How Much Does a Dormer Addition Cost in 2025?
A dormer addition costs an average of $15,000
The overall dormer addition cost can range from $2,500 on the low end to as high as $80,000, with most homeowners spending an average of $15,000.
Factors like construction complexity and material quality significantly impact the final pricing of your dormer addition.
Adding dormers boosts curb appeal, increases natural light, and expands living space.
You’ll also need to budget for permits, roof repairs, and structural reinforcements.
Hiring a professional for your dormer addition ensures code compliance and maintains the structural integrity of your home.
This article was updated using automation technology and thoroughly reviewed for accuracy by HomeAdvisor Editor Ryan Noonan.
Homeowners spend an average of $15,000 on dormer addition costs, with most projects averaging between $6,000 and $25,000. Low-end jobs start near $2,500, while complex builds can reach $80,000. Main cost factors include roof type, framing, reinforcement, and labor. If you plan additional attic upgrades down the road, remember that dormer costs rise each time you open the roof.
What Is a Dormer?
Dormers are window structures added to roofs, often a sloped roof, that project vertically beyond the roof to increase usable 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.
Before starting a dormer addition, make sure the roof is in good shape and the structure can handle extra weight. You may need minor repairs or upgraded shingles so the new dormer blends in. Dormers create roof valleys that collect water, so plan for leak-proof flashing and membranes. A qualified local home addition contractor can recommend the right products and installation steps.
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
The amount you’ll pay for your dormer addition depends on a variety of factors. Here’s a closer look at how your total cost breaks down.
Cost to Add a Dormer by Roof Type
Roofing costs can vary, so the type of roof you have will factor into the dormer cost. Flat dormers cost between $90 and $130 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 and $150 per square foot.
| Dormer Type | Cost per Sq. Ft. |
|---|---|
| Flat | $90–$130 |
| Shed | $80–$120 |
| Gable | $110–$150 |
| Hip | $110–$150 |
| Nantucket | $100–$140 |
| Prefab | $70–$100 |
Shed Dormer Costs vs. Gable Dormers
Gable dormers are the most common type of dormer and are found on roofs with a steep pitch and a pronounced 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 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.
Labor
While a dormer may look DIY-friendly, it’s a pro-level project. Roofing contractors charge a bit more for their specialized knowledge and experience than average general contractor rates. A professional roofing contractor charges a flat rate, between 20% to 30% of the total project cost, or an average of $8,000.
Framing
Framing is essential for a dormer addition. The cost to frame a roof averages $2,000 to $5,000. 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 $70 and $100 per square foot, 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 units show up on many DIY job lists, but building even a ‘simple’ dormer is advanced work—tackle it yourself only if you have serious roofing experience.
Window Glass
Besides adding extra space, dormers offer more natural light and ventilation with a window install. On average, window glass costs $500 to $1,500.
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 $4,000 to $12,000.
Permits
You’ll likely need planning permission or a permit for a dormer. A building permit for an addition like a dormer costs between $400 and $2,000. The actual price depends on local laws in your area. Check with your local planning authority, which can help answer permit questions directly.
Cladding
Dormer cladding can cost anywhere from $2 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
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 strategic planning and savvy cost-saving decisions, it is possible 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.
Handle the interior painting yourself to trim 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.
Frequently Asked Questions
An average dormer adds roughly 100 square feet, but designs can stretch to 250 square feet or more. If you’ve opened adjacent attic space or opted for an oversized build, you could net even greater footage. Consult with your dormer addition pro to discuss your options and to choose a size that works best for your home’s structure.
A dormer’s life span matches the materials you choose. High-quality elements such as slate, clay, or concrete endure for more than a century, while asphalt shingles support a lifespan of about 30 years. The dormer’s structure remains strong with meticulous maintenance, and only components like windows, insulation, and eaves require periodic attention to keep it both functional and attractive.
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