Cement-fiber panels are somewhat more water-repellent than plywood, but should be installed with the same care as plywood. Hardboard panels are often the least expensive option, but if they’re not kept well covered and with paint at all points, they’re easily damaged and soak up moisture like a proverbial sponge. Panels are typically available in eight- and 12-foot lengths. Longer panels may enable you to minimize the number of horizontal joints between panels. Either way, expect to spend about a day installing 1200 square feet of panel with a helper. Before you begin, cover the sheathing with building wrap and install trim boards and flashings. Editor’s tip: When measuring a panel to cut to the correct width, subtract 1/8 inch to account for any gap that must occur between panels. If you are cutting off the overlap side, measure from the face of the panel (not the underlap). Make a V-shape mark near each end of the cut, placing the tip of the V at the precise measurement. Hook the chalk line at one end and pull it taut so the line crosses the V marks at their points. Pick the line straight up and let go to create a straight line. Editor’s tip: Crosscutting panels with a circular saw leaves a splintered edge on the face. To avoid this, cut the sheet from the back. If you want to cut on the finish side, score the face of the panel with a utility knife just to the inside of the cut line, then cut with the circular saw. Editor’s tip: Nails should be driven into studs. Commonly, nails are placed six inches apart along the perimeter and 12 inches apart in the middle. Trim overlaps the siding. Use Z-flashing at any horizontal joints. Keep the panels six inches above grade and at least 2 inches away from concrete or asphalt stairs or walkways. Gaps may be prescribed where panels join at a shiplap joint and where plywood meets flashings.
