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Figure 3-6.-Wood fiber roof decking at gable ends.
Exterior Trim

Builder 3&2 Volume 02 - Construction manual for building structures
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Table 3-3.-Lumber Sheathing Specifications and Estimating Factor Plywood  extension  beyond  the  end  wall  is  usually governed by the rafter spacing to minimize waste. Thus, a 16-inch rake (gable) projection is commonly used when rafters are spaced 16 inches OC. Butt joints of the plywood sheets should be alternated so they do not occur on the same rafter. DETAILS AT CHIMNEY AND VALLEY OPENINGS Where   chimney   openings   occur   in   the   roof structure, the roof sheathing should have a 3/4-inch clearance on all sides from the finished masonry. Figure 3-7 shows sheathing details at the valley and chimney opening. The detail at the top shows the clearances between   masonry   and   wood-framing   members. Framing  members  should  have  a  2-inch  clearance  for fire  protection.  The  sheathing  should  be  securely  nailed to the rafters and to the headers around the opening. Wood or plywood sheathing at the valleys and hips should be installed to provide a tight joint and should be securely nailed to hip and valley rafters. This provides a smooth solid base for metal flashing. ESTIMATING  SHEATHING  MATERIAL To figure the roof area without actually getting on the roof and measuring, find the dimensions of the roof on the plans. Multiply the length times the width of the roof, including the overhang. Then multiply by the factor shown opposite the rise of the roof in table 3-2. The result will be the roof area. For example, assume a building is 70 feet long and 30 feet wide (including the overhang), and the roof has a rise of 5 1/2 inches: 70 feet x 30 feet = 2,100 square feet. For arise of 5 1/2 inches, the factor on the chart is 1.100:2,100 square feet x 1.100=2,310 square feet. So, the total area to be covered is 2,310 square feet. Use this total area for figuring roofing needs, such as sheathing, felt underpayment, or shingles. Lumber  Sheathing To decide how much lumber will be needed, first calculate the total area to be covered. Determine the size boards to be used, then refer to table 3-3. Multiply the total area to be covered by the factor from the chart. For example,  if  1-  by  8-inch  tongue-and-groove  sheathing 3-7







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