---
title: "Bay window roof geometry"
url: https://digiconsoo.com/page7
description: "How the hips on a bay window roof should be laid out in plan, and the error that forces two pitches."
---

# Bay window roof geometry

[Main page](https://digiconsoo.com/) › Roof geometry

Rule

**Applies to**: Bay and bow window roofs

**View**: Plan, from directly above

**Correct**: Hips bisect the angle at the front wall

**Common error**: Hips set at 90° to the front wall

**Result of the error**: Two different pitches in one structure

Viewed in plan, that is from directly above, the hips should bisect the angle formed by the front wall and the wall adjacent that dies into the house.

## The common error

**Correct**: Each hip bisects the angle between the front wall and the adjacent wall, so both roof planes carry the same pitch and the intersection with the house is shorter than the front wall.

**Incorrect**: The hips are placed at the corners at 90° to the front wall. That creates an intersection with the house equal in length to the front wall, which forces two different pitches into the structure, and it looks wrong.

More bay window roofs are framed this way every year. The [concave hip and regular hip window roofs](https://digiconsoo.com/products/productcategories/bay-bow-bow-window-roofs/) are prefabricated to the correct geometry, so the pitch is consistent by construction rather than by site layout.

[← Cost comparison worksheet](https://digiconsoo.com/page17.html)

[Window roofs →](https://digiconsoo.com/products/productcategories/bay-bow-bow-window-roofs/)

Categories: [Window roofs](https://digiconsoo.com/products/productcategories/bay-bow-bow-window-roofs/)