Here is how to overlay your existing wall and create drop panels around windows that encroach the wainscot plane.

First, add back banding material around the window trim to accept the chair rail depth with a slight reveal. In this particular remodeling project, 1/2 inch birch plywood was applied to the wall and shimmed out 1/8 inch, using that space to straighten the wall when needed. A 1/8 birch panel is inserted into each drop area. Then, a Bolection Moulding is applied around the rectangular drop areas.

Notice the rails next to the windows that have been notched around the existing window stool. The previous apron was removed to allow for a drop panel below. Then a small cove moulding is applied under the existing stool on top of the new style under the stool.

There are a lot of techniques I use to install and layout wainscoting that are not well understood. Several unique tools and a solid understanding of plane geometry is vital.

An excellent tool that you'll need at least one of, [I have two minimum, one for each cut on each end], is something called a T-Bevel. Below is an excellent T-Bevel to buy from Rockler. Once an angle has been determined, you simple divide this angle with a compass trick, reset your bevel, and mark the back side of your bolection moulding to cut sharp angles inside 45 degrees.

The increased angle cuts are difficult to make, but there are a couple of tricks I have learned to cut them with an electric miter saw without worry about losing your fingers. Be sure and drop back by to read and download more information.

T-Bevel Sliding Square