to overlap the J-channels by 3/4". Horizontal Siding Installation Installing Panels The first course (row of panels) should be placed in the starter trim and securely locked along the entire length of the siding panel. Make sure the panel is securely locked before fastening. Fasten the panels in the center of the nailing slots. Allowance should be made for expansion and contraction by leaving a 1/4" gap between the siding and all corner posts and channels (increase to 3/8" when installing in temperatures below 40 F. If the panels are 20 feet or longer, increase the gap to 3/8". Do not drive the head of the fastener tightly against the nail slot. Leave 1/32" between the fastener head and the vinyl (about the -thickness of a dime). Do not force the panels up or down when fastening. Panel locks should be fully engaged; however, the panels should not be under vertical tension or compression when they are fastened. Since vinyl siding moves as the temperature changes, make certain that the vinyl panels can move freely in a side-to-side direction once fastened. When panels overlap, make sure they overlap by one half the length of the notch at the end of the panel, or approximately 1". Stagger the siding end laps so that no two courses (rows of panels) are aligned vertically, unless separated by at least three courses (rows of panels). Always overlap joints away from entrances and away from the point of greatest traffic. This will improve the overall