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You can add a dormer to your existing roof for $2,500 to $30,000, or about $115 per square foot. Most homeowners pay $12,000.* Dormers are common on Cape Cod houses and bungalows. These small, roofed structures extend from your roof and often feature a window, increasing your home’s space and boosting curb appeal while bringing in more natural light.
Our guide covers key costs you’ll need to consider when installing a dormer window, plus tips for hiring a professional roofing contractor.
*Article cost data via Home Advisor.
Major Cost Factors for Dormer Addition
The dormer’s size, type, material, and required labor all affect your total cost. We’ll detail these factors below.
Types of Dormers
There are many dormer styles to choose from. Here are some common types of dormers and their costs by square footage.
- Shed dormer ($75 to $120): This large, flat dormer sits atop the roof horizontally. These have a flatter pitch than other dormer types and can add significant attic space.
- Eyelid dormer ($105 to $160): Also known as an eyebrow dormer, this is a smaller, arched window that extends from the roof’s slope. This style adds more light but less space.
- Gable dormer ($110 to $150): Two planes slope in opposite directions, creating a triangle shape. This is the most common type of dormer and often includes one window.
- Hip dormer ($115 to $135): These dormers have three sloping planes to match a hipped roof. They can increase headroom on your home’s top floor but require more roofing materials.
Many different materials are used to build dormers, each of which vary in durability and maintenance requirements. Aluminum and vinyl are the most cost-effective options, but wood is more customizable.
Cost by Material
We’ve broken down the cost of roof dormers by material below.
Labor prices vary by project and roofing contractor. Pros will either charge a flat rate equal to 20% to 30% of the total project cost or an hourly rate; the national average is $35 to $55 per hour. Sometimes, you may need to hire an architect to assist in planning and installation. Architects charge per project; fees are generally 5% to 20% of the total project cost.
Professional vs. DIY Dormer Addition
We recommend hiring a professional roofing company to install your dormer rather than attempting a do-it-yourself (DIY) installation. A pro can get necessary permits, follow building codes, and fix structural issues. We’ll take a closer look at both options below.
Labor costs for a dormer addition are high because the project involves opening the roof and adding weight to it and your home’s foundation. A professional roofer will be able to match the new dormer to your existing roof and inspect it for any issues.
Here are some other benefits of hiring a pro:
- They have the necessary training, tools, and safety equipment.
- They can identify underlying issues that may not be obvious to the average homeowner.
- They can determine if your home can support a dormer’s additional weight.
- They have knowledge of the required building permits for the project.
- They offer manufacturer warranties on materials and guarantees on their work.
- Reputable roofing companies are licensed, bonded, and insured to protect you financially.
Even if you have roofing experience, we don’t recommend a DIY dormer addition. This isn’t a project you can do alone, and one mistake could damage your home’s structural integrity. During installation, your roof may require temporary support structures, and a professional has specialized skills and knowledge to do this safely.
Additional Factors Affecting Dormer Costs
Some additional factors can drive up your total dormer price. Read more about them below.
If your roof can’t support new dormers, you may need to install additional framing, adding $1,000 to $10,000 to the total cost.
Installing a dormer may require other work before the project can begin, such as replacing or repairing framing, siding, roofing, and other finishing work. For example, your roof may need repairs before a dormer can be added. Repairing a roof costs $4 to $9 per square foot, and a full replacement is $5,884 to $12,738 on average.
Other projects include framing ($6 to $9 per square foot) and cladding ($2 to $15 per square foot). Your roof may need trusses for extra support. Roof trusses cost between $7,200 and $12,000.
You usually need a permit to add a dormer to your home. Building permits typically cost $390 to $1,930, with an average cost of $1,160. What you pay depends on local laws. Check with your area’s local planning authority for accurate pricing.
Your roof’s height and slope can increase the installation’s complexity. A higher roof with a steep pitch usually requires more materials, labor, and structural considerations. Roofers may also need specialized equipment to safely access higher areas.
Type of Roof
Your roof type will affect the project cost. Dormers are often added to unfinished attic spaces, typically costing between $75 and $120 per square foot. Installing a bathroom dormer is usually more expensive, as it requires a more extensive renovation. Expect to pay $20,000 to $55,000 for a bathroom dormer.
How to Reduce Costs
There are other ways to save money on your dormer installation besides attempting a risky DIY project. Here are some tips.
- Get multiple quotes: Compare costs and identify contractors who are overcharging or undercharging.
- Choose a minimal size: Opt for a smaller dormer to reduce material and labor costs.
- Use affordable materials: Choose a cost-effective material, such as vinyl, over wood.
- Consider prefab over custom: A prefab dormer is less expensive than a custom one, ranging from $65 to $90 per square foot.
- Install in conjunction with a roof replacement: Contractors often give discounts when you request multiple services. You may be able to save on roof replacement expenses if you install a dormer at the same time.
- Do the finishing work: Do some finishing work yourself, such as painting or adding trim and molding.
How to Hire a Professional
Here are some tips for hiring a professional to install your dormer.
- Get at least three estimates from contractors in your area.
- Ask for references and look at the company’s previous work.
- Make sure the contractor has experience with dormer installation.
- Check out the company on the Better Business Bureau website and read reviews on websites such as Trustpilot and Google Reviews.
- Make sure the contractor you hire is licensed, insured, and bonded.
- Get any cost estimates, guarantees, or warranties in writing.
A dormer can add natural light and extra space to your home. Though the installation cost is high, it’s an investment that can significantly boost your home’s curb appeal. Keep in mind that not all roofs can hold a dormer’s extra weight. A professional roofer can help you identify if you need additional framing or other roof repairs before work can begin.
We recommend getting several quotes from local roofing contractors and comparing their warranty options and installation costs before hiring one.
Cost to Add Dormer FAQ
Do dormers add value to a house?
Yes, dormers add value to a house. The estimated return on investment is around 40%.
Can you add dormers to an existing roof?
Yes, you can add a dormer to an existing roof. Talk with your contractor to see if structural changes on your current roof are possible.
What are dormers?
Dormers are structures that extend from the plane of a sloped roof. These often include a window to allow more natural light into the home. A dormer also has its own roof and siding.