For most people/windows, the question of “should Roman blinds be inside or outside recesses” comes down to nothing more than personal choice. This is largely based on the look you want to achieve, but potentially by how serious you are about reducing light leakage around the sides of the blind too.
Roman Shades may be mounted inside or outside the window frame. When ordering your window blind of choice, make sure you specific the correct option that best fits your application. You will need at least 1 inch of window frame depth to mount roman shades although at least 3 inches will be needed for a flush mount.
Outside Mounted Blinds & Shades Block Out More Light and Provide Full Coverage. Since outside mounted blinds and shades cover more of the window and frame than inside mount blinds, they provide more light coverage.
Outside mount (sometimes referred to as outside brackets) means that a blind or shade is installed outside of the window frame while an inside mount is installed inside the window opening. Inside mount blinds are often flush with the window's opening and do not cover up the trim.
Inside mount blinds and shades are installed with the brackets attached to the inside of the window frame, and depending on the bracket, they can be placed almost anywhere on the top, or the corner of the inside window frame.
In summary, for Venetian, roller and vertical blinds, we would recommend they be hung from within the recess. However, Roman blinds would be better suited outside the recess, as they are able to let more light enter into the room.
As opposed to inside mount when the coverings are mounted inside the window frame, outside mount is mounted on the wall above the window and directly on the trim. Because of this the blinds or shades will need to be wider than your window opening.
Outside mounting can be used on all window types, regardless of how deep or shallow they are. Outside mount blinds result in less light leakage because you can get blinds that are wider than the window glass, providing more coverage, which can affect the impact of window blinds on daylight-linked dimming.
We recommend letting your roman shade extend at least 1”-1.5” on each side of window to avoid light seepage. So whatever is the width of your window from frame to frame, add total of 2”-3” to that.
To minimize light leakage and ensure privacy the blind should overlap the window opening by 4" on each side for a total of 8" on entire width. 2) Measure distance from where the top of the blind will be located to the window sill. The blind should overlap the window opening on the top and the bottom by at least 3".
Hanging a Roman blind inside of the recess may be a little more awkward as you'll have a limited area to work within and angle your tools within, while Roman blinds hung outside of the window recess are best attached to a batten to support their weight, which means one more thing to do but a potentially easier working ...
In addition, Roman shades have a practical appeal. “When you have built-ins and banquettes against the wall, you can't do full-length drapery,” says Rodriguez. “Roman shades can provide windows covering, without having the concerns of wall space or lack thereof.”
Roman shades are always a vertical type of shade, meaning that they always attach from the top of the window (or on the wall above) and hang down over the window.
3⁄4" is the minimum depth required for inside mount blinds.
Inside the recess
This method of hanging blinds positions the blind right next to the window, within the recess. It should be noted that this method isn't always available as, generally, a recess depth of 7.5cm is needed to ensure there is enough room for the blind.
Inside mounting occurs when the blind is installed inside the window frame. Inside mounts are the cleanest look because they fit snugly inside the window frame.
Inside mount refers to blinds and shades that are installed within the confines of a window frame. That means the headrail is attached flush with the top of the window frame and the window treatment is fully contained inside the four corners of the frame itself. Pros: Inside mounts provide a sleek, built-in appearance.
The bottom of your roman Blind should just touch the window sill when fully closed. You should use the shortest drop measurement if they are different at each end of the sill to ensure you don't have one side too long and crumpling on the window sill.
Should blinds rest on the windowsill? Yes, for your blinds to work to greatest effect and to achieve the right visual finish, window blinds should rest on the windowsill.