Back To The Family Handyman
Del.icio.us
Digg
Reddit
Facebook
StumbleUpon
TwitThis
Framing a New Rough Opening
Use a sledgehammer to knock the king studs and trimmers away from the ends of the existing header. If sheathing and siding nails are attached, cut through them with a reciprocating saw or yank them out with a “cat’s paw” nail puller. Remove the sill, too.
Determine the window rough opening width. Manufacturers list the rough opening height and width with each window. Ours was 100-3/8 in., so we cut our headers 106-3/8 in. long—6 in. longer to accommodate the two pairs of 2x4 trimmers. Toenail the new king studs and one trimmer to the top and bottom nailing plates using 16d nails and install the two header members. Toenail the top of the header into the top nailing plates, then add the second trimmers.
Determine the rough opening height, then “sister” new cripples alongside the existing ones to raise the sill height or cut them shorter with a reciprocating saw to lower it. Nail the sill to each cripple and to the trimmers on each side. We installed two sills to solidify the large opening and support the window.
Rally Your Neighbors to Hoist In the New Window
Rustle up your neighbors again and lift the new window into the rough opening. Temporarily support the window, then on the inside, use a flat bar to center the window in the opening from side to side. Shim and level the footboard. Next, use the level and shims to plumb and straighten the side jambs. Shim the top straight and level too. When all four sides are level, plumb, square and straight, drive 10d finish nails through the extension jambs and shims into the framing. Take your time.
Since bow windows extend beyond the exterior wall, they need added support. Our Pella window came with two preinstalled cables running from the bottom of the footboard up through the headboard.
If space is limited above the window, secure the cables to the rafter tails or to blocking that’s securely nailed between the rafter tails.
Trim the Exterior Carefully—So the Window Doesn’t Look "Stuck On"
The closer you match the exterior details to those of the existing house, the more natural the window will look. Since every house is a little different, your exterior trim details will almost certainly vary from ours, especially if you have brick, stucco or vinyl siding. But the same general steps still apply.
Begin by insulating and enclosing the bottom. Hold your 3/8-in. plywood soffit material to the underside of the window, trace the profile onto it, then use a circular saw to cut it to shape. Use this as a pattern to cut the 2-in. rigid insulation and the 3/4-in. plywood nailer. Make sure the edges of all three layers are even with the edges of the bow window as you install them. After enclosing the top (Photos 12 and 13), install the side and bottom flashings.
If the top of your window is within 6 in. of the soffit, you can insulate it, then enclose it using a flashing material and technique. Larger spaces require you to install sheathing, then siding.
Install matching siding materials or trim boards to fill the gap at the sides of the window if necessary. Rather than nail in a row of little 6-in. siding pieces along the left side of the window (tacky, tacky), we removed the siding back to the corner and installed full-length siding pieces that butt to the trim board.
Window Shopping and Planning
We installed an 8-ft. 5-in. x 4-ft. 8-in. Pella Designer Series four-panel bow window. The approximate $3,000 price tag included grilles, extension jambs and flashings. Most major window manufacturers offer bow windows, available with three to seven panels, ranging in width from 6 to 14 ft., and in a variety of heights. Prices start at about $800. See the Buyer’s Guide.
Before placing your order, determine whether you can tuck the window under your eaves, like we did. Our 18-in. eaves easily accommodated and sheltered the 12-in. projection of our window. But if your house has narrow eaves or you’re installing the window on an unprotected section of wall, you’ll need a roof. Some manufacturers can put you in touch with a prefab roof supplier or provide design guidelines for experienced do-it-yourselfers to build their own. It’s a challenging job we don’t cover here.
Measure the combined thickness of your wall studs, exterior sheathing and drywall or other interior wall surface to determine the proper depth of your window’s extension jamb (Photo 8). A common thickness is 4-9/16 in.: 1/2-in. sheathing + 3-1/2 in. stud depth + 1/2-in. drywall + 1/16 in. of “play” = 4-9/16 in. Include this information when you order your window so the edge of the jamb will be even with the drywall, and your interior moldings will fit flat when installed.
The Interior Details
Use a wood shim to loosely stuff fiberglass insulation into the thin space between the extension jamb and rough opening. Hang, tape and sand the drywall, then paint it. Recut and reinstall the old interior moldings. If they’re not long enough or you’re completely redoing the room as we did, install new moldings (Photo 17).
We added a window seat with a hinged top for storage, as well as built-in cabinets to complete the project. This meant adding a 90-degree elbow to the existing floor heat duct and extending it through the face of the window seat. We left the old electrical outlets in the backs of cabinets to power the audio equipment inside.
You’re done. Take a bow.
Buyer’s Guide
ANDERSEN WINDOWS: (800) 426-4261. www.andersenwindows.com
CRESTLINE WINDOWS: (800) 552-4111. www.crestlinewindows.com
HURD WINDOWS & PATIO DOORS: (800) 223-4873. www.hurd.com
KOLBE & KOLBE: (715) 842-5666. www.kolbe-kolbe.com
MARVIN WINDOWS: (800) 435-0013. www.marvin.com
PELLA WINDOWS: (800) 547-3552. www.pella.com
WEATHER SHIELD: (715) 748-2100 or (800) 477-6808. www.weathershield.com
Advertisement 
