Dormer - Roof Projection and Leak Repair Home Guide

A dormer is a roofed projection built out from a sloped roof, usually to add headroom, usable space, or a window to the upper level of a house.

Dormer diagram — labeled parts, dimensions, and installation context

What It Is

A dormer is both a framing and roofing feature. It interrupts the main roof plane to create a vertical wall area for a window or to expand the usable space inside an attic or upper story.

Because dormers combine roof framing, flashing, siding, windows, and insulation in one compact assembly, they are common trouble spots when details are poor.

Types

Common dormer types include gable dormers, shed dormers, eyebrow dormers, and wall dormers. The roof shape changes the look and the interior space gained.

Where It Is Used

Dormers are used on upper-story roofs, finished attic spaces, bonus rooms, and older homes where expanded headroom and natural light are important.

How to Identify One

A dormer projects outward from the main roof and usually contains its own small roof section and a vertical wall with a window.

Replacement

Dormers are not simple replacement parts, but they often need repair when flashing fails, framing settles, siding rots, or window leaks damage the assembly. Major reconstruction has to treat the dormer as part of the roof system, not just a window opening.

Dormer — FAQ

What does a dormer do on a house?

It adds light, headroom, and usable space by projecting out from the roof. It can also change the look and balance of the home's exterior.

Why do dormers leak so often?

Dormers have multiple joints where roof, wall, flashing, and window details come together. If any of those transitions are weak, water can get in.

Is a dormer structural?

Yes. A dormer involves roof framing changes and has to be integrated into the structural and weatherproofing system of the roof.

Can a dormer be repaired without reroofing the whole house?

Sometimes, especially if the problem is limited to flashing, siding, or a window detail. Broader roof wear can make larger work more practical.