Side shapes and arch shapes

Side shapes and arch shapes (Chris Ecker)

Exterior Window Treatments: A Primer

Thinking and planning

When designing your dome for residential or commercial use, it’s worth thinking through multiple construction possibilities early in your planning. Floor plans and fixtures might take up the bulk of your time, but an often overlooked issue is the dressing out of your exterior windows.

This article pertains to both inset and augmented windows and has some practical carry over for larger openings, such as entry ways. For this article, the chosen window treatment options are placed into a few broad categories that include arches, dormers, awnings, arbors and fabric. Arguably there are many ways to catalogue such a potentially vast subject, and so this article is not meant to be all inclusive.

Some all-important questions

When initiating your planning, consider asking yourself a few questions. If there are some unknowns in any given evolution, sometimes it’s helpful to ask: who, what, where, when, why and sometimes how. Examples might include:

WHO will do most of the construction? WHAT are my materials? WHERE am I purchasing my materials? WHEN do I need materials on site? WHY do the choices I’ve made appeal to me? HOW will Building Codes affect my final appearance?

Other questions might include: Is there a definite and singular style that I have in mind, or am I flexible and willing to incorporate different but similar styles?
Do exterior window treatments need to be altered near cardinal points around the dome perimeter to best capture the sun or a picturesque view? Has the exterior color palette been selected? Will the finished style blend in with landscaping choices? Does this style compliment the neighborhood? Are there any special transportation, unloading or staging issues?

If you can answer these questions:

Then you probably have a solid handle on how to tackle this phase of your dome planning and construction. MDI can certainly shed expertise on your project. And your spouse, general contractor and tradesmen are good sounding boards too. Each of these resources will undoubtedly bring up additional items to ponder.

And if you are involved with a large commercial dome, you probably already have at least one committee to satisfy. When planning, sketching out several options can be helpful to include or eliminate options. Photos of your construction site and your construction progress, especially after your Airform has been inflated, can be helpful for determining scale of window treatments.

It sounds odd to start with the side walls of your exterior window treatment, but planning any foundation can quickly alter your entire design. Certain construction materials and finishes will look better on a dome with a smaller radius. The inverse is also true. Dome height will also weigh significantly into your finished appearance.

A beginning

One way to begin is by picturing the window treatment side profile. Generically speaking, most shapes are divided into organic (soft, round) and geometric (straight lines with angles). With that in mind, three basic side wall profiles would include flush (geometric; perpendicular to the ground), convex (organic; bulging outward from the dome) and concave (organic; swinging inward toward the dome).

Combining these profiles will allow for more complex shapes. Besides profile shape, you need to define the structure or mass of the sides. Start with easy questions: Is the side going to be simple or complex?

Then try to visualize or sketch one or more of these options: the length of the treatment (does it touch the ground or terminate beside the upper, mid or lower window frame?), solid side walls, no side walls, columns, solid material, veneer, brick, block, open block, stone or specialty materials such as wine bottles laid in mortar.

How about inlaid designs, patterns, vaults or cubbies? Will there be any difference between the exterior and interior faces of each side wall? With a few choices made you will see that the sides of your treatment can easily make or break the final appearance. These options will provide two dimensions: height and breadth (away from the Airform).

A head-on view

Now consider a head-on view of your window treatment. Arches sound simple enough, but a quick scan of an architectural reference will quickly debunk simplicity. These shapes combined with your selection of sides will illustrate two dimensions from the front or head-on view: height and width. Here are some basic arches in non-technical terms:

  • Jack or flat – really not an arch at all, but used for complex arches.
  • Semi-circular – a half circle.
  • Segmental – as it sounds, a segment of a semi-circular arch, or bowed arc.
  • Pointed semi-circular – a semi-circular arch with a distinct but typically small inverted V at the apex.
  • Bulls-eye – a full circle.
  • Horseshoe – the majority of a bulls-eye arch, set on sides and open below.
  • Onion, turnip or pointed horseshoe – a horseshoe arch with a concave upper segment and an inverted V at the apex.
  • Multi-centered or elliptical – a flattened semi-circular arch.
  • Triangular – an inverted V without rounded sides.
  • Gothic – a pointed, rounded, inverted V; can be upright, or squat in appearance.
  • Trefoil – typically a more complex gothic arch that contains three joined segmental arches, laid in a triangular pattern with the middle segmented arch making the trefoil’s apex.
  • Tudor – a flattened inverted V with a distinct apex angle and rounded corners.
  • Venetian – a semi-circular arch, centered and suspended over an open jack arch that is all open below.
  • Nestled – any type arch within itself, multiplied any number of times.
  • Bell or flared – more of a side design, where the lower side portions swing out from the vertical center line of the arch.
  • Vaulted or complex – usually comprised of multiple convex or convoluted indentations, equally or mathematically spaced across the interior span.

Moving on

With the arches in mind, the next option is to combine the shape with your previously chosen sides. Then decide whether to leave the void of the arch open, or to wrap the upper arch’s profile on its vertical axis to enclose a portion of the arch. For instance, a semi-circular arch wrapped like this would create what is commonly referred to in the awning business as a dome. It would be better called a half-dome. (See Figure 1 for side and arch examples.)

If arches are too permanent or costly, awnings may be a better fit for your dome. They will appear lighter and will likely weigh much less. Several awning shapes are available from many manufacturers in the US. Most can have a valance or flat skirting added to make the form appear taller. If a valance is chosen, there are often border trims to select from also. Common choices of these three dimensional forms include:

  • Shed or Patio – a simple triangle or a slanted low box with the side attached to the structure taller than the terminal side.
  • Dome – one quarter of a sphere.
  • Long or Broad Dome – a dome, halved vertically and stretched apart with the same material spanning the tunneled area created by the stretch.
  • Convex or Waterfall – one quarter of a cylinder.
  • Concave – basically a shed form with a taller structure side and downward sloped profile ending on the terminal side.
  • Canopy – one half of a cylinder formed as a tunnel often over a walkway.
  • Marquee – the flat end cap attached to the terminal end of a canopy form.
  • Domed Canopy – a tunnel canopy with a dome awning attached to the terminal end.
  • Gable – a series of squat equilateral triangles that form a typical roof line, jutting off of a structure, also often used as a walkway.

Complex forms such as a long dome with marquee can be manufactured also. Some of these forms would be very difficult to form against the radius of your dome – but there’s probably someone who would gladly relieve you of your money to construct anything you’d like. It often pays to be a little handy! (Figure 2 has several of these awning examples.)

Another consideration

Maybe arches and awnings are out of your budget or just too chunky for your taste. Have you considered fabric? Briefly, there are two commercial options widely available. Tensioned fabric, sometimes called shade sails or sun shades, and non-tensioned fabric such as shade cloth. Tensioned fabric can be made into just about any shape and can accomplish what few other building materials can: blending geometric and organic shapes.

The finished form is defined by stakes or fastening points and the amount of fabric tensioned between these points. Shapes can be made simple, flat and multi-sided, or into complex forms like a circus big-top or twisted saddle-like shapes. This tensioned choice will afford you many versatile and visually appealing structural options.

Non-tensioned materials are often flat panels cut to fit a roof line or rolled onto a cylinder, supported by structure brackets and cantilevered poles. Some non-tensioned fabrics are rolled up on spring loaded awning cylinders. Either fabric could be ordered translucent to let sunshine partially through or be made from impermeable material, such as MDI’s Airform material. Air flow, variable shading, colors and patterns are some distinct areas of fabric versatility. (Because of so many fabric possibilities no illustrations are provided with this writing.)

Traditional dormers

If you’re into more conventional construction and are looking for a traditional feel, dormers provide all this with many options. Here are a few:

  • Arched – an elliptical, arched roof set on side wings.
  • Eyebrow – similar to arched dormer but with side overhangs and less rise in the arch.
  • Shed – a flat roofed dormer.
  • Steep Roof Shed – a shed dormer located on a roof with a sharp up-angle.
  • Gabled – an inverted V on side wings.
  • Pedimented – a closed triangle atop side wings, often incorporating classic Greek or Roman styles.
  • Hipped – a gabled shed having a flat roof face.
  • Flared – gabled dormer with a second, flatter angle near the terminal edges of the dormer.
  • Pyramidal – two faces for window placement create a V that juts out from the roof.
  • Recessed – typically a pedimental dormer that juts out further than flush from the window to create an overhang.
  • Wall – lower half of window is flush to the wall, the window frame interrupts the wall/roof junction, and the covered, upper half of the window rises above the roof line.
  • Polygonal or bay window style – a dormer style that has several facets and angles for walls. Cover will vary with the different designs. (Figure 3 illustrates most of these dormer styles.)

More options

The last treatment types discussed in this article offer whimsical-to-formal, airy, less permanent and less expensive options. Three very similar construction types include an open arbor, roofed pergola or vine or flower laden trellis to surround your window. (Since there are so many options available from libraries and websites, no illustrated examples are provided here.)

Wood and plastic framing are common material options, and the final product(s) can often be built on-site by the dome owners, congregants or employees. Two other often overlooked material choices are organic and recycled materials from your surroundings. The final shape or form can be just about anything you can imagine from basic, boxlike structures to elaborate, multi-voids that incorporate fencing, walls, seating and planters. Colors, textures and weight of the final product are just as elaborate as the previous options discussed above.

It’s worth mentioning that time at the library, reviewing MDI’s website and searching the world wide web should be considered time invested in your construction. With so many choices, you’re bound to find your perfect exterior window treatment solution. Just be sure to start your planning early to avoid last-minute, pinch decisions and budget-busting commitments.

Awning examples

Awning examples (Chris Ecker)


Dormers (Chris Ecker)