Install Ledger and Cross Pieces
This project takes advantage of three windows in perfect position to receive a window seat. The window sills in this home were damaged by animals. Replacing the sills gave rise to the decision to build in a window seat. The sills were replaced but the finish trim was left off -- the window seat will cover the area where the trim would go.
To begin, measure and cut 2" x 4" boards that will serve as ledger boards just below the window sills at the height of the window seat. Note that a 3/4" piece of melamine and a 3/4" trim piece will be installed on top of these ledger boards, so make sure to leave room.
Make sure the outside corners of the ledger boards are cut at the right angle to receive cross pieces running from corner to corner. The ledger boards should also be held back approximately 2 1/4 inches from the edge of the wall so that there's enough space to receive the cross pieces and the melamine from panel.
Using 16p nails, nail the ledger boards with the wider side of the 2" x 4" flat to the wall.
When the ledger boards are in, measure and cut 2" x 4s" to serve as the front cross pieces at the top and the bottom of the window seat. Make sure the top and bottom pieces are flush and plumb with each other.
Nail the top cross piece into the angled ends of the ledger boards, making sure there's enough room for the melamine panel.
Nail the bottom cross piece to the bottom boards.