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Enclosing a porch is easier than building an addition from scratch. Provided the original structure is sound, walling in the porch creates new living space you can heat in winter, cool in summer, and enjoy all year. Clearing the Porch: Before you start, check local building codes and acquire a permit if you need one. Then strip the porch as described below. For a porch with partial walls, consult an engineer before proceeding; you are likely to need temporary supports for the roof. Constructing the floor and Walls: The next step is to lay an insulated subfloor, a task complicated by the fact that most porch floors slope to drain off rain; you can compensate with framing as shown. If the existing floor is level wood with a space underneath, insulate the underside and cover the top with plywood. New exterior walls are built much like interior partitions, with only a few modifications. Completing the Job: Lightweight vinyl siding over a sheathing of asphalt-impregnated board provides a simple, attractive finish for the outside walls. You can cut vinyl siding with a utility knife or tin snips, but for a big job it's faster to use a circular saw with a fine-toothed blade, reversed for a smoother cut. Inside the new room, most of the remaining steps are familiar ones: wiring, insulating, applying wall board, and covering the subfloor. The only unusual task may be walling over a window opening — and even that job is straightforward carpentry. CAUTION Before tearing down the existing ceiling, trim, and siding, check for the presence of lead and asbestos. TOOLS:
MATERIALS:
SAFETY FIRST: Wear work gloves when handling pressure-treated lumber. Add goggles and a dust mask when cutting the lumber, dismantling the porch, or in stalling fiberglass insulation. Wear a hard hat when working with unsecured materials overhead. 118 Preparing the porch. • Tear down the ceiling and its trim with a pry bar. • Similarly remove the frieze boards, but leave the soffits and fascias. • Take out shutters, screens, screen sup ports, and railings. • With a handsaw, cut through the doorsill along the inner edges of the side jambs to the interior subfloor. Pull the sill out. If you plan to re-trim the door, pry off the exterior casings. • Take out any windows. Remove aluminum, vinyl, or wood siding from the wall inside the porch area with a circular saw and pry bar, making sure not to cut into the sheathing underneath. Take out rough stucco and the metal lath under it with a 2-pound maul and hacksaw. You can leave smooth stucco or other masonry in place, but add furring strips to which wallboard can later be attached. LAYING A LEVEL SUBFLOOR ON A SLOPING SLAB 119a 1. Attaching the ledger. • Prepare the concrete slab. • To make the new floor flush with the interior floor, measure from the top of the interior subfloor to the slab and subtract 0.5”. • Using 2” pressure-treated lumber of this width, or ripped to this dimension, cut a ledger the width of the porch area. • Set the ledger on the slab and attach it to the house wall with 3.5” common nails. For masonry walls, use 2.5” cut nails. If you do not want the floors to be flush, make the ledger no smaller than a 2-by-2. 119b 2. Putting up header joists. • With tin snips, cut strips of 5” aluminum flashing to fit between the ledger and corner post on each side of the porch and between each pair of posts on the porch front. • Lay the strips along the perimeter of the slab and fold 1 inch over the edge. • Hold a straight board on edge with one end on the ledger, and place a level on the board’s edge. When the board is level, mark the location of its bottom edge on the post. Do the same at each post. • Cut a header joist to fit between each pair of posts by measuring from the marks to the slab and ripping a 2” pressure-treated board to this width. • Stand each header joist on the flashing, keeping its outer edge flush with the outside edges of the posts, and toenail the board to the posts with 3.5” common nails. • Bend the inner sections of the flashing against the inside faces of the header joists. 120a 3. Laying sleeper joists. • Measure from the ledger to each corner post and cut 2” pressure-treated boards at least as wide as the header joists to make two band joists. • Cut enough intermediate sleeper joists for a 16” spacing, measuring for each from the ledger to the header joists or front posts. • Rip each joist to match the height of the ledger at one end and the header joist or post marking at the other end. • Toenail joists to the ledger and posts; butt-nail to the header joists. • Check the top of each joist with a level; plane off high spots and shim underneath the joist as required. • Where joists are less than 2.5” high, secure them to the slab with cut nails. Otherwise set 2-by-4 pressure- treated bridges between the joists and nail the bridges first to the joists, then to the slab (above). • Bend the inner part of the side flashing against the inside face of each band joist. 4. Finishing the subfloor. • Lay foil-backed insulation batts at least 3” thick between the joists, foil side up. • Cover the subfloor framing with 1/2” plywood. • To make the bottoms of the posts watertight, set a strip of aluminum flashing 10” long against each post so that it ex tends 1 inch below the framing and its ends overlap the adjoining header joist and band joist. Secure the top of the flashing to the post with 1” galvanized roofing nails. A VINYL-CLAD EXTERIOR 121a 1. Putting up new walls. • Adapt the procedures that are shown earlier to build wall frames— including window and door openings—in place, rather than assembling the frames and then raising them. Nail the top plates and sole plates to the ceiling and floor joists, respectively, then fit studs between them, doubling the end studs where the walls meet the house. • To sheathe the walls, cut asphalt-impregnated board to fit from the top of each wall frame to about an inch below the lowest point of the floor joists. Butt the sheathing against door and window openings and stagger joints to avoid four adjoining corners. • Attach the sheathing to the wall framing with 1.5” galvanized roofing nails, then install exterior doors and windows. 121b 2. Applying the starter strips. • Snap chalked lines about 1.5” above the bottom of the sheathing. Check at the front corners to make sure all the lines are at the same level; if not, adjust the lines until they are. • Cut a starter strip about 6” shorter than each line. If more than one piece is necessary along a side, plan for a *” gap between pieces. • With a helper, align the top of the starter strip’s nailing flange with the chalked line about 3” from the corner, letting the bottom edge extend below the sheathing. • Secure the strip with 1.5” roofing nails at 8” intervals. CAUTION: Vinyl trim and siding expand and contract with heat and cold; if they are attached too securely, the finished siding will ripple. Drive nails through the centers of nailing slots and leave the heads about 1/16” from the vinyl surface of horizontal pieces; for vertical trim, let the nailheads just touch the surface. 122a 3. Covering an outside corner. Next, put up an outside corner strip at each front corner, as follows: • Set a scrap section of siding on the starter strip and mark on the wall the position of the base of the siding. • Measure from the top of the sheathing to this mark and cut an outside corner strip to that length. • At a convenient height, drive a 1.5” galvanized nail through a nailing slot on each side of the strip. • Plumb the strip, then continue inserting nails on both sides at 12” intervals . • To prevent insects and debris from collecting inside the strip, insert open-cell foam in the top and bottom of the strip. 123b 4. Covering an inside corner. • Cut a piece of J channel the same length as the outside corner strip. • Keeping the nailing flange flush with the sheathing, butt the channel as close as possible to the house wall. • Plumb the strip with a level, then drive 1” roofing nails through the flange into the sheathing and stud behind it at 12” intervals. • Seal the joint between the channel and the wall with silicone-base caulking compound. 123a 5. Completing the trim. • At each window, cut undersill trim to the sill length and nail it under the sill. • Measure the top of the casing, add twice the width of the J channel’s nailing flange to the figure, and cut a strip of J channel to that length. • Add the width of the flange to the distance from the top of the casing to the base of the undersill trim. Cut two J-channel strips to that length. • Center the top strip above the window casing. Mark the lip at each corner of the casing. • Place each side strip against the window so that the end is flush with the undersill trim’s base. Mark the lip at the top corner of the casing and the top of the sill. • Miter the pieces at the top-corner marks at a 45-degree angle, only cutting through the lip. Below the sill mark on the side pieces cut off the raised part of the channel. • Cut and bend a tab at each end of the top strip as shown in the inset. • Make a corresponding notch in each side piece. • Secure the three pieces with 1.5” roofing nails, interlocking the tabs and notches. Cut undersill trim to fit along the top of each new wall, making it the same length as the starter strips below. With a helper, butt the lip of the trim against the soffit, level it, and nail the flange to the sheathing. If more than one piece is needed on a side, leave about inch between the strips. 6. Attaching siding panels. • Cut panels 4 inch longer than the distance between the projecting edges of two corner strips, or of a corner strip and J channel. • Fit one end of the first panel under the side trim’s projecting edge, lift it to hook the lip onto the base of the starter strip, then slide the other end under the edge trim. Secure it with nails driven at 16” intervals. • Seat and secure other panels similarly, hooking each into the groove of the pre ceding panel. To join two panels end to end, allow at least 1 inch for overlap and stagger the joints from one row of panels to the next. Full-length panels come pre-notched to accommodate joints; for a cut end, make a 2” notch yourself. For walls viewed primarily from one end, make sure the panel closer to the observer is the overlapping panel. 123a 7. Fitting to openings and edges. • Where a panel will meet a window or door, make two cuts from the edge of the panel to the de sired depth; place the cuts for a piece fitting under the sill to allow a 1/4” gap at each side. Score the panel lengthwise between the cuts with a utility knife. • Set a heavy ruler in side the score line and bend the panel over the ruler to break off the un wanted portion. • At the top of each wall, score and break off the upper edge of the top panel so that the panel ex tends inch under the lip of the trim. Spread clear silicone caulking under the lip of the trim, then slide in the panel. FINISHING THE INTERIOR 124b Refinishing a sheathed wall • Run new circuits to the room, including one for a baseboard heater if desired. Insulate the- walls and ceiling. • Close off windows in the enclosed section of the old house wall by nailing 2-by-4s inside all four sides of the jamb and toenailing a 2-by-4 between the top and bottom boards. Cover the opening with sheathing. • Inside the house, fill the window opening with a wallboard patch secured to the exposed framing. If the opening runs along stud edges, attach 1 -by-2s to the studs to provide nailing surfaces. To re-trim the door, make the top and side jamb flush with the sheathing by attaching 0.75”-wide wood strips ripped to the required thickness. Alternatively, replace the door by ripping out the jamb and in stalling a prehung unit. Finish the ceiling and the walls with wallboard. 125a Adapting a masonry wall. To hide a window recess, butt-nail 2-by-4 sleepers to the side walls of the opening, keeping the out side edges even with the masonry surface. Toenail two or more 2-by-4s between the sleepers to pro vide nailing surfaces for the furring strips. Inside the house, extend the cripple studs through the window opening with 2-by-4s before putting wall board over the opening. To wallboard over all or part of the masonry wall, install 1 -by-3 furring strips 16 inches apart. Attach the strips with 1 cut nails, driven into mortar joints. At the door, nail furring strips inside the recess to install wallboard over the masonry, then re-trim the door in the new room with quarter-round molding. To replace the door, rip out the jamb but leave the rough frame, and install a prehung unit. 125b WORKING WITH A WOOD-FLOORED PORCH: Not all porches have a concrete floor If your porch floor is made of wood, insulate it as follows, then frame, sheathe, and finish the walls as described in the preceding pages. First, prepare the porch as described. Then saw off the edges of the floor flush with the existing support frame if the floor joists are smaller than 2 by-8s, double them. For a floor that's level at the desired height, and over a crawlspace, cover the ground below with sections of 6 mil polyethylene, overlapped by about 6” and weighted down with bricks or stones To insulate under the porch push 6” thick batts between the joists, vapor barrier side up, and secure them with wire insulation supports . Nail a 0.5” plywood subfloor on top of the existing floor if you can't crawl under the porch you will need to pry up the floor planks. Lay the polyethylene through the joists onto the ground and staple insulation between the joists. Replace the planks and install the plywood. A floor that slopes or is lower than the height desired requires an insulated wood frame covered with plywood on top of the existing porch floor. Follow the techniques for installing a subfloor over concrete but use 3.5” nails to attach the joists. |
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