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How to Design a Dormer Window

Meena Valliappan

The credit for introducing dormer windows into architecture goes to French architect Francois Mansart, as early as the 17th century. By bringing dormer windows into sloped roofs, he was able to bring light and air into attic spaces.

Gabled dormer windows are interesting additions to your roof

This dramatically increased the use of attic spaces as they were no longer mere storage areas. Today, dormer windows are also used to maximize the available floor space. They have evolved over the years into many shapes,sizes and styles. They also add to the aesthetics of a home, breaking up the monotony of large, sloping roofs and adding unique focal points.

  1. Determine the position of your dormer window. If your primary purpose is to maximize your available floor space, then locating your dormer window in the rear of your building is preferable. If bringing in light and adding to aesthetics is your objective, then position your dormer window along your front facade.

  2. Decide on the size of your dormer window. This depends on the proportion of your dormer window to the facade of your home. A general rule of thumb is to ensure that each window does not exceed 8 feet 2 inches in width. If you require more width, consider designing two dormer windows, but allow at least 4 feet of space between them.

  3. Choose the shape of the dormer window you would like to use in your home. There are five different types of dormer windows: eyebrow dormers that are arch-shaped, the traditional gable dormer that has two vertical planes with a gable roof, the hipped dormer that is similar to the gable dormer except that its roof has three sloping planes, the shed dormer that has only one single front sloping plane and the recessed dormer that is set back into the roofline. You can choose one style for all your dormer windows or incorporate a variety of styles.

  4. Place a tracing paper over your home elevation. Using a pencil, trace the building's outline onto your tracing paper.

  5. Draw the front face of your chosen style of dormer window onto your tracing paper, in the location you want it to be built. If you have more than one dormer window, draw all of them.

  6. Observe the finished drawing and consider whether the scale, size and proportion are in relation to the rest of the building. If the windows seem to overpower the roofline, consider reducing their size.

  7. Adding details can create decorative dormer windows.
  8. Consider adding finishing details to your dormer window. You can add grooves along the exterior, casements along the exterior face, or decorative detailing along the face of the dormer roof. Add a turret to the roof of your dormer, or position a flower box in front of your dormer window.

  9. Choose the glazing material and consider whether you want to tint the glazing, have curtains or incorporate shutters. Decide whether you want to continue the same roofing material as the rest of your home on your dormer window or make it stand out by changing the material.

  10. Draw the finalized design with markers onto your tracing paper. Pass your finished design onto your builder, who will be able to carry out your design.

  11. Tip

    Generally it is better to incorporate more than one dormer window into your building elevation because a solitary window looks odd.