Roman Shades for Inside or Outside Your Window Frames?
Shades are attached to mounting boards (known as headrails) that anchor the fabric and support the operating hardware. These headrails screw to the window casing or the wall. The design and structure of your windows may determine if your shades can mount inside or outside the window frames.
Mounting inside the window frames requires at least a 1" depth inside the frame. For certain types of operating hardware, the minimum is 1 3/4" depth for a flush fit. Inside mounted shades stack to the top of the window, reducing the amount of clear window even when fully raised. Plastic or soft foam casings may not hold the anchor screws securely. Protruding window hardware can interfere with an inside mounted shade.
Certain soft shades are only outside mounted - unless the windows have a very deep inset from the wall. These are the billowy types like the Austrian, Balloon and Venice. They need depth.
Outside mounts can hide shallow molding and make the window appear larger by extending above and beyond the casings. They can also span a group of narrow windows (such as kitchen casement windows) giving a unified look that could appear choppy otherwise.
Inside mounted shades enhance the trimwork which creates a border around the shade fabric. They have a crisp, tailored look. Layering drapes or valances over Roman shades calls for an inside mount where possible. This minimizes the projection of the combined window treatments into the room. In busy areas, inside mounted shades are less vulnerable to brushing and snagging as people bustle by.
Mounting a Roman shade outside the window frame requires 2" to 3" of wall above the top window trim. Deep window trim with projecting lips or blocks will require a deeper headrail to project the shade off the wall and clear the molding. Flaps or caplets are usually required on the ends of the headrail to conceal the mounting and operating hardware.
Skewed Windows? Almost always mount outside
Where the windows are skewed or out-of-square (i.e. the sides are not at right angles to the top and bottom) inside mounted shades will show angled gaps down the sides. Or they will drag on the side casings when lowered. Minor skewing can be overcome by using a more narrow shade where possible.
If the head casing is skewed, the shade can be leveled by using shims behind the headrail. That will leave a gap between the headrail and the casing.