How Much Does a Dormer Addition Cost in 2024?

Average Dormer Addition Cost

What Is a Dormer?

Dormers are window structures added to roofs—typically a sloped roof—that project vertically beyond the roof to increase useable space, add natural light, and improve the architectural design of your home. The dormer starts from the top floor of the home and has its own roof and siding surrounding the window that matches your preexisting siding. Dormer windows come in various shapes and sizes to match your needs and style preferences.

Can I Add a Dormer?

Before adding a dormer to your roof, you may need to invest in repairs. The area may require upgrades or replacements, particularly to ensure the new dormer material matches the existing roof. Your home's frame and foundation need to be able to support the added weight of the new dormer.

“Depending on a home’s existing roof, the actual roofing material will naturally fade to some degree over time from sun exposure,” says Ezra Laniado, Angi Expert Review Board member and owner of Landmark Construction & Development Group, Inc. “Because of this fading process, you should compare the color of the new dormer against the existing roof. In some cases, you might need to reroof the house while adding the dormer to get a seamless finish.”  

Valleys—which dormers create on either side—are another consideration. Valleys are notorious for leaks because water tends to collect in these areas, often at high volumes, putting stress on the roof. While there are materials local home addition contractors can use to prevent leakage, you’ll want to take additional precautions to be safe.

Evaluate the roof’s age, too. Even if it’s not leaking currently, an older roof will become more leak-prone once you start agitating the waterproofing membrane. 

Dormer Addition Cost Factors

Several components affect the overall cost of adding a dormer. Below, we’ll discuss each of these home addition cost factors in more detail.  

Labor

You might feel tempted to DIY this project, but adding a dormer is best left to a pro. Roofing contractors generally charge a bit more for their specialized knowledge and experience than average general contractor rates. Typically, a professional roofing contractor charges a flat rate—about 20% to 30% of the total project cost or an average hourly rate of $35 to $55 per hour. 

Type of Roof

Roofing costs can vary, so the type of roof you have will factor into the dormer cost. Installing a dormer in a home with an attic generally costs less because it serves as an extension of the space. Attic dormers cost between $75 and $120 per square foot.

Cape Cod houses and bungalows are popular home styles for dormer additions. Gable dormers added to these homes with sloped roofs cost between $110 to $150 per square foot.

Framing

Framing is essential for a dormer addition. The cost to frame a roof ranges from $7 to $16 per square foot. Due to the complexity of the design, adding a dormer will likely fall on the higher end of that range. 

Custom vs. Prefab or Faux

Prefabricated dormers cost between $8,000 and $14,000, not including labor and installation. The price comes from their larger size and the cost associated with building, transporting, and lifting them.

You can purchase faux or “fake” dormers at a home improvement store. It’s more wallet-friendly to go this route, but you won’t reap the ROI benefits or the increase in square footage. 

Prefab or faux dormers are more common with DIY projects. However, this is a challenging roof project, and you should only take it on if you’re an advanced-level DIYer. 

Window Glass

Besides adding extra space, dormers offer more natural light and ventilation with a window install. On average, window dormers cost $4,000 but can range between $3,000 to $8,000. 

Eyebrow dormers and arched-top dormers are typically installed to bring extra light into a room but don’t offer additional space. The cost for these types of dormers is on the lower end of the range, between $3,000 and $4,500.

Reinforcement

Adding a dormer to your home puts extra weight on the frame and foundation. Your roof may require additional support to hold up the material. If so, remodeling and addition costs can add an extra $1,000 to $10,000.  

Engineering

Dormer installation is a big undertaking that requires careful consideration to maintain the sound structure of your home. It’s a good idea to consider hiring an architect to assist you through the process. Architects typically charge per project, and their fees usually fall between 5% and 20% of the total project cost. 

Permits

You’ll likely need planning permission or a permit for a dormer. Generally, a building permit for an addition like a dormer costs between $390 and $1,930, or about $1,160 on average. The true price depends on local laws in your area. Check with your local planning authority, who can help answer permit questions directly.

Cladding

Dormer cladding can cost anywhere from $3 to $15 per square foot. Prices vary based on local material and labor costs, so the actual price may be higher. Cost factors include:

• Type of cladding

• Material removal

• Size of coverage area

Roof Trusses

Depending on your roof, you may need to add roof trusses to accommodate the dormer install. A roof truss is a premade frame that can reduce labor costs and simplify assembly. Roof truss installation costs between $7,200 and $12,000.

Interior Finishing

Adding a dormer also requires interior finishing, especially if you’re opening up a room. You’ll need to factor in the cost of drywall and paint as well as the labor associated with it, if applicable. You can expect to pay between $6 to $9 per square foot. 

Roof Replacement

If you’re choosing between replacing your roof or adding a dormer, roof replacement is the less costly option. The national average cost of roof replacement is typically between $5,700 and $12,000 or between $3.50 and $5 per square foot. 

How to Calculate Dormer Costs

Dormer costs are determined by the dormer style, size, location of installation, and your roof type. Additional cost factors include permits, materials and labor, and interior work such as drywall and painting. 

Your total dormer addition cost will also include any work required before construction, such as applying for permits and determining whether your roof requires repairs or renovations.

Average Cost to Add a Dormer by Roof Type

Below are the costs of various dormer roof types. 

Shed Dormer Costs vs. Gable Dormers

Gable dormers are the most common type of dormer and are typically found on roofs that have a steep pitch and an angle. These dormers are an attractive and cost-effective add-on that can let more light into your home.

Because of their simpler design, shed and flat dormers cost less compared to hipped, eyebrow, and arched dormers. Shed dormers are also more conducive to larger sizes, adding more square footage to smaller homes. 

A combination of a shed and gable dormer is a Nantucket dormer. For this type of upgrade, roofing pros erect two gable dormers and connect them with a shed dormer.

Do Dormers Increase Home Value?

The typical return on investment (ROI) for adding a dormer is around 40%. For example, if adding a dormer costs $10,000, you can expect your home value to increase by about $4,000. You may also save money on electricity bills over the years due to the increase of natural light in your home.

Other remodeling projects, such as adding a deck, finishing your basement, and upgrading your kitchen, can also increase the value of your home.

Budgeting for a Dormer Addition

Adding a dormer to your home can increase living space and natural light, but it can also be a costly undertaking. With some strategic planning and savvy cost-saving decisions, there are ways to keep your dormer addition project within budget while still achieving the desired results.

• Obtain estimates from at least three reputable contractors in your area. Compare prices and reviews to ensure you’re getting a fair deal.

• Choose a simpler dormer design without complex architectural elements and features. This can reduce material and labor costs.

• Select standard-sized, readily available windows for your dormer. Custom windows require custom framing, which adds to your costs.

• If it makes sense, combine your dormer addition project with other projects, like roof replacement.

• Take care of the interior painting task yourself to save on labor costs.

• Design a dormer space that minimizes the need for new electrical or plumbing work.

How HomeAdvisor Gets Its Cost Data

No place is more important than your home, which is why HomeAdvisor connects homeowners with local pros to transform their houses into homes they love. To help homeowners prepare for their next project, HomeAdvisor provides readers with accurate cost data and follows strict editorial guidelines. After a project is complete, we survey real customers about the 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.