Which feature adds a vertical window through the roof?

• A. Dormer
• B. Oriel
• C. Clearstory
• D. Bay window

Answer: (A)

A dormer is the feature that creates a vertical window through the roof. It’s a small structure that projects from the slope of the roof, adding space beneath and bringing in daylight through a window set in that roof-facing projection. This design choice is commonly used to convert attic or upper-floor space into usable rooms by increasing headroom and illumination.

By contrast, an oriel window projects from a wall at an upper level but doesn’t penetrate the roof plane. A clerestory window sits high on a wall to let light in without altering the roof, and a bay window projects outward from a wall at or near eye level, not through the roof. So the dormer is the one that introduces a vertical window through the roof.