Shed and gable dormers are the two most common choices, and they solve different problems. A shed dormer is a box with a single sloping roof that adds headroom and floor area. A gable dormer has a small pitched roof with a triangular front, which adds charm and light but less usable volume.

What is a shed dormer?

A shed dormer has one flat sloping roof plane, set at a shallower pitch than the main roof. It can run along most of the roof width, which makes it ideal for converting a cramped attic into a bedroom or bathroom. Because the roof framing is simple, labor time is lower.

What is a gable dormer?

A gable dormer, also called a doghouse dormer, has two sloping roof faces that meet at a ridge, finished with a triangular gable above the window. It echoes the lines of traditional houses and works well on front elevations where appearance matters.

Side-by-side comparison

  • Cost: Shed dormers are usually 10 to 25 percent cheaper per square foot because the roof is simpler.
  • Usable space: Shed dormers win. They add near-full ceiling height across their width.
  • Appearance: Gable dormers look more traditional and blend into period homes. Shed dormers look more modern and are often kept to the rear.
  • Complexity: Gable dormers need valleys, flashing and ridge tie-ins that raise labor and leak risk.
  • Light: Both bring in light. A wide shed dormer can hold several windows.
  • Planning: Front gable dormers are more often approved than front shed dormers, which can look boxy.

Which should you choose?

Pick a shed dormer if you need a real room, the dormer faces the back or side, and value matters most. Pick a gable dormer if the dormer faces the street, your home has a traditional style, or you only want a bright window nook. Many homes use both: a wide shed dormer at the rear and a small gable dormer at the front.

How roof pitch changes the result

The pitch of the dormer roof controls headroom and water shedding. A shed dormer roof should never be shallower than about 2:12 for most roofing, and 3:12 to 4:12 is safer for shingles. Gable dormers usually copy the main roof pitch. Try different pitches in the dormer calculator to see how the roof area and cost change. For the geometry behind that, read how to calculate dormer roof area.

Compare both types with your dimensions

Run your width, depth, height and pitch through the calculator and see the cost range for your chosen finish.

Use the dormer calculator

Summary

If you need space, build a shed dormer. If you need curb appeal, build a gable dormer. If you need both, combine them and let each do what it does best.