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Tools: • Claw hammer • Crosscut saw • Power circular saw, stationary or portable • Framing square or combination square • Tape measure • Scratch awl • Drills (electric and hand) • Wrench • Carpenter’s level • Hacksaw • Chalk-line reel • Demolition equipment • Nailing gun • Lath knife FOR MOST CONSTRUCTION Nails: 6d (sixpenny), 10d, 12d, and 16d Joist stock, to be used for joists, headers, and trimmers. Specific dimensions and quantity are determined by examining the framing plan. Buy about 10 % more to compensate for damaged or warped lumber Plywood or plyscore for the subflooring Timber connectors and joist hangers FOR DEMOLITION and RECONSTRUCTION Materials If you are doing any new construction, and even if you are only framing an opening for a stair or a chimney, it's likely you will need some of the following: Most of the above and 2 x4, 2 x 6, and 4 X 4 Lumber (can be used) for shoring Read this entire section on the construction of a new floor system whether you are building an extension or cutting into an existing floor. Even if you have had a good deal of carpentry experience, the more you know about how a house is framed, the less likely you will be to make a dangerous and costly error. FOR CONSTRUCTION OF AN EXTENSION All of the above and 2 X 6 lumber, pressure-treated for the sills. Order enough lumber to go around the extension’s periphery twice. The lumber will inevitably have a consider able number of defects and some of it will have to be discarded. Sill sealer Bolt nuts (to fit over the anchor bolts) 1 1/4 X 4 rough-sawn lumber for the cross bridging or additional joist stock for solid bridging CONSTRUCTING THE FLOOR SYSTEM FOR AN EXTENSION Examine your framing plan to determine the direction of the joist span and whether you will require a girder. If you are framing between new perimeter walls, you need not disturb the existing house until most of the floor is completed. Follow the instructions below. If you are framing between the existing house and a new foundation wall, you will have to prepare the existing wall for the extension. Carefully mark off the length of the extension onto the existing siding and plan to remove the strip of siding and sheathing that's covering the existing header or trimmer. If you aren't sure of the depth of the existing header or trimmer, demarcate a strip about 10” high. Cut into the siding with a circular saw that's extended only to cut through the siding (you want to make sure you don’t cut through into the header). If your existing siding is clapboard, make sure you have a smooth, flat guide for the saw. Use a worn carbide blade and watch out for nails. Pry off the siding using a utility bar. Repeat the step for the sheathing. You will frame the joists into the now ex posed header (or trimmer) using joist hangers. Check the condition of the existing header and sill. If they are rotted, you will have to replace them. If the header consists of short pieces of lumber, you will have to remove and replace it. If the header isn't properly secured to the sill and the existing joists, make those connections. The new joists of the extension will frame into the existing header with joist hangers. The Girders A built-up girder is constructed out of three or more pieces of 2” joist material of appropriate depth. Remember that the joints between the segments of lumber must be staggered and should always be over a support. Line up the first three pieces of wood, sandwiching the shorter piece in between the longer ones. Nail the individual sections of the built-up girder together using 10d nails. Continue nailing on one side and , when complete, turn the sandwich over and nail the other side. It is important to nail the section together so that the girder acts structurally as one unit. The built-up girder (or solid section, depending on what is specified in your framing plan) must be set into the pocket framed in the foundations. This pocket should be 1” wider than the girder, and should have a minimum bearing surface of 4”. A small piece of roofing membrane is put on the bearing part of the pocket for absorption of moisture. When both ends of the girder are lying in their respective pockets, check to see that the girder is level, using the carpenter’s level. Corrections may be made (if you are off by only a few fractions of an inch) by wedging pieces of slate or metal between the girder and its support on the side that's low. When completed, the girder should be level (or should have a small camber upward) and should project about 11/2” above the foundation wall. If you have intermediate supports, connect the girder to the piers as shown in Illustration 3. You need not connect the girder ends to the pockets, as the flooring yet to come will provide adequate connection and stability. You are now ready to construct the floor. The Sill The sill is a pressure-treated, rot- and insect-resistant piece of lumber that's bolted to the foundation wall through predrilled holes. (The floor joists in turn will be nailed to the sill.) We must first cut all of the sill sections and drill the holes. Choose straight, clean, long pieces of sill material and , beginning at the corner of the foundation wall, lay the sill alongside the anchor bolts. Place the combination square’s handle on the side of the wood away from the bolts and transfer the marks as shown in Illustration 8. The anchor bolts will not be in perfect alignment with one another. Be sure to measure the distance from the outside of the foundation wall to each bolt and measure that same distance onto the lumber being used for the sill. Be sure that all of the sill sections butt each other squarely. Mark the sill sections and the foundation wall so that you will know where each section fits and remove the sill sections. Drill ¾”-diameter holes at the points marked. (Although the bolts are only 1/2” in diameter, drill a slightly larger hole to compensate for small miscalculations.) Notch the sill around the projection of the girder. * Be careful when working with pressure-treated wood. Wear gloves and consult your health department regarding the proper inhalation protection. When all of the sill sections are marked and drilled, replace the sections and make sure they fit. Once again remove the sill sections and position the termite shields, if you are going to use them. Apply the roll of sill sealer to the top of the foundation wall, snipping or puncturing the holes for the bolts. This material, normally 1” thick, will compress to approximately 1/8” or less when the joists are installed. The sill sealer will protect against insects, air infiltration, and dust. Reposition the precut, predrilled sill sections and check to see if they are level. If there are gaps, fill them with grout. Grout can be used to some extent to level the top of the foundation wall. When the grout is dry, apply the nuts and washers to the bolts and tighten. Check again for levelness. (Accommodations can be made to raise portions of the sill slightly by loosening the bolts and wedging slate scraps under the sill.) == == == TERMITE PROTECTION Most areas in the United States are subject to termite infestation. To prevent the invasion of these wood-eating insects: 1. Use pressure-treated sills, which resist insect damage and also protect against wet- and dry-rot damage. (Alternatively, use redwood heartwood or cedar heartwood.) 2. In the past termite shields were used extensively, but since the shield is one of the first elements to be installed after the foundation, it's subject to damage that tends to reduce its effectiveness. In theory, a termite or other insect would not be able to negotiate an un damaged termite shield. A series of dents or irregularities in the shield, however, would serve as a pathway for these wood chewers. Therefore, be very careful that you don't damage the shields when you backfill. Chemical treatment of the soil is the alternative to termite shields. Check with local building department and environmental authorities to find out which chemicals, if any, are considered safe and are permissible in your community. In addition, have a reliable exterminator install the chemicals. 3. In areas where termites aren't a major problem the careful installation of a termite shield may be considered a form of insect insurance. == == == Headers and Trimmers A section of joist called the header, which the rest of the joists will abut, is set on the sill. The last joist on either side of a run of joists is called the trimmer. Together and in conjunction with the sill they enclose the platform floor. Working flush with the exterior edge of the sill, toe-nail the header to the sill every 16” using 12d nails. Make sure that the sill and the headers are at right angles before nailing. Check the framing plan for special details, such as a cantilever, which may eliminate the need for a header in that location, before completing the work. When the sill turns a corner, be sure to nail the header to the trimmer. Marking Off the Joists onto the Headers The perimeter is complete and now we have to mark the location of the joists onto the headers. Study the floor-framing plan carefully. We will use the lap-joint detail for joining the joists over the girder (and we will hang the joists onto the existing house’s header at the other end of the span. The simplest way to mark the joists on the sill is to create a template (also called a story pole). To make a story pole, first find a very straight, long (about 8’) piece of lumber, then measure and mark off the exact demarcations with a tape measure and pencil. Using a combination square (or a framing square), draw lines across the width of the template perpendicular to the edge. The template will have evenly spaced markings 16” (or 12” or 24”) apart on it. It will be used when you have a clear run of joists without interruption. If you have special conditions, such as the doubling of the joist for a partition or to frame an opening, you can mark these special conditions with an X or a different- colored pencil. The next step is to transfer the markings from the template to the header. Measure 15 1/4” along the header from the corner where the header meets the trimmer. Then lay the template on the sill along the header and transfer the 16” demarcations onto the header. The reason that we first measured a 15 1/4” spacing is in anticipation of the installation of the subfloor. The subfloor material comes in 4’ X 8’ sheets. We want the end of the sheet to lie on the center line of the joist. Use the combination square as an aid in transfer ring the marks. On the side of the mark closest to the header draw an X. This X mark is a convention used by carpenters to indicate on which side of the mark the joist is to be set. The template may be used along the rest of the header, marking off the 16” demarcations. Most likely there will be some framing details, such as openings for stairs and the doubling of joists under partitions and bathtubs, that will interfere with this even line of joists. Check the framing plan. Mark the exact location of any additional joists onto the header. Transfer the mark onto the template using a contrasting-colored pencil. Be sure to draw an X indicating on which side of the line the joist is to be placed. Be sure to write the word “start” on the end of the template nearest to the trimmer, so that you will not be confused as to which end of the template is the beginning and which is the end when you start to mark the girder. To mark the girder, transfer the marks from the template onto the girder. When marking the adjacent row of joists (that go from the girder to the other foundation wall), remember that we are using a lap joint over the girder. The joists will not lie in exactly the same places as on the first foundation wall. Installing the Joists If you are using joist hangers, nail them to the header so that the top of the joists will be level with the top of the header. Select the joist lumber. If the joist is to lap over the girder, the exact length isn’t important as long as the end sits completely over the girder. The squareness of the cut isn't crucial either; that's the advantage of this joint. (If you are using a butt joint, rather than lapping over the girder, or if you are spanning between headers, it's necessary to measure and cut the joists precisely.) When cut ting the joists or any other members that must be cut in multiples, be sure to cut only one or two pieces first to make sure that they fit. Set the joist on the sill and on the girder (or in the joist hangers, or on the opposite foundation wall). If the joist has a slight camber (desirable) set it with the convex side up, as the weight of the floor will rectify the camber. Be sure that the joist is right on the line that was so painstakingly marked with the combination square to ensure its being perpendicular to the sill. Nail the joist to the header with three 20d nails. Framing an Opening Check the framing plan for the exact size and location of the opening. Install the run of joists on either side of the opening, leaving out the joists that will span the opening and the joists on either side (otherwise there will be no room to swing a hammer). Install the inside trimmers first just as you would ordinary joists. Mark the location of the four header joists on the trimmers. Cut the header joists to size and install the outside headers. Finally, install the outside trimmers, the crippled joists, and the inside headers, in that order. The stability of the entire system depends on the accuracy of your measurements and on the squareness of the joists. If the length of the opening isn't running parallel to the line of the joists, care should be taken to beef up the nailing at the junction of the headers and the trimmers. If the opening is particularly long (over 10’), you may want to triple the header and triple the trimmer. The section should be calculated as if it were a girder. Installing the Bridging and Subfloor Although wood cross bridging is more economical of material than solid bridging, it's much less economical of labor. In cross bridging, the cutting and temporary nailing are done before the sub- flooring is applied; the final nailing, however, must wait until the subfloor is completed. This is difficult to do in a crawl space. Solid bridging (for which scraps are used) may be constructed before the subfloor. Measure and cut each piece of bridging so that it exactly fits the joist space. Stagger the bridging to simplify nailing. Be sure to align the tops of the joists. A third alternative is to use metal cross bridging, which is easiest since it's precut and pre-drilled. Plywood subflooring 5/8” or 3/4” thick is laid with the grain of the outer plies at right angles to the joists. Subflooring is nailed with 10d nails (a better choice may be barbed, screw-type, or resin-coated nails) to each joist every 6” along the edges of the panel and every 10” for the intermediate joists. Constructing the Second Floor The second floor or any subsequent floor or balcony is constructed in much the same way as outlined above. The difference is that the header and joists are nailed to the top plate of the wall rather than to the sill. MODIFYING THE FLOOR OF AN EXISTING HOUSE It is likely that you will want to cut into the existing floor for a stair or chimney. If you have a choice, make the opening so that its length is parallel to the run of the joists. For a stair or similar opening, first expose the structure on the underside of the floor by removing the existing ceiling. If the ceiling is gypsum board, the size of the opening will determine the tool you use to make the cut. For a small opening, use a keyhole saw. For a larger opening, start at the joint and , using a lath knife, cut through the tape and spackle and remove the whole piece. With a pencil, draw the outline of the opening on the underside of the subfloor. Construct shoring, which is (more or less) a temporary wall that will support the lines of joists on either side of the projected opening. Shoring can be constructed out of 4 X 4’s spaced about 2’ apart, with 2 X 4’s used for the double top plate and the bottom plate and as diagonal reinforcement. These temporary supports may be constructed in sections that are tilted up, leveled, and tightly wedged or shimmed into place. (In an old building that's not level, it's best to build the shoring in place, so that it's properly secured.) Shoring should be securely nailed to the joists to ensure that it will not slip out. Refer to “Framing an Opening”. Install the inside trimmer joists that will frame the opening. Cut and remove the center portion of the joists and install the outside headers, nailing them to the crippled joists. Install the out side trimmers and the inside headers, nailing all securely. Slip joist hangers from the bottom. Finally, cut through the subfloor and the finished floor. Next: Constructing and Modifying the
Walls and Partitions |
