How deep does a window need to be for inside mount shutters?

It depends on the louver size. 2½-inch louvers need 2 inches of depth, 3½-inch louvers need 2½ inches, and 4½-inch louvers need 3 inches. A hidden tilt adds about ¼ inch. Locks and crank handles can still get in the way, so check the hardware too, not just the depth.

How deep does a window need to be for an inside mount?

It depends on the louver size. The simple rule: 2½-inch louvers need 2 inches of depth, 3½-inch louvers need 2½ inches, and 4½-inch louvers need 3 inches. That depth keeps the louvers from hitting the glass, the window lips or the locks when they tilt. We measure the clearance at every window during the consultation, not just the width and height.

A hidden rear tilt takes about another ¼ inch of depth, which is why the last column runs a little deeper.

If a window is shallower, the L-frame can be pulled out toward the room, but the shutter then projects out of the opening. A 1-inch Z-frame is usually the better fix.

What if my windows have locks or crank handles?

Check the hardware, not just the depth. Crank-out windows are the common case. Picture a 6-foot window made of two crank-outs that swing out, one to the left and one to the right, meeting in the center. The locks at that center line swing up and down and take up about 4 to 5 inches of width.

The two shutter panels meet right there, and louvers in front of the locks would hit them. The stiles, the vertical sides of each panel, are typically 2 inches in the industry. Because we build custom, we widen the two center stiles, for example 2½ inches each, 5 inches together, so solid wood covers the locks and the louvers clear them. We size stiles from 1¾ inches up to 4 inches on sliding glass doors.

Crank handles at the bottom are the other catch. A window can have 3 inches of depth, plenty for an inside mount, and still have a crank handle where the L-frame needs to go. We cut a scoop, a curved notch, into the frame so the handle turns without hitting it. It is tricky work, and we offer scooped frames so the handles clear.

Three-sided or four-sided frame: which is better?

A four-sided frame gives the best look, with mitered corners on all four sides of the window. A three-sided frame, with no frame across the bottom, works well too, as long as the bottom of the window is square. The eye picks up anything that isn't square, and a gap at the bottom of a three-sided frame can't be caulked. A four-sided frame can be.

What does a sill plate do for shutters?

A sill plate is another tool for tight windows. On a typical L-frame or Z-frame, the bottom jamb is 1¼ inches tall. Using a sill plate there instead gains about ¾ inch of height, which can be enough to add another louver. It also helps when a lock sits low on the window where a scoop won't work.

This is part of our inside vs. outside mount guide. To see the options in person, visit our factory and showroom in Lake Forest, or call 949-951-0600 for a free in-home consultation.