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. A garage attached to the house offers an excellent opportunity to expand your home’s living area. Because they are de signed to bear the weight of automobiles, garage foundations generally require no reinforcement for a second-story addition. And since the garage is walled off from the interior of the house, you can proceed with construction without disrupting your family’s daily routine. - Planning the Job: Before you begin, carefully diagram all the details of your design. Decide, For example, whether you want an interior stairway, as this will affect how you lay the new floor. Rather than add stairs, you could choose instead to cut an entryway from the second floor of the house. If the top plates of the house and garage don’t align, simply incorporate a step, with a handrail on each side, between the levels. - Supporting the New Floor: The ceiling joists of a one-car garage typically span no more than 12 feet. If the joists are 2-by-8s or larger and are set no more than 16 inches apart, or are I-beams, they will support a second story as is. Otherwise, you must reinforce them. The structural requirements for adding a room over a two-car garage are more stringent. Usually about 24 feet square, a two-car garage has a span that is too great for lumber floor joists. The best solution is to support the second story on I-beam joists. Also use I-beam joists in a one-car garage if the existing roof is constructed with prefabricated trusses, since there are no ceiling joists to reinforce. In either size garage, if the joists rest on the wall where the doors are located, the door openings must be framed with strong headers. - Recycling Materials: If removed carefully, the structural members of the existing garage roof can be used to cap the new addition. See earlier section for framing a roof with rafters and a ridge beam for installing trusses. CAUTION --- A Before removing or cutting into walls and roofs, check for asbestos and lead. TOOLS:
MATERIALS:
SAFETY TIPS --- Goggles will protect your eyes from flying debris while you are hammering. Wear a dust mask and earplugs when you are using a power saw. Don a hard hat while removing or installing rafters and roof trusses. 88 REMOVING THE ROOF Stripping the shingles. 89a--- • Starting at the peak of the roof and working down each side, slide a flat shovel or shingle ripper, available from hardware stores, under each shingle to pry up the nails. • Remove the shingles, then strip away the flashing and layers of building paper to expose the sheathing. To take down a truss roof, follow the procedures listed at the top of the next page. If you have a traditional rafter and ridge-beam roof, use the instructions at the bottom of the next page. CAUTION --- When working on your roof, observe the safety measures described. = Tricks of the Trade -- Collecting Roofing Debris = 89b--- You can minimize the mess in your yard and protect siding and garage doors with a catchall for shingles and other materials tossed from the roof. Nail together three 2-by-4s and lean them against the garage below where you will be working. Tack on a sheet of clear or white plastic long enough to cover the frame and extend at least 10 feet into the yard or driveway. 89 Taking down a truss roof. 90a--- • With a pry bar, start at one end of the roof and pry up just enough sheathing to expose a maximum of three trusses. Then remove the siding and the sheathing from the gable. • To lift off the end truss, first pry out the nails fastening it to the top plate of the wall and to framing anchors at both ends, then lower it to helpers on the ground. • Remove the next two trusses, then nail diagonal 2-by-4 braces to the exposed top plates to steady the walls and corners of the garage. • Take off the remaining sheathing and trusses in stages, resting the trusses on top of each other over the diagonal bracing until you are ready to lower them to the ground. Removing rafters and a ridge beam. 90b--- • Starting at the top, pry up the first row of sheathing bordering the ridge. Work down, re moving the sheathing in horizontal courses. Then pry oft the siding and sheathing from the gable. • Attach a temporary support near each end of the ridge. If the beam is jointed, install an additional support on each side of the joint. • Pry the rafters loose from the ridge beam, ceiling joists, and top plates and lower them to the ground. Remove the end rafters and gable studs. • Lift the ridge beam from its temporary supports and lower it to the ground. In a one-car garage, leave the ceiling joists in place; in a two-car garage, remove them and brace the corners of the garage with diagonal 2-by-4s, as with a truss roof. 90 DOUBLING EXISTING JOISTS 91a--- 1. Trimming the old joists. If you have a one-car garage with 2-by-6 joists, double them to sup port the new floor, as follows: • With a handsaw or reciprocating saw, cut the ends of the ceiling joists 1.5 inches from the outer edge of the top plates; pull any nails that might interfere with the saw blade. • Cut header joists from 2-by-6 lumber, and install them in the space you have cleared along the outside edges of the top plates. 2. Attaching the new joists. • Cut 2-by-6s to fit between the header joists, and position them alongside the old joists. The tops of the new joists and the old joists must be flush. Insert wood shims between the new joists and the top plate if necessary to align them. • Using 3.5-inch nails, secure the old and the new joists to each other, then nail the new joists to the top plates and header joists. If your joists are more than 16 inches apart, install additional doubled joists between them. 91 SPANNING A TWO-CAR GARAGE Laying out I-beam joists. 92a--- • Frame the doors of the garage. • Double the existing top plates on the garage walls. • Toenail header joists to the top plates of the two bearing walls with 3.5-inch nails every 12 inches. • Place a band joist on the top plate of the end wall and nail it to the ends of the header joists. Then toenail it to the top plate every 12 inches. • Place another band joist against the common wall and nail it to the header joists, then toenail it to the top plates of the two walls. • Install I-beams, at least 1.5 inches deep, every 16 inches. Have a helper steady the beam while you drive 3-inch nails through the header joists into the top and bottom flanges on each side of the web, then drive 3.5-inch nails, at least 1.5 inches from the end of the I-beam, through the bottom flange and into the top plate on both sides of the beam. I-BEAMS FOR A GREATER SPAN 92b--- A second-story addition over a garage often occupies an unsupported floor space wider than 18 feet— the longest distance that a 2-by 12 lumber joist can safely bridge—but you can solve the problem by using I-beam joists. Even in a shorter span, you might consider substituting I-beams for lumber joists because of their more consistent size and quality and lighter weight. Composed of two flanges of laminated wood that are joined by a 0.5-inch or 3/8-inch web, I-beam Joists are strong enough to span long distances without any intermediate support. The I-beams used in residential construction are made to order, and are available from most building suppliers, you should allow at least 3 weeks for delivery. 92 THE UPSTAIRS FLOOR AND WALLS 93a--- 1. Installing the subfloor. • Beginning at one side of the garage, lay a row of 5/8-inch tongue-and-groove plywood sheets lengthwise across joists, with the grooved edge toward the opposite wall of the garage. • If necessary, cut the plywood so that the end joints of each sheet rest on the joists. Leave a 1/8-inch space between sheets for expansion. • Check the fit of the first row. Then lift off the sheets, apply construction adhesive to the tops of joists, and position the sheets on the joists. Drive 2-inch nails through the plywood into the joists at 6-inch intervals. • Staggering the end joints, lay successive rows by inserting the tongue of each sheet into the groove of the sheet already in place. 2. Raising second floor walls. 93b--- • Haul materials up to the finished subfloor and use it as a work platform to build sections of second-story walls. • Nail 2-by-4 stops against the outer surface of the header and band joists. • Raise each framed wall section into place against the stops, tilting it up with 2-by-4s hinged by one nail to the middle and end studs. • Plumb and level the wall section, and then brace it in place by nailing the free end of the 2-by-4s used for tilting to a short 2-by-4 block nailed to the subfloor. • Follow the procedures shown to secure the wall sections to one another and to the existing house. |
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