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Home Addition Cost in Washington, D.C. [2025 Data]
Normal Range: $39,053 - $121,601
A home addition costs an average of $80,163 in Washington, D.C. Depending on the location, size, type, and materials, most homeowners spend between $39,053 and $121,601.
How we get this data
Ursula Page / Adobe Stock Photography
Ursula Page / Adobe Stock Photography
Highlights
Building an addition can add valuable living space to your Washington, D.C., home.
Because of D.C.’s small lot sizes, building up with an additional floor may be a better option than building out at ground level.
Home addition costs are based on the size and type of addition, material costs, and more.
Building a home addition in Washington, D.C. can yield an average ROI of 20% to 50%.
The higher cost of living in Washington, D.C., means homeowners will need to budget more for a home addition. The cost of a home addition in Washington, D.C., averages about $80,163, with most homeowners paying between $39,053 and $121,601. We break down some of the factors that contribute to the cost of a home addition so you can budget accordingly for this major project.
Home Addition Cost Factors
Depending on your ideas for your home addition, you’ll need to know about various factors that affect how much you should budget. The addition size and type, the materials you choose, site prep costs, and permit fees can all influence your total project cost. Take a look at how to work these factors into your budget.
Size
Home additions cost between $100 and $300 per square foot if you’re building out and between $400 and $800 per square foot if you’re building up. The cost to add a 10x10 room to a house costs an average of about $20,000 if you build out and around $60,000 if you build up. Where in those ranges your total falls also depends on the complexity of the room and its finishes. For example, adding a bathroom will often cost more than a bedroom since it requires additional plumbing and electrical work. The square footage can also affect how long your home addition takes to build, which may increase your labor costs for larger projects.
Price Notice
Remember that if you add square footage to your home, the cost of your homeowners insurance will increase accordingly. Before you embark on this project, speak to your insurance company about expected costs.
The average lot size in Washington, D.C., is around 2600 square feet, meaning there’s less room for bump-out builds at ground level. In many parts of the city, building up with an additional story is the only way to gain square footage.
| Addition Size (Sq. Ft.) | Bump-Out Build | Second Story Build |
|---|---|---|
| 60 | $7,500–$18,850 | $28,250–$47,100 |
| 80 | $10,050–$25,125 | $37,675–$62,800 |
| 100 | $12,550–$31,400 | $47,100–$78,500 |
| 150 | $18,825–$47,100 | $70,650–$117,750 |
| 200 | $25,100–$62,800 | $94,200–$157,000 |
| 300 | $37,650–$94,200 | $141,300–$235,500 |
| 400 | $50,200–$125,600 | $188,400–$314,000 |
Materials
As you can imagine, it takes many kinds of building materials to complete a custom home addition. Material prices vary widely, so your price could push closer to $121,601 if you choose luxury or high-end materials at each step of the way.
Framing Materials Cost:
| Framing Material | Average Cost per Sq. Ft. | Pros | Cons |
|---|---|---|---|
| Wood | $1–$5 | Cost-effective, easy to install | Fire risk, prone to pests and moisture problems |
| Steel | $2–$4 | Durable, fire-resistant | Complex installation, limits roof design |
Insulation Materials Cost:
| Insulation Material | Average Cost per Sq. Ft. | Pros | Cons |
|---|---|---|---|
| Blown-in | $0.50–$2.30 | Low-cost, fast installation | Prone to water damage, less durable |
| Fiberglass | $0.30–$1.50 | Fire-resistant, cost-effective | Lower R-value, easily damaged |
| Spray foam | $1.50–$4.90 | High R-value, resists pests and moisture | Higher cost, more flammable |
| Rockwool | $1.10–$3.10 | Durable, high R-value | Loose fibers can be a health risk, higher cost |
Roofing Materials Cost:
| Roofing Material | Average Cost per Sq. Ft. | Pros | Cons |
|---|---|---|---|
| Asphalt shingles | $1–$1.20 | Affordable, easy to install | Prone to granule loss, shorter lifespan |
| Metal | $5–$16 | Long lifespan, low-maintenance | Higher cost, difficult to repair |
| Slate | $10–$30 | Longest lifespan, high-end aesthetics | Very heavy, difficult to install/repair |
| Synthetic | $5–$12 | Durable, lightweight | Variable quality, may look engineered |
Flooring Materials Cost:
| Flooring Material | Average Cost per Sq. Ft. | Pros | Cons |
|---|---|---|---|
| Hardwood | $6–$12 | Long-lasting, many available options | Higher cost, prone to dents and scratches |
| Laminate | $1.30–$6 | Budget-friendly, easy to install | Difficult to repair, prone to water damage |
| Tile | $5–$40 | Variety of options, easy to clean | More expensive, complex installation |
| Carpet | $3.50–$11 | Retains warmth, soft to walk on | Difficult to keep clean absorbs odors |
Siding Materials Cost
| Siding Material | Average Cost per Sq. Ft. | Pros | Cons |
|---|---|---|---|
| Vinyl | $3–$12 | Budget-friendly, easy to install | Shorter lifespan, prone to impact damage |
| Fiber cement | $5–$14 | Extremely durable, long lifespan | Higher cost, difficult to repair |
| Wood | $2–$6 | Eco-friendly, wide range of styles | Prone to rot and pest damage, high-maintenance |
Type
The cost to add on a room varies based on the type and size of the room you’re building. Rooms like kitchens and bathrooms require plumbing work that a bedroom doesn’t, while an unfinished attic home addition may not require electrical or HVAC work that a bedroom needs. The cost per square foot for your home addition will vary based on utilities and the finishes required for how you plan on using the extra square footage.
| Addition Type | Average Cost Range |
|---|---|
| Attic | $62,800–$72,200 |
| Bathroom | $54,950–$63,200 |
| Bedroom | $98,125–$112,850 |
| Dining room | $47,100–$54,175 |
| Kitchen | $86,350–$99,300 |
| Laundry room | $12,550–$14,450 |
| Living room | $47,100–$54,175 |
| Mudroom | $18,850–$21,650 |
| Sunroom | $73,800–$84,780 |
| Detached garage | $41,450–$47,725 |
| In-law suite | $129,900–$149,500 |
| Second story | $274,750–$315,575 |
Site Prep
On average, site prep for a home addition costs between $1,500 and $5,000. You may not need any site prep in some cases, while other home addition projects may require grading land, demolishing concrete patios, removing trees, and other work that can add to your total.
Permits
Before beginning construction, you’ll need a permit for your addition from the D.C. Department of Buildings. The permit fee is based on the total cost and scope of your project, and you may need additional permits and inspections if your home is listed as historic, which many D.C. homes are.
Confirm with your contractor that all necessary permits have been pulled and fees have been paid before starting work. Failure to obtain a permit can lead to fees, citations, or having to remove the unpermitted work.
Home Addition Pro Costs
Homebuilder Pro Costs
The cost to hire a general contractor or homebuilder in Washington, D.C., averages 10% to 20% of your project cost, and total labor costs will account for 40% to 60% of the project cost. A qualified general contractor or homebuilder will coordinate your construction, keep the project on schedule and budget, answer your home addition questions, and ensure the project is up to code.
Additional Pros to Consider Hiring
Building an addition requires work from various pros, from electricians and plumbers to run utilities to the new space, to carpenters and interior painters to finish the interior. A structural engineer is a must-have for any home addition project to ensure your plans are structurally sound and compliant with all Washington, D.C., building codes.
Interior painter cost: $2–$6 per sq. ft.
Roofer cost: $4–$11 per sq. ft.
Electrician cost: $50–$100 per hour
HVAC technician cost: $100–$250 per hour
Plumber cost: $45–$200 per hour
Carpenter cost: $75–$125 per hour
Structural engineer cost: $200–$1,500
Landscaper cost: $1,200–$6,200
Does a Home Addition Increase Property Value?
A home addition can add value to your house, especially in Washington, D.C., where space is at a premium. Additions offer a return on investment (ROI) of 20% to 50%, depending on the type of addition, and a new primary suite, expanded kitchen, or additional bathroom can set your home apart from similar properties when it comes time to sell.
How Angi Gets Its Cost Data
Home is the most important place on earth, which is why Angi has helped more than 150 million homeowners transform their houses into homes they adore. To help homeowners with their next project, Angi provides readers with the most accurate cost data and upholds strict editorial standards. We survey real Angi customers about their project costs to develop the pricing data you see, so you can make the best decisions for you and your home. We pair this data with research from reputable sources, including the U.S. Bureau of Labor Statistics, academic journals, market studies, and interviews with industry experts—all to ensure our prices reflect real-world projects.
Want to help us improve our cost data? Send us a recent project quote to [email protected]. Quotes and personal information will not be shared publicly.
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