In our project, the homeowners have decided to turn a narrow window ledge in their dining room into a window seat. They will make the ledge wider so that is makes a comfortable seat and add a hinged lid to allow the area beneath the seat to serve as storage. Dressing the lid with decorative molding to form the lip of the box will also cover the edges of the birch veneer plywood they plan to use for construction.

Step
1

Decide on Project Design and Dimensions
Decide on the project design and basic dimensions and then assemble your tools and materials. We unroll a length of Kraft paper (heavy/coarse construction paper) to protect the wooden floor in the dining room while we work. In the garage, we set up a work surface with plywood and saw horses.

Step
2

Insert a Wide Putty Knife Behind Shoe Molding
Insert a wide putty knife behind the shoe molding beneath the window ledge, tapping gently with a hammer to make a slight gap and avoid damaging the wooden trim.

Step
3

Tap a Pry Bar Between Putty Knife and Shoe Molding
Tap a small pry bar between the putty knife and the shoe molding, again using the hammer. The putty knife will protect the trim as you pry. Use this trick anywhere you remove trim to protect the wood, wall, wallboard, or any underlying material from damage.

Step
4

Remove the Shoe Molding
Remove the shoe molding by prying against the putty knife at several locations along the molding. We will reuse the undamaged wooden trim at the end of the project.

Step
5

Cut Through Caulking
Cut through the caulking at the top of the baseboard with a utility knife to prevent tear damage to the wallboard as you work.

Step
6

Pry off Baseboards
Pry off the baseboards.

Step
7

Detach Trim on Window Ledge
Detach the trim on the edge of the existing window ledge.

Step
8

Remove Nails from Edge
Use a claw hammer to remove the nails from the edge.

Step
9

Remove Wooden Corner Molding
Remove the wooden corner molding around the perimeter of the window alcove.

Step
10

Remove Two Layers of Plywood
Use a larger pry bar to remove two layers of plywood that formed the original window ledge.

Step
11

Remove Protruding Nails
Remove any nails protruding from the exposed surface where your removed the plywood. These will interfere with the new birch window ledge that you will install later.

Step
12

Take Measurements
Measure the horizontal depth of the current ledge, the length of the window opening, and its height from the floor. These are basic measurements for cutting the component panels for the new window seat.

Step
13

Mesure and Mark Cutting Lines on Plywood
Measure and mark the required cutting lines on the plywood. Ultimately, you will need dimensions marked for a new window ledge and a top, front, two sides, two long braces across the back, and a short brace for the center of the window seat. When you cut the new window ledge, allow an additional 1 1/2-inch overhang on the interior edge to cover the area where the base of the new window seat will meet the wall.

Step
14

Secure an 8-foot Aluminum Straightedge to the Plywood
Use an 8-foot aluminum straightedge to assist you in making long straight cuts with the accuracy of a table saw. Secure it to the plywood with its built-in clamp and ensure that it is parallel to the edge of the plywood and your intended cutting line. Note that you will brace the foot of your circular saw against the straightedge, but the saw blade will rest on the cutting line.

Step
15

Support the Birch Veneer Plywood
Support the birch veneer plywood on parallel strips of scrap lumber that serve as spacers. These will lift the plywood off your work surface and stabilize the plywood while you cut. That, in turn, prevents binding on the saw blade. The spacers must run parallel and avoid your cut lines.

Step
16

Ajust Circular Saw Blade
Adjust the blade on the circular saw to that it cuts through the plywood but not into the work surface below.

Step
17

Cut the Panel
Cut the panel with the circular saw. Repeat steps 13 through 17 for each required panel of the window seat.

Step
18

Apply Wood Glue
Apply a bead of wood glue to the edge of one side panel and butt it against the back edge of the front panel.

Step
19

Clamp Panels
Clamp the two panels together.

Step
20

Secure Panel Joint with Nails
Secure the glued panel joint with nails every two or three inches using a pneumatic nail gun. Be sure to hold the nail gun perpendicular to the surface of the wooden panel. Repeat these steps to attach the other side panel to the front panel.

Step
21

Construct the Back
Construct the back using two pieces of cut plywood that are about 6-inches wide and the length of the new seat. These will reinforce the back of the seat at its top and bottom edges. The back will be open between the braces that will give the seat some rigidity.

Step
22

Add a Center Brace
Add a center brace between the front panel and the upper brace on the back to provide additional strength and rigidity and support the top of the seat. Secure it with glue and then drive nails into it with the pneumatic nail gun.

Step
23

Apply Polyester Resin
Mix a small batch of polyester resin (car body filler) and apply it to the exposed plywood edges. We will be able to start painting almost immediately, because this material dries very quickly.

Step
24

Cut the Top
Cut the top from a single piece of plywood. Allow extra dimension/clearance on the top so that its edges will overhang the base seat slightly.

Step
25

Cut Decorative Casing
Cut one long strip and two short strips of decorative casing to make a shallow lip along the front and sides of the top panel, which is also a lid. That lid must fit over the edge of the base seat without binding when the top opens and closes. Use a power miter saw to make 45-degree cuts on the ends of the casing.

Step
26

Apply Glue
Apply glue to the edge of the plywood on the top panel.

Step
27

Slide Casing into Position
Put the long piece of casing on top, sliding it into position so that the inside of the mitered cut is just at the edge of the wood on each edge of the panel.

Step
28

Secure Casing with a Pin Nailer
Use a pin nailer, a smaller pneumatic nail gun that drives brads, to secure the casing. The finer nails will stop the molding from splitting.

Step
29

Apply Glue
Apply glue to a short piece of the casing cut for the end of the top panel.

Step
30

Slip Top Panel into Position
Slip it into position and ensure that the mitered corners of the side trim fit flush with the front trim.

Step
31

Secure Top Panel
Secure it to the top panel with the pin nailer. Repeat steps 29 through 31 for the other casing at the other end of the top panel.

Step
32

Paint Window Seat
Paint the window seat, after filling any nail holes.

Step
33

Install New Plywood Window Ledge
Install the new plywood window ledge. Earlier, when you cut the ledge, you allowed a 1 1/2-inch overhang on the inside edge to cover the seam where the window seat will join the wall.

Step
34

Set Window Seat in Place
Set the new window seat in place, lifting the plywood window ledge and sliding the back/brace of the seat underneath. Secure the window ledge.

Step
35

Pre-drill Clearance holes
Pre-drill clearance holes to attach the window seat base to the wall, after locating and marking studs with an electronic stud finders.

Step
36

Drive Screws Through Back Braces
Drive screws through the back braces into the wall studs.

Step
37

Slide in Shims
Slide shims into the gap between the base of the window seat and the floor along both the front and sides. Score them along the edge with a utility knife and break off the excess.

Step
38

Attach Piano Hinge
Attach one side (wing) of a piano hinge to the rear edge of the seat/lid. Orient it so that the hinge knuckles will be visible above the lid when it is closed and the two "wings" of the hinge are downward. The hinge runs the full length of lid and typically attaches with countersunk screws.

Step
39

Set Lid in Place
Set the lid in place and secure the other side of the hinge to the front edge of the new plywood window ledge.

Step
40

Test the Top
Test the top to ensure that the hinge moves freely and the lip does not bind against the base.

Step
41

Reinstall Trim
Reinstall the trim around the window opening and on the joint where the window seat meets the vertical wall.

Step
42

Reattach Baseboard and Shoe Molding
Reattach the baseboard and shoe molding along the base of the seat where it meets the floor. Fill all the nails holes. Touch up the filled holes and scuff marks with paint.