Openings

Openings are voids in a wall such as windows, doors, or even niches. The following guidelines apply to such openings.

4a. Openings should be vertical rectangles.

Rectangles with heights between 1.5 to 2 times their width tend to look best. For plain rectangular openings the golden ratio of approximately 1.618 is commonly used. For arched openings (either pointed or round), a height of 2 times the width is commonly used.

This guideline is not applicable for:

• Top story or dormer windows, these may be square (though they may also be vertical).
• Cellar windows, these may be square or even horizontal (though they may also be vertical).
• Specialized openings such as arrow-slits in fortifications.
• Ground floor shop display windows.
• Spaces between columns in a non-arched colonnade. Depending on intercolumniation, these may be narrower.

With construction methods used in the past, the width of spans over openings was limited. The wider a span was, the more effort and expertise was required to ensure it was structurally sound. In order to maximize light without increasing structural complexity, openings were often made taller than they were wide.

Additionally, vertical rectangles relate to the human form. Something we are aesthetically comfortable with.

4b. Entrances should be obvious.

Buildings are built with the purpose of being entered. To effectively serve this purpose, entrances should be obvious. The simplest way to bring attention to an entrance is to place it in the center of a sub-mass, or building, and align it vertically with focal points (see Guideline 3. Focal Points and Framing Mechanisms).

Because there is normally only one door per sub-mass, per façade, this also maintains the symmetry of the sub-mass.

Centered entrances are not applicable for less formal buildings such as row houses or other residences. Entrances can be centered, though they may also be located off to the side. However, in both formal and informal buildings, entrances should be obvious.

4c. Circular (or oculus) and semi-circular windows should be used as accent or feature windows only.

This is not applicable for dormer windows: these may be circular.

There are two primary reasons why circular and semi-circular windows were used sparingly in the past.

1. They required much more effort and skill to construct and install than a regular rectangular window.
2. The surface area is smaller than that of a rectangular window with the same outer dimensions. Thus, they let in less light and have a reduced viewing range.

Because circular and semi-circular windows were both more expensive and less functional they were used sparingly as decorative elements or in locations where their shape was advantageous, such as a the apex of a peak or a tympanum.

Today, the above two reasons still hold true. However, there is also an aesthetic reason to not use circular and semi-circular windows as the primary window shape.

Circles and semi-circles are powerful shapes. Because they become smaller on top, they act as focal points and draw the eye in a way that rectangles simply do not (see Guideline 3. Focal Points and Framing Mechanisms).

If circular and semi-circular windows are used as the primary window shape, they compete for attention and draw the eye all over the building at once. This results in no focus, no ordered visual progression, and no harmony.

4d. A circular window (or oculus) should be roughly 0.8 times the width of the rectangular window below it.

This is also applicable for dormer windows. This is not applicable for windows of differing scales, such as rose windows.

When placing a circular window above a rectangular window it would seem logical that the two should have equal widths. However, because circles are such a strong shape (See 4c. above), they should in fact be smaller. A diameter of 0.8 times the width of the rectangular window seems to work well. If they are the same size, the circular window will draw the eye disproportionally, compared to the rectangular window below, and appear top heavy.

4e. Horizontally, there should be an odd number of openings.

This is applicable for entire buildings and dominant sub-masses, such as center and book-ending sub-masses. This guideline is softer for recessive sub-masses, such as connecting and flanking sub-masses. For recessive sub-masses, Guideline 4f below takes precedence. For more on dominant and recessive sub-masses, see Guideline 1. Subdivide, Subdivide.

An odd number of openings places an opening in the center of a sub-mass or building. The eye is naturally drawn to the center of a building and focal points are often used to enhance this effect (see Guideline 3. Focal Points and Framing Mechanisms). Placing an opening where the eye lingers, as opposed to a wall, connects the viewer to the interior and makes the building feel more inviting.

4f. Neighbouring sub-masses should have a different number of openings horizontally.

A different number of openings between neighbouring sub-masses is important for establishing the rhythm of a building. Neighbouring sub-masses with the same number of openings horizontally, make a building feel static and should be avoided. One exception to this guideline is: if neighbouring sub-masses have significantly different widths, they may have the same number of openings. However, this should be used with caution and only by experienced architects intent on achieving a certain effect.

Ideally all sub-masses will have an odd number of openings. However, sometimes due to size limitations, it is not practical for all sub-masses to have both an odd number of openings and a different number of openings than their neighbour. In these cases it is acceptable for recessive sub-masses, such as connecting or flanking sub-masses, to have an even number of openings.

4g. Horizontal spacing between openings, and between an opening and the corner of the building, should be between 0.5 to 2 times the openings’ width.

However; similar to the principle of Guideline 4f above, spaces between openings should not be the same width as the openings. This leaves the façade looking static and flat. Spaces should always be either narrower or wider than their adjacent openings. This contributes to the rhythm of the façade.

The spaces between openings are important as they ensure the building appears structurally stable. This is especially true on corners. Therefore a façade, or even just a single story, of only windows with no spaces between them should be avoided. Corner windows shall also be avoided as they leave the building looking weak and unstable.

Conversely, large empty spaces should also be avoided. If the floor-plan does not allow for a window or door, a niche or a moulding detail can be used to emulate an opening.

4h. Use a consistent arch shape (all pointed or all round).

Pointed arches belong to the Gothic style. Round arches belong to most other styles. Generally it is advisable not to mix architectural styles. Therefore it is also advisable not to mix pointed arches with round arches.

There are different round arch variants. The most common is the semicircle. However, there are also segmental and three-centered arches. It is acceptable to combine the round arch variants in instances where openings have varying widths but a consistent height is required.

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