How much does it cost to add a dormer?
Ashburn, VA

How much does it cost to add a dormer?

Ashburn, VA

How much does it cost to add a dormer?

$90 – $150cost per square foot installed
$3,000 – $25,000average total cost to install

Get free estimates for your project or view our cost guide below:

$90 – $150 cost per square foot installed

$3,000 – $25,000 average total cost to install


Get free estimates for your project or view our cost guide below:
Jennifer Carlson
Written by
Jennifer Carlson
Edited by
Kristen Cramer
Fact-checked by
Tom Grupa

Dormer cost

The cost to add a dormer to a roof or attic is $90 to $150 per square foot or $3,000 to $25,000 on average. Building a shed dormer costs $75 to $120 per square foot, including labor and materials. Fitting a dormer window costs $2,400 to $6,600 with installation.

Cost to add a dormer - chart
Cost to add a dormer - chart
Average cost to add a dormer
Dormer size (square feet) Average cost installed
28 $2,500 – $4,200
40 $3,600 – $6,000
64 $5,800 – $9,600
100 $9,000 – $15,000
200 $18,000 – $30,000
250 $22,500 – $37,500

Dormer cost calculator

The following table shows the average cost to install or replace a dormer.

Average dormer cost calculator
National Average Cost $13,700
Minimum Cost $1,000
Maximum Cost $75,600
Average Range $3,000 to $25,000

Cost to add a dormer by roof type

A dormer costs $65 to $300 per square foot installed, depending on the style. Gable and shed dormers are the most popular dormer style. Hipped, arched, eyebrow, and barrel dormers are more complex and expensive options.

Cost to add a dormer by roof type
Type Cost per square foot
Gable / flared dormer $110 – $150
Shed dormer $75 – $120
Wall roof dormer $75 – $115
Flat roof dormer $80 – $125
Hip dormer $110 – $140
Recessed or inset roof dormer $70 – $150
Eyebrow dormer $100 – $160
Arch / barrel dormer $100 – $150
Pedimented roof dormer $165 – $300
Faux / false / prefab dormer $65 – $90

Dormer roof addition
Dormer roof addition

Cost to add a shed dormer

A shed dormer costs $75 to $120 per square foot installed. The roof of a shed dormer is flat and slightly sloped, which reduces the construction price. This dormer type is known for maximizing square footage.

A wall roof dormer costs $75 to $115 per square foot installed and is a type of shed dormer. The front of a wall dormer blends into the exterior wall of a home instead of being set in the middle of the roof's slope.

Gable dormer cost

A gable dormer costs $110 to $150 per square foot installed and is the most popular dormer type. Gable dormers are triangular with peaked roofs, which shed water and snow easily. Flared gables extend farther out from the house, providing more shade.

A Nantucket dormer, popular in Northeastern states, is made by connecting two gable dormers with a shed dormer.

Flat roof dormer cost

A flat roof dormer costs $80 to $125 per square foot installed. This dormer type may leak more easily and is typically not considered as attractive as other types, but it is simpler and cheaper to build.

Hip roof dormer installation prices

A hipped dormer costs $110 to $140 per square foot installed and has a pyramid-like appearance, with three sloping sides instead of two.

Recessed or inset roof dormer prices

A recessed or inset roof dormer costs $70 to $150 per square foot installed. This dormer style is set into the roof instead of projecting from it. A recessed dormer requires less material to build but adds less square footage and increases the risk of leaking.

Faux and prefab dormer costs

A faux dormer costs $65 to $90 per square foot installed or $2,800 to $8,900 total. A faux dormer–also called a blind or prefabricated dormer–is attached to the home’s exterior instead of penetrating the roof, which reduces construction costs. However, a faux dormer offers no light, air, or space.

Arched top or barrel roof dormer cost

An arched dormer costs $100 to $150 per square foot installed. An arched or barrel dormer has a rounded top and is typically smaller than other dormer types.

Eyebrow dormer addition cost

An eyebrow dormer costs $100 to $160 per square foot installed. This dormer type is small, rounded, and blends into the roof. Eyebrow dormers offer curb appeal but add less light and space than other dormers.

Pedimented roof dormer addition cost

A pedimented roof dormer costs $165 to $300 per square foot installed and is a type of gable dormer. Pedimented dormers have a classical triangular accent above the window. This style is often used in doorways, where the dormer extends out from the roof and is supported by pillars.

Cost to build a dormer on an existing roof

Building a dormer on an existing roof costs $2,400 to $54,900, depending on the type.

Cost to build a dormer by location
Location / type Cost to build
Window dormer $2,400 – $6,600
Attic dormer $19,600 – $54,900
Dormer bathroom $20,600 – $44,400

Dormer window installation cost

Dormer window installation costs $2,400 to $6,600, including labor and materials. These windows add natural light and ventilation to a room. Window dormers cost less to build than full dormers but do not add as much space.

Window replacement costs may be necessary after 20 years or significant damage.

Attic dormer addition cost

An attic dormer addition costs $19,600 to $54,900, depending on the size and scope of the project. Shed and gable dormers are the most popular option when turning an attic into a living space. An attic renovation costs $15,000 to $85,000 total on average.

Cost to add a dormer bathroom

A dormer bathroom addition costs $20,600 to $44,400 with installation. Dormer bathrooms often cost more than other dormer types because of the added plumbing, material, and labor required.

A new bathroom costs $4,500 and $12,400, depending on material quality and whether it's a half or full bath. Remodeling an existing bathroom costs $2,000 to $5,000 for a small half bath or $4,200 to $9,600 for a 5x7 full bath.

Cost to add a dormer to a Cape Cod, bungalow, or ranch house

Adding a dormer to a Cape Cod, bungalow, or ranch house costs $110 to $150 per square foot, including labor and materials. Most homeowners prefer gable dormers for these house types.

Dormer conversion cost factors

The following factors affect the cost to install a dormer:

  • Size and shape – Installing a single small or faux dormer window costs less than multiple dormer windows, a bathroom dormer, or an attic extension.

  • Roof slope – Flat roof dormers cost less than steep dormers.

  • Roof type – An existing roof with premium materials costs more to match than asphalt shingles.

  • Labor costs / General contractor General contractors charge $50 to $150 per hour or 10% to 20% of the total construction budget.

  • Framing / Reinforcement – New roof framing costs $5 to $14 per square foot for trusses or $7 to $30 per square foot for rafters.

  • Reinforcements – A steel beam costs $100 to $400 per foot installed or $1,200 and $4,200 on average. A structural engineer may recommend a beam to support the added weight of a large dormer.

  • Structural engineer Structural engineers charge $100 to $220 per hour or 1% to 5% of the total construction cost to ensure the changes will not harm the home's structural integrity.

  • Architect cost Architects charge $100 to $250 per hour or $2 to $15 per square foot to create a home design plan featuring dormers.

  • Blueprints – Residential blueprints cost $0.35 to $5.00 per square foot or $30 to $120 per hour. A draftsperson creates the blueprint after the architect completes the design.

  • Interior work – Drywall, insulation, wiring, painting, or other finishing work impact the final cost.

  • Permits – Building permits cost $50 to $200 for windows. Larger room and bathroom renovation permits cost $200 to $800.

Cost to remove dormers

The cost to remove dormers depends on the size and material. Contractors typically do not recommend removing dormers unless they are being replaced.

Dormer cladding cost

Dormer cladding or siding costs $3 to $13 per square foot installed or $1 to $14 per square foot for materials. Vinyl, aluminum, wood, and fiber cement siding cost the least, while brick and stone are more expensive. Cladding protects dormer walls from moisture and severe weather.

Pros and cons of putting in a roof dormer

Dormers add light, airflow, and living space to a home while increasing its value and aesthetic appeal. However, dormers are also expensive and may be vulnerable to leaks if not installed properly.

Dormer pros and cons
Pros Cons
  • Curb appeal
  • Added light
  • More ventilation
  • Increased square footage
  • Extra emergency exit
  • High return on investment (ROI)
  • Costly
  • Time-consuming installation
  • Susceptible to leaks

What is a dormer?

A dormer is a smaller roofed structure that projects from a sloped roof and contains one or more windows. A dormer's roof may be peaked, arched, flat, or hipped and typically matches the rest of the home's roof material and style. Dormers add space to a room, bathroom, or attic.

What is a full dormer?

A full dormer is an extension of a whole room or floor of a house. Shed dormers are most often used for this project.

How long does it take to build a dormer?

Small window dormers take 1 day to 1 week to install. Larger dormer projects take 1 to 6 months, depending on the style, size, permits needed, and amount of interior renovation.

How much square footage does a dormer add?

A dormer adds 25 to 250 square feet to a home, depending on the dormer type and renovation size. Faux and eyebrow dormers typically do not add space.

How big can a dormer be?

Dormers can be as small as a single window or as large as a floor of a house.

Do dormers add value to a house?

Dormers add value to a home by adding space, light, and curb appeal. The return on investment (ROI) for dormers is 40% to 60% on average.

Do you need a permit for a dormer window?

Installing a dormer window typically requires a permit and may require HOA approval. Verify local laws and HOA regulations before beginning a project.

Getting estimates from dormer addition contractors

Before hiring a home addition contractor or general contractor near you to add a dormer, be sure to:

  • Get three or more quotes to compare.

  • Read their reviews on HomeGuide and Google.

  • Look for companies with a state contractor license.

  • Select a certified, insured, bonded company with 5+ years’ experience.

  • Verify that the contractor has experience with your roof type.

  • Ask for a clear written estimate and warranty before work begins.

  • Avoid large upfront payments. Instead, negotiate a payment schedule and save receipts.

Questions to ask

  • How long have you been in business?

  • Are you licensed, insured, and bonded?

  • Can you provide references for past work?

  • What certifications do you have?

  • Can you provide a detailed quote?

  • Does your quote include waste disposal or taxes?

  • How long will the project take?

  • Which dormer style do you recommend for my house?

  • How will you access my roof? What safety precautions will you take?

  • What additional fees may be required?

  • Do you offer financing?

  • Will you obtain any necessary permits?