3.4.5.6.Figure 1-32.—Types of framing anchors.Place the outside pieces between the insidetrimmers. Drive three 16d nails through thetrimmers into the headers. Mark the position ofthe tail joists on the headers (the tail joists shouldfollow the regular joist layout).Fasten the tail joists to the outside headers withthree 16d nails driven through the headers intothe ends of the tail joists.Double the header. Drive three 16d nails throughthe trimmer joists into the ends of the doubledheader pieces. Nail the doubled header pieces toeach other with 16d nails staggered 16 inchesOC.Double the trimmer joists and fasten themtogether with 16d nails staggered 16 inches OC.A pair of joists, called trimmers, is placed at eachside of the opening. These trimmers support the headers.The headers should be doubled if the span is more than4 feet. Nails supporting the ends of the headers aredriven through the trimmer joists into the ends of theheader pieces. Tail joists (cripple joists) run from theheader to a supporting wall or girder. Nails are driventhrough the header into the ends of the tail joist. Variousmetal anchors, such as those shown in figure 1-32, arealso used to strengthen framed floor openings.CrownsMost joists have a crown (a bow shape) on one side.Each joist should be sighted before being nailed in placeto make certain the crown is turned up. The joist willlater settle from the weight of the floor and straightenout. Caution should be exercised when sighting theboard for the crown. Some crowns are too large andcannot be turned up for use as a joist.SUBFLOORThe subfloor, also known as rough flooring, isnailed to the top of the floor frame. It strengthens theentire floor unit and serves as a base for the finish floor.The walls of the building are laid out, framed, and raisedinto place on top of the subfloor.Panel products, such as plywood, are used forsubflooring. Plywood is less labor intensive than boardlumber.Plywood is the oldest type of panel product. It is stillthe most widely used subfloor material in residential andother light-framed construction. Other types of materialavailable for use as subflooring include nonveneered(reconstituted wood) panels, such as structuralparticleboard, waferboard, oriented strandboard, andcompositeboard.Plywood is available in many grades to meet abroadrange of end uses. All interior grades are also availablewith fully waterproof adhesive identical with that usedin exterior plywood. This type is useful where prolongedmoisture is a hazard. Examples are underlayments,subfloors adjacent to plumbing fixtures, and roofsheathing that may be exposed for long periods duringconstruction. Under normal conditions and forsheathing used on walls, standard sheathing grades aresatisfactory.Plywood suitable for the subfloor, such as standardsheathing, structural I and II, and C-C exterior grades,has a panel identification index marking on each sheet.1-16
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