your site.


Insulation, drywall, and paint are necessary components of making sure your home is safe, energy-efficient, and beautiful. The cost of these items can depend on the size and design of your home, as well as the quality of materials you choose.


Preparation, management, and cleanup costs include tasks like obtaining permits, hiring a project manager, and cleaning up the job site. These costs may not be as obvious as materials or labor, but they are essential to ensuring that your project is completed safely, efficiently, and within budget.


Design costs refer to the services of architects, designers, and other professionals who help plan and execute your project. The complexity and customization of your design can impact the overall cost of your project. For example, a highly customized design requires additional design hours on the plan set, resulting in higher costs.

What Can Increase the Cost of My Addition?

To be mindful of the total cost of your addition, it’s often helpful to understand what processes and features can increase the price. Here are 3 of the most common.

1. Highly Custom Work

A home addition with a high amount of custom work can add value and personality to a home addition project. However, it can also significantly drive up the overall cost. Custom work often requires higher-quality building materials and more labor to complete. It will take even a skilled craftsman longer to do custom construction work than it will for them to do something more standardized. Additionally, custom features may require unique or hard-to-find materials, many of which are made-to-order and come with a premium upcharge.

For these reasons, it’s important to consider the costs and benefits of custom work when planning a home addition project, especially when there are more standard, readily available options.

Custom work can add character and uniqueness to your home, but it comes at a much higher cost.

2. High-End Finishes & Materials

When planning a home addition project, choosing luxury-level fixtures and materials can quickly drive up your total cost. For example, adding features such as a top-of-the-line kitchen, luxury hardwood flooring, or a fully custom bathroom can increase your project cost by tens or even hundreds of thousands of dollars. While it may be tempting to include all the latest high-end features, it’s important to consider whether they are necessary for your needs and fit into your budget.

It’s important to find materials that are high quality while still maintaining a reasonable price for your project. To do this, it’s best to identify where you are and are not comfortable paying for high-end products in your remodel. Prioritize the features and finishes that are important to you. Ultimately, the goal is to create a home addition that is both functional and beautiful, without overspending on unnecessary features.

3. Over-Building

Sometimes, homeowners will build an addition that exceeds the size of what they need. Building a larger addition than necessary can significantly increase construction costs because it requires more materials and labor.

An overbuilt addition can also result in higher ongoing maintenance and utility costs. A larger addition will require more heating, cooling, and lighting, which can lead to higher energy bills. Additionally, larger spaces often require more cleaning and upkeep, which can further add to the ongoing maintenance costs of the addition.

This is why it’s important to be intentional about assessing your current home and building only what you need. That way, you can avoid unnecessary expenses and keep the project within your budget.

How Can You Save Money on a Home Addition?

If you’re financially cautious but still want to build an addition, there are plenty of ways to save money during the project. Here’s how our team recommends saving money on an addition.

1. Work With a Designer

Working with a designer can be a great way to save time and money on a home addition project. Instead of struggling to come up with solutions to problems on your own, a professional can help you weigh your options and offer creative solutions you may not have considered.

By enlisting the help of a designer, you can also avoid costly design mistakes and find affordable materials that align with your vision and budget.

Working with a professional design team can help ease the homeowner’s burden.

2. Prioritize Your Goals for the Project

One important thing you can do early on is to create a list of needs, wants, and luxuries.

“Needs” are essential features that are necessary for the addition to function properly, such as a bedroom or bathroom. “Wants” are features that you desire, but are not essential, such as a walk-in closet or a fireplace. “Luxuries” are high-end features that would be nice to have, but can be excluded from the design, such as a freestanding tub or a kegerator.

Creating this list is helpful when planning a home addition because it allows you to identify your priorities and make informed decisions about where to allocate your budget.

3. Be Flexible With Plans & Expectations

Everyone has a vision for their ideal home, but not everyone’s budget can accommodate all of their goals. To create a successful home addition project, it’s important to listen to your designers and remain open-minded and flexible to different ideas and solutions.

Value engineering a home addition project often involves a trade-off between cost and desired features. For instance, if you want to add an extra bedroom but also desire a larger living room, you may have to decide which is more important for your needs and budget. By carefully assessing your needs and prioritizing your goals, you can make informed decisions about which features to include in your addition project.

Ready to Talk with an Expert About Your Addition Project?

Now that you’ve educated yourself on the cost of home addition projects, do you have a better idea of how much it would cost to add to your Portland home? If so, continue your research! To learn more about home additions, check out our Additions Resource Page, where you can read more articles and guides from construction professionals on designing and building home additions.

Think you’re ready to start the ball rolling on your home addition? If so, click the button below to schedule a free design consultation with a member of our team. We’ll help you navigate all the tricky parts of building your home addition so you never have to face a challenge alone.