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DIY: Cabin Window Boxes

An easy weekend project to add charm & beauty to your place

By Raj Chaudhry
Published: February 15, 2013
Photo by Raj Chaudhry
For adding color and charm to your place in the woods, few weekend projects can boast the impact of window boxes. Here’s a clean, classic design that can be adapted to suit almost any style of home, from log cabin to lake cottage. The boxes shown here are crafted from western red cedar, a lightweight, beautiful and naturally rot-resistant lumber. Other good options include redwood, cypress and pressure-treated lumber.

Making the boxes

1. Determine the box size. The most common rule of thumb calls for matching the length of the box to the width of the window it will accompany, measured from the outside edges of the window frame.

Illustration 1
Photo by Raj Chaudhry
2. Cut the end pieces. Each box has two ends, which are cut from a length of 1x6. (A cedar 1x6, after surfacing at a mill, is actually 1 1/16-inch thick and 5 1/2-inches wide.) The back edge of each end piece is cut square. The front edge, however, is cut at a 10-percent angle and tapers from a point 5 7/8-inches long at the top to 4 7/8 inches at the bottom (Illustration 1). Make this cut on a table saw by setting your miter gauge to 10 degrees. Cut both ends identically. Keep your cutoffs for later use.

PHOTO A: Use your end piece to set the angle of the table saw blade.
Photo by Raj Chaudhry
PHOTO B: Using the table saw, rip the bevel on the front board.
Photo by Raj Chaudhry
3. Rip the front piece. Begin with a 1x8 board that is longer than the finished length of the box. Bevel the top and bottom edges (Illustration 1). To find the proper angle, simply tilt your table saw blade to match your end piece (Photo A). After setting the saw’s blade and fence, rip one edge of the front board. Then place the board on a flat surface, beveled edge down, and use an end piece to mark the line for the second cut (resulting in a width of about 5 9/16 inches). This ensures that when the box is assembled, the tops of the front and ends will be flush. Use the reference mark on the front board to position your rip fence (prior to making a final cut, you may want to make a test cut on scrap) and cut (Photo B).

4. Crosscut the front, back and bottom boards to length. If working with a rip blade, change to a crosscut or combination blade. Reset your saw blade square to the table. Then make your cuts. The front, back and bottom boards should all be the same length – matching the width of your window. The design calls for the back to be cut from 1x6 (5 1/2 inches) stock and the bottom to be cut from 1x8
(7 1/4 inches) stock. If you use the suggested dimension lumber, no additional rip cuts are required.

5. Attach bottom to back. Assemble the box with 2-inch long, stainless steel, No. 8 square-drive wood screws. Each screw will require two pre-drilled holes: a 3/8-inch bore to countersink the head, and a 7/64-inch pilot hole for the threaded shank. (Combination bits are also available that will drill both at the same time.) Bore the large hole first. In fastening the bottom to the back, locate one screw an inch or so from each end, with an additional screw about every 6 inches in between. These holes should be centered just under 3/8 of an inch from the back edge of the bottom board (half the thickness of the lumber). Drive the screws through the bottom into the lower edge of the back board, checking for square. The box will need to be disassembled in subsequent steps, so don’t over-tighten the screws.

6. Attach sides to back & bottom. The side pieces are inset about 1/2-inch, meaning that each is centered about 7/8 of an inch from the end of the box. With the sides in position, drill pilot holes for a pair of screws up through the bottom. Screw into place. Pre-drill for a second pair of screws through the back and attach.

7. Attach front to ends & bottom.  Drill countersink and pilot holes for screws to attach the front to the ends – a pair through the front into each end – then from the bottom board to the front board, every 6 inches or so. When drilling from the front into the ends, make your counter-bores about 3/16 of an inch deep. These holes will later be covered with wooden plugs. To attach the front board to the bottom, draw a line about 1 1/4 inches from the front edge of the bottom board. This represents the center line of the front board. These holes will have to be angled slightly. Use a hand drill, employing the scrap of wood saved in step 2 as a visual guide. You can also use a sliding bevel, set to the same angle as the sides.

Disassemble the box

1. Drill drain holes. Drill a series of 3/8-inch diameter holes in the bottom to allow water to drain. Stagger these along a line about 4 inches from the back edge, with about 6 inches between them. By locating the holes toward the front of the box, you can prevent water from trickling down the side of the house.

2. Re-assemble with glue and screws. Assemble the box in the same order as before, this time adding waterproof yellow woodworkers’ glue to each joint and fully tightening all screws. Wipe off any excess glue that squeezes out with a damp rag.

PHOTO C: Trim the plugs with a thin, flexible kerf saw or chisel.
Photo by Raj Chaudhry
3. Plug screw holes. For a nicely finished window box, use a 3/8-inch-diameter plug cutting bit and cut screw-hole plugs from scrap cedar. Cut the plugs free of their board on a bandsaw or simply pop them from their holes with a screwdriver. It never hurts to make a few extras. Apply a dab of glue and tap each plug into place, taking care to keep the grain of the plug oriented with the grain of the box. This will make the plug less noticeable. Wipe away any excess glue with a damp rag. After the glue has dried, trim the plugs close to the surface with a flexible, thin kerf saw or a chisel (Photo C).

PHOTO D: Rip the bracket mounting boards to 2-inches wide.
Photo by Raj Chaudhry
PHOTO E: Crosscut the bracket mounting boards to 151/4 inches.
Photo by Raj Chaudhry
4. Finish sand. Sand all the parts, working up through progressively finer grains to 150 grit paper. Once finished, clean the boards of sand and dust.

5. Coat. For western red cedar, applying a finish is not strictly necessary. But a penetrating exterior sealer will improve the box’s longevity. Cedar finished with a clear sealer will generally weather naturally to its characteristic silver. For more color, a translucent exterior stain can be applied.

Building brackets
Flower box brackets are available from home centers and hardware stores. But for the best match with your boxes, you can also make your own.
A pair of brackets is required for each window box. For window boxes over 36 inches long, you might want additional brackets for support.
Here’s how to make brackets to complement your boxes:

1. Cut bracket-mounting boards. On the table saw, rip 1x6 cedar stock to 2-inch-wide strips (Photo D). Then trim the pieces to their finished length, 15 1/4 inches (Photo E).

Illustration 2
Photo by Raj Chaudhry
PHOTO F: Bandsaw the profile on the front of the bracket. Note that the wood grain is oriented for maximum strength.
Photo by Raj Chaudhry
2. Cut  stock for the bracket supports. The bracket supports should have their grain running diagonally. This helps to prevent the bracket from splitting. Work with stock that is at least 4 3/4 inches wide and 18 inches long – the extra length ensures that the piece will reach the table saw blade while resting securely against the angled miter gauge. Set your miter gauge at 45 degrees and trim off one corner of the board. Flip the board over and make a second cut as shown in Illustration 2. This will leave you with a right triangle with the grain oriented properly (Photo F). Check it for square if necessary.
Illustration 3
Photo by Raj Chaudhry
3. Cut the curved profile. Make a template by tracing your bracket support pattern onto a piece of 1/4-inch plywood, thick cardboard or the like (Illustration 3). Cut it out. Use this template to transfer the outline of the bracket onto each cedar triangle you produced in the previous step. Using a bandsaw, jigsaw or coping saw, cut the profile (see photo F above).

PHOTO G: Route 1/2-inch roundovers on the ends of the brackets standards. A sacrificial backing board keeps the large bit from tearing out grain along the trailing edge.
Photo by Raj Chaudhry
4. Route roundovers on bracket standards. If you have a router and a roundover bit, you can polish your brackets with a 1/2-inch roundovers for a beautifully finished look. To get a clean, square cut on the narrow stock, use the router table’s miter gauge. Rest the piece against a sacrificial backer board to prevent grain tear-out (Photo G). If you lack the equipment for this operation, there are several alternatives: You can use a compass to mark a roundover on the edge of the board and then create the profile on a stationary sander. Or you can just leave the ends square.

An assembled bracket.
Photo by Raj Chaudhry
The completed box.
Photo by Raj Chaudhry
5. Mark and pre-drill for screws. Center the bracket supports on the bracket-mounting boards, so that the top of the window box will be flush with the top of the bracket mounting board (about 6 3/16 inches). Drill and countersink for 2 1/2 inch screws, bored through the back of the bracket mounting boards and into the bracket support. Locate the first of these screws about 3/4 of an inch from the top edge of the bracket support and the second screw about 2 1/2 inches from the top edge. For large boxes, you can add a third screw, 4 inches from the top edge of the bracket support. This screw will have to be shorter: 1 5/8 inches is a commonly available length that will do the job.

6. Sand all parts. Work up through 150 grit, easing all exposed edges. For a slightly more finished look, you can route a 1/16-inch roundover on the front edges of the mounting boards and support bracket.

7. Assemble. Glue and screw. Use the same waterproof glue employed in the assembly of the box and wipe off any excess with a damp rag.

8. Finish sand. Do a final sanding, again with 150 grit sandpaper, and then remove the dust.

9. Add finish coat. Seal or stain if desired, to match the flower box.

Mounting notes
Attach the window box to the house using the following steps:

1. Mark the position of the first bracket. Brackets are often arranged so that their outside edges align with the inside edges of the window casing. For sliding windows, locate the tops of the brackets about an inch beneath the sill. For windows that open outward, make sure the planted box won’t interfere with the windows’ operation.

2. Mount the first bracket. Each bracket requires a pair of 3-inch-long No. 10 stainless steel screws, driven through the top of the bracket mounting boards, where they will be covered by the flower box. No. 10 screws require a 1/2-inch countersink and a 1/8-inch pilot hole. Drill the top hole first and drive in the first screw loosely. Use a level held against the bracket’s side to make sure that it’s plumb. Tighten the first screw to hold the bracket in position. Then drill for the second screw and attach.

3. Locate and install the second bracket. Use a level spanning the two brackets to position the second bracket at the proper height. Drill, plumb and attach as in Step 2.

4. Add the box. Center the box on the brackets and drive a pair of 3-inch screws through the inside back of the box – at least an inch from the top edge – one screw through each bracket mounting board.

5. Protect the drain holes. Before planting the box, add a scrap of fiberglass window screen or a thin layer of pebbles to keep soil from clogging the drain holes.

And – you’re ready to plant!

On weekends, you’ll find Raj Chaudhry working on DIY projects dockside – at least, that is, until he finds a way to put a table saw on a pontoon boat.

•  Measuring tape
•  Adjustable square
•  Table saw
•  Bandsaw or jigsaw
•  Drill
•  Driver bits for drill
•  Screwdriver
•  Assorted brad-point drill bits (1/2-, 3/8-, 1/8- and 7/64-inch)
•  3/8-inch plug-cutting bit
•  Table-mounted router with 1/2- and 1/16-inch roundover bits (optional)
•  Sliding bevel (optional)
•  Flush-cut saw

Materials for Window Boxes
•  Western red cedar. Quantity will vary depending on the width of your window. One 6-foot 1x6 and one 8-foot 1x8 should provide more than enough lumber for a 36-inch box (plus the mounting boards for brackets.) The bottom and front pieces of the box are cut from 1x8 lumber. The back and sides are 1x6 lumber.
•  No. 8, 2-inch long square-drive stainless steel wood screws (about 24 per window box, depending on length)
•  Waterproof yellow wood glue (e.g., Titebond III)
•  Assorted grades of sandpaper (100, 120, 150 grit)
•  Sealer or exterior stain of choice

Materials for Brackets, Per Pair
•  Western red cedar for mounting boards: Enough 3/4-inch thick (approx) stock for two 2-inch wide by 15 1/4-inch long boards
•  Western red cedar for bracket supports: One 2x6 (1 1/2-inch thick by 5 1/2-inch wide), 18-inch long board is sufficient for two supports. Alternately, you can glue two pieces of 1x6 stock together to achieve this width.
•  No. 8, 2 1/2-inch stainless steel wood screws, four per pair of brackets

Additional Tools and Materials for Mounting
•  No. 10, 3-inch stainless steel wood screws, 6 per window box
•  Beam level
•  Pebbles, landscape fabric or fiberglass window screen – enough to cover the inside bottom of your boxes
•  Container soil
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