What Is a Dormer? The Most Common Types to Consider

Wondering what to call that window jutting out from your roof? Learn more about dormer windows, including pros, cons, and installation considerations.

Simply put, a dormer is a vertical window that is set on a slanted roof. Prominent in 16th-century European architecture, many American homes feature them. The dormer, also called a dormer window, has its own roof, which could be arched, flat, pointed, or ornate. Because dormers jut out beyond the pitched roof, they add depth and dimension to a home.

A dormer is also a practical source of ventilation that enables airflow and natural light to pass through your home. In older homes, these can be found in walk-in attics or low-clearance top floors. Newer homes can be designed with a false dormer—a purely ornamental feature with no interior space—or strategically placed on a full-size top floor.

small white house exterior
Anthony Masterson

Which Kinds of Houses Have Dormers?

Dormers have been a part of western architecture for centuries. The word is said to have its roots in France, where it was a feature of a sleeping room or bedroom in the attic. English gothic and Catholic churches also have prominent dormers. These days, many single-family or semi-detached homes in the United States have them too. Typically, historic homes built before the mid-1900s have them, but any newly built home can easily have one for style or as part of a loft conversion.

Types of Dormers

While they all serve the same general purpose, there are several different types of dormers to choose from:

  • Arched top
  • Blind/false
  • Eyebrow or eyelid
  • Flared gable
  • Gabled
  • Hipped
  • Lucarne
  • Nantucket
  • Pediment
  • Polygonal
  • Pyramid
  • Recessed
  • Shed
  • Steep roof shed
  • Wall dormer
white home exterior
Emily Followill

Can I Install a Dormer on a House That Doesn't Have One?

If your home is already built but doesn't have a dormer, it may be possible to have a roofing and window specialist install one. First, you'll need to budget around $12,000-$15,000 for the project, which includes labor, roof repairs and reinforcement, new siding, and other structural changes to the attic. Only an experienced roofing contractor should be trusted with the installation of a dormer, but even before that, you may need to get permission from your township or county to have this work done. For those kinds of approvals, often an architectural design and/or engineering report is needed, as this is a major structural change.

An experienced roofing contractor will ensure the valleys along the side of the dormer are water-tight and properly insulated. Flawed dormer design can ruin more than your curb appeal; it can also damage the frame of the home. So, check with a professional for a feasibility analysis before embarking on a DIY journey or buying materials.

Alternatively, consider a faux dormer, which is affixed to the exterior of the roof, but doesn't have any interior components.

Consider that these changes could void existing roof warranties. You'll also need to inform your homeowner's insurance that major repairs are underway.

How to Determine the Cost of Dormer Installation

The cost of the installation of a dormer depends on the project requirements. According to a June 2022 report from HomeAdvisor, the average cost of installing a dormer is $12,000. However, at $115/ square foot, prices range from $2,500 to $30,000 depending on the size, quantity, and design of the dormers. You should get detailed quotes from various contractors to understand both short- and long-term costs.

Factors That Affect Dormer Installation Costs

  • Cost of permits, insurance, and inspections
  • Labor costs and availability
  • Paints, materials, and finishing costs
  • Rubbish removal
  • The size of the dormer and how many you'd like
  • The style of the dormer
  • The type of roof you already have
  • Where you want it installed
pitched roof colonial style home
Edmund Barr

Pros and Cons of Roof Dormers

Pros of Dormers

  • Increased inflow of sunlight
  • Increased ventilation
  • Curb appeal
  • Increased indoor space
  • Differentiates property from others

Cons of Dormers

  • Cannot be installed in all types of houses
  • Requires permission from authorities
  • High installation costs
  • Water and air leakage potential
  • If placed in historical homes, windows and insulation will need upkeep
  • Increased exposure to harsh weather
  • If not sealed well, can be an access point for birds, squirrels, and other pests

What If My Home Already Has a Dormer?

If your home already has a dormer window, you're in luck. You already know the versatility of the design and enjoy the aesthetic appeal it adds to the home. Prioritize care and maintenance by insulating dormer windows, as well as the floors of the loft, bungalow, or attic. This will make the space more functional and ensure that it won't unexpectedly increase heating or cooling costs. Don't forget that drainage and flashing are crucial to the life of the roof. Make sure gutters and downspouts are properly placed. Last, plan to repaint the exterior every few years, as weather can fade exterior paint and damage scalloped or ornate designs.

Frequently Asked Questions

  • What's the difference between a gable and a dormer?

    In its simplest form, a gable is a triangular part of a wall that encloses a pitched roofline, often featuring an ornamental window called a gable window. A dormer is a window (often accompanied by roof and siding) that actually protrudes from a home as a means of adding light and architectural interest.

  • Can you put a dormer over a doorway?

    You can add a dormer over a doorway, though it's not a particularly common look. More often, over-the-door dormer windows are paired with a small portico over the door to balance the look on the exterior of the home.

  • Are all dormers functional?

    No! While it is possible to have an exterior dormer correspond with an interior room and functioning window, there are also "false dormers" added to a home's exterior for purely aesthetic purposes. Many times, it's impossible to distinguish the difference between the two by simply looking at the home.

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