Top 10 Roof Dormer Types, Plus Costs and Pros & Cons

Roof dormers can improve architectural design of your home, add living space, and provide other benefits, but what are your options? How much does a roof dormer cost?

This guide covers major dormer types and how much they cost to build. Before we delve into various dormer types, let’s quickly explore feasibility considerations and pros and cons of building a dormer:

Feasibility Considerations

Question: Is a roof dormer even feasible for your property?

Answer: It depends on the type of your roof frame; A stick-framed roof with an attic has room for adding a dormer, while a truss-framed roof doesn’t have any attic space to add a dormer to. You can still add a purely decorative make-believe dormer to a truss-framed roof, but not a real dormer.

The Pros

There are several good reasons for a roof dormer:

Dormers add architectural interest, accent, and detail: Having one or more dormers as part of a roof’s structure can boost the curb appeal of a home that might otherwise be a bit bland. The new design features can look good inside too. You’ll enjoy the improved aesthetics of your home, and the upgrade will make it more appealing to buyers, if you decide to put it up for sale. Dormers have an average return on investment or recouped value of 65-70 percent.

Roof dormers add light: If the dormer is built above living space rather than over an attic, or if you’re converting attic space to living space, then it provides much-needed natural light. Dormers are wonderful spots for a reading nook, kids play area, dressing area and other uses where extra light is a bonus.

Improved ventilation: Dormers are built in multi-story homes on upper floors where heat rises and air can become stale and stuffy. The dormer window allows for fresh air and better airflow to improve the ventilation and air quality.

More room and headspace: When dormers are large, such as a shed dormer that runs the length of a bungalow, a 1.5-story home, the increase in usable space can make a difference.

A room with a view: In addition to light, the dormer provides another view on the world outside.

Another potential exit: In emergencies, a dormer window provides an exit opportunity. This is especially important if the dormer window is the only exit in an attic roof. If you have a multistory home, a rope or chain ladder should be kept in a handy upstairs location.

The Cons

What should you be aware of before committing to a dormer?

Extra cost: Dormers require additional building materials and time — the inputs that increase the cost of construction. Getting the permit and hiring an architect, if necessary, boost costs not associated with simply tearing off shingles and installing a new set.

The cost will be slightly higher every time the home is reroofed due to additional materials and time requirements.

In 20-30 years, the window within the dormer will have to be replaced, another significant cost.

The best time to limit the cost of a dormer is when the home is being built. In existing homes, it is most cost-effective to add a dormer when a roof is being replaced.

Valleys: Most dormers create valleys on either side, and valleys are notorious for leaks because a higher volume of water runs through them. However, valley flashing materials are designed to prevent leaks, and experienced roofing contractors successfully roof valleys every day.

On our scorecard, dormers are ahead 6 to 2, so we think they’re worth the cost and risk, especially if you would like to add some visual appeal or additional living space to your home.

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Ten Types of Dormers and Their Costs

Here are the most common types of dormer for you to compare along with construction costs for each. As you will see, several dormer styles go by more than one name.

The costs provided in this guide are for the construction of the dormer frame and include average material costs for siding, windows and roofing. Architectural and building permitting costs can further increase your overall costs.

A roofing material you select can be a significant cost factor. For example, a tile roof will cost much more than a roof covered with shingles.

Note: the steeper the roof, the less the roof of the gable will extend out from the roof and the lower the cost of materials will be.

Arched top or barrel roof dormer:

Barrel Roof Dormers
via Custom Copper Works

A rounded top is the hallmark of this dormer type that has some wall space on sides and front. An arched or barrel dormer adds a soft contrast to the sharp, straight lines of most sloped roofs. This dormer type is less commonly called a segmental roof dormer.

  • Use notes: Arched/barrel dormers are usually for light and visual appeal rather than to produce more living space. Consequently, they tend to be smaller than some other styles.
  • Cost notes: A rounded roof takes more time to construct than a flat or gable roof
  • Arched roof dormer cost: $100-$150 per square foot or $4,000 to $6,000 total
  • Average cost and size: $4,650 for dormer 5’ wide x 8’ deep

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