Arched windows add architectural value to any home. They add style and detail to the facade and suggest a classic, formal style for the interior. An arched window is typically a rectangular or square window section topped with a half-circle window. It can be either one or two separate units, but is viewed as one window. Constructing roman shades for them requires a high level of design and sewing skill, familiarity with a jig-saw and a working knowledge of roman shades and their components. Knowing that shades cannot draw past the widest horizontal point of the window is key to creating a satisfactory shade.
Measure the area the shade is to cover. Record the width at the bottom of the arch, the length from the center of the arch to the required bottom of the shade and the length from the bottom of the arch to the bottom of the proposed shade.
Make a template of the arch section. Use cardboard or heavy construction paper to create a pattern that is the exact size of the arch where the proposed shade will rest. For example, if the shade is an inside-mount shade, the template must be the exact size of the inside of the window frame arch.
Cut the arch shape from 1/4 inch plywood. Sand the edges down to 1/16 inch less than the actual template pattern on the arched section only. This allows for the thickness of the fabric that will be wrapped around the form.
Cut the fabric for the shade. The length of the fabric required is the measurement from the top of the arch to the bottom of the shade, plus a bottom hem allowance, plus the amount allocated for side hems and any additional design additions, such as front tucks. Cut the width of the fabric equal to the width of the finished shade, plus the side hem allowances. The hem allowances for both the width and length are arbitrary measurements based on the design, and are selected by the sewer or designer.
Lay the fabric flat on the work table, wrong side up. Position the arch template on the fabric, leaving just the amount for the side hems free all around the arch and mark the cutting line to include this hem allowance. Cut the fabric to this line. Cut only the arch section, which is the top of the shade, do not cut across the bottom of the arch.
Cut a 1-by-2 board equal in length to the width of the finished shade less 1/4 inch. This is the headrail for the blind hardware. The eye screws will fasten to the bottom of this board, on one of the 2-inch sides. Fasten this board to the center of the bottom edge of the back side of the plywood template. Position the 2-inch sides at right angles to the arch board. The headrail sits behind the plywood, and the bottom edge of the arch board is even with one wide side of the board. Attach the board to the plywood with angle brackets on the back side of the arch.
Construct the roman shade in your customary manner. The method of construction will not differ because of the arch. Rather than have a top section of shade that wraps around a headrail or is attached with hook-and-loop tape to the front of the headrail, the top of the shade is shaped like an arch and covers the plywood. Attach it to the arch by wrapping the allowed seam allowance on the top curve of the arch from the front to the back and stapling the fabric to the back side.
Insert the eye screws along the bottom of the headrail and thread the lift lines.
Mount the shade to the window in whatever manner you choose. Typically angle brackets are placed equidistant along the headrail position and the headrail rests on top of the brackets and are attached with screws.
Very light-weight quilt batting may be sandwiched between the fabric and the arch for a more upholstered look.
Because these shades cannot be removed for cleaning, spraying them with a fabric static inhibitor to reduce dust collection.