ENLARGING THE GROUND FLOOR -- Framing and Fitting the Window

The opening you must cut through a wall to accommodate a walk-in bay window is framed like the opening for a doorway—reinforced studs at the sides support a header that spans the opening. All the tools and materials you’ll need for this work are listed

- Two Kinds of Wall: Nonbearing walls, which support little weight, usually have a single top plate and run parallel to the floor joists. In order to create a bay-window opening in such a wall, simply knock out the wall studs in the rough opening with a maul.

Bearing walls hold a house up. Typically, they have double top plates and run at right angles to the floor joists. Before cutting into a bearing wall, erect temporary shoring between floor and ceiling. For a second-floor bearing wall, erect shoring on the ground floor as well.

If you are uncertain whether a wall is the bearing or nonbearing variety consult a structural engineer or an architect. Or consider every wall to be a bearing wall and, before cutting a hole in it, shore up the ceiling.

- Bridging the Opening: Headers are usually made of laminated veneer lumber (LVL), which has largely supplanted ordinary lumber for this purpose. LYL is sold in the thickness of joist lumber, and two pieces can be nailed together side by side like joist lumber to double the thickness.

To get LVL that is strong enough for your purpose, you will need to tell the dealer the width of the window opening, whether the wall is a bearing wall, and what floor it’s on. High roof loads—heavy snowfalls or a rooftop deck or air conditioner — are also a factor.

CAUTION---Dust from lead-based paint or asbestos-laden materials once used in building walls can be hazardous. Follow the advice given earlier before cutting a bay-window opening in a wall.

AN OPENING IN A PLATFORM WALL

1. Shoring the ceiling.

• Cut four 2-by-4s 4 feet longer than the width of the rough opening. Nail two of them together as a sole plate and lay it on the floor 4 feet away from the wall.

• The third 2-by-4 forms part of a top plate. Set it next to the sole plate and mark both pieces for studs at 16-inch intervals.

• Cut studs 6 inches shorter than the distance from floor to ceiling, nail them to the top plate, then use the fourth 2-by-4 to double the top plate.

• With a helper, lift the assembly onto the sole plate , and shim between the ceiling and the top plate.

• Plumb and toenail the studs, beginning with the end studs. Then fasten a 1 -by-4 brace diagonally across the studs with 2- inch dry-wall screws.

• Remove the studs in the rough opening.

DOUBLED TOP PLATE; END STUD; DOUBLED SOLE PLATE

2. Installing king and jack studs.

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• At the marks that you made on the sole plate at each side of the rough opening (Step 1), lay out positions for two jack studs and one king stud.

• Cut two king studs to fit between the top and sole plates in the exterior wall, then cut four jack studs long enough to reach from the sole plate to the bottom of the header.

• Nail the jack studs together in pairs, then nail a king stud to each set with two 3.5-inch nails every 16 inches.

• Position the assemblies in the wall, and toenail them to the sole plate and top plate.

3. Assembling the header.

• Cut two lengths of LVL to fit between the king studs.

• Nail them together from both sides with 3.5-inch nails driven every 10 inches in a zigzag pattern.

4. Installing the header.

• With a helper, set the completed header on top of the jack studs. (For clarity, the shoring has been omitted from this drawing.)

• On each side of the opening, drive six 3.5-inch nails through the side of the king stud into the end of the header.

SOLE PLATE; KING STUD; LOCATION.

AN OPENING IN A BALLOON WALL

1. Supporting the studs.

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• Cut a 2-by-8 board about 4 feet longer than the width of the rough opening for the window.

• While your helpers hold the board—which is called a whaler— against the studs and the ceiling, tack it to the studs with double-headed nails.

• Secure the whaler firmly to each exposed stud with a 3/8” by 3” lag screw placed about 2 inches above the bottom of the whaler.

• Lay 2-by-8 pads on the floor beneath the ends of the whaler.

• Cut two 4-by-4 posts to fit between the whaler and the pads and install a post at each end of the whaler.

• Shim the posts tightly against the whaler and toenail them to both the whaler and the pad.

• Erect temporary shoring as shown.

• Measuring from the floor, mark the height of the header on the studs inside the rough opening, and cut them there with a saw. On the ground floor, pry the studs free of the sill plate and floor joists; for a second-story bay window, cut them level with the tops of the floor joists.

2. Installing the header.

• Shorten four of the studs re moved in Step 1 by the depth of the header. (For clarity, the shoring has been omitted from this drawing.)

• At each side of the opening, nail two of these boards as jack studs to a wall stud. Then toenail the jack studs to the sill plate or joist if one is in the way .

• Build a header (Step 3), and install it on top of the jack studs.

3. Completing the rough opening.

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• Cut four studs to the same lengths as the jack studs prepared in Step 2.

• Nail the studs together in pairs.

• Align the doubled studs with the rough opening marks you made on the floor, and toenail the tops to the header.

• If you have extended perpendicular floor joists, toenail the bottoms of the doubled studs to the sill plate or joist as you did in the preceding step. If you have cut away parallel joists and installed new ones, toenail the studs to the header in the basement.

• Remove the whaler and toenail the header to each stud above it, then remove the shoring.

A KNEE WALL TO SUPPORT THE WINDOW

1. Assembling the knee wall.

• Remove the rest of the sheathing — and the sole plate in a platform- framed house—within the rough opening for the bay window.

• Mark and cut top and sole plates for the knee wall from 2-by-4s or 2-by-6s, adapting the method for cutting header-joist pieces shown, Step 2.

• Measure the opening between the header and the subfloor, then sub tract the height of the bay window. Cut knee-wall studs 3.5” shorter than this measurement.

• For the front wall, nail top and sole plates to studs, putting doubled studs at the ends of the plates.

• For the side walls, trim the house ends of the plates flush with the interior edges of the jack studs, as shown in the inset, and position end studs so they rest fully on the plates.

2. Installing the walls.

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• Set one side wall at the edge of the platform and nail through the edges of the top and sole plates into the jack studs, then nail the end stud to the jack studs. In stall the other side wall the same way.

• Set the front wall on the platform, align the end studs of the front and side walls, and nail the sole plate of the front wall to the front header joist.

• Nail the side-wall sole plates to the side header joists, and then nail together the end studs of the front and side walls.

• Staple insulation between the knee-wall studs, vapor barrier facing the interior of the bay, then sheathe the knee wall.

• If the window you are using is built to butt against sheathing, cut away a 1.5-inch strip of siding from knee wall to header on both sides of the window opening.

INSTALLING THE UNIT

1. Positioning the window.

• Remove the seat-board brace from the window.

• With one helper for every 3 feet of window width, tilt the unit and lift it onto the knee wall. Butt the brick- mold against the house wall, and center the window between the jack studs.

• Brace the unit in the opening with two 2-by-4s tacked to stakes in the ground and wedged against the window mullions.

2. Leveling the window.

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• With a level, find the high end of the front window.

• Two inches along the front knee wall from the high end, nail the window frame to the top plate of the front knee wall with 2.5-inch finishing nails.

• Level the frame with shims driven between the knee-wall top plate and the low end of the window frame .

• Nail the window to the knee wall every 6 inches, nailing through the shims.

3. Plumbing the window.

• Cut two 2-by-4 nailing blocks to the height of the bay window.

• Plane a bevel on the edge of each piece to match the angle of the bay.

• Fasten the blocks to the jack studs at the edges of the rough opening with 3.5” nails, leaving a gap of 0.5” between the bevel and the window-end jamb .

• Plumb the window by driving wood shims between the blocks and the end jamb, then drive 3-inch finishing nails through the end jamb and shims into the nailing block.

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Securing the headboard.

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• Wedge the window in place by driving wood shims between the headboard and the header every 8 inches.

• Nail through the head board and the shims and into the header.

• Fill any gaps around the window with insulation.

ADDING A READY-MADE ROOF

1. Marking the siding.

• Nail the precut drip cap to the top of the window, then have a helper assist in positioning the center section of precut roof sheathing between the drip cap and the wall .

• While your helper holds the triangular side pieces of sheathing in place, outline the sheathing on the siding.

2. Removing the siding.

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• Set the roof sheathing aside and cut through the siding along the outline with a circular saw.

• Saw as far as you can near the top of the window and then complete the cuts with a chisel.

• Working from top to bottom within the saw cuts, pry off the siding.

3. Installing rafters.

• At the top of the stripped sheathing, nail a 1-by-6 board to studs in the wall.

• Toenail precut hip rafters to the mullions and the 1 -by-6.

• Attach the two end rafters flat against the house wall and the top of the drip cap. Being careful not to nail through the headboard, nail them to the headboard, the hip rafters, and the header.

• Nail the remaining rafters to the 1 -by-6 and headboard.

• Staple insulation to the headboard, vapor barrier side down. Nail the sheathing to the rafters with 3.5-inch nails.

• With roofing nails, fasten the drip edge to the lower edge of the roof sheathing.

• Flash the roof, and cover it with roofing material as recommended.