Installing Panel Siding

Nails should be driven into studs. Commonly nails are placed 6 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 6 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.

Prepare the walls as you would for other wood sidings by applying building wrap, applying self-stick flashings at the corners and around windows and doors, and installing metal flashings as required.

Prime the panel edges. This is a good idea even if the panels are preprimed because plywood edges are very porous. Keep a brush and primer handy so you can prime all edges after cutting.

Locate stud centers and mark them so they can be easily transferred to the panels prior to installing (Step 9). Use a level to strike a plumb line where two panels will join; marking with a lumber crayon (shown) will make the line easy to see.

Installation will be easier if you have a temporary ledger to rest the panels on. The ledger should be about 1 inch below the sill plate. To stabilize it, pound 2X4 stakes into the ground a few inches away from the foundation. Fasten the ledger to the stakes with screws, leveling it as you go.

Plan the locations of the sheets to avoid narrow slivers near the sides of windows and doors. If studs are not 16 or 24 inches on center, plan the layout carefully so all edge joints will fall over a stud. You will likely need to cut the first panel lengthwise. Measure and cut the overlap side. The underlap should extend beyond the stud so that you can nail through the overlap of the next piece.

Make a cutting guide for long, straight cuts. Drive screws to fasten a straight 8-foot-long 1X4 or 1X3 against the factory edge of an 8-foot-long piece of plywood that is at least 10 inches wide. Guiding the saw base on the 1X4, cut the plywood to make the cutting guide. Use the guide as shown in Step 8.

When cutting a large panel, support it with four long boards, two on each side of the cut line. This way the panel will not fall away and possibly crack when you finish the cut.

Clamp the cutting guide to the siding to be cut, aligning the cut edge of the plywood part of the guide with the chalk line. Cut the siding with a circular saw, guiding the saw base along the board on the cutting guide.

To mark for nailing, measure from a corner or the next panel to the centers of the studs. Mark the panel in three places to show where you will drive nails. If a stud is at or near a channel on the panel, you might not need to mark more than one place. (If your panels have no channels, you might choose to snap chalk lines.)

Inside corners are rarely straight. If the corner is wavy, cut the panel 1-1/2 inches wider than it needs to be, then hold it plumb and scribe a line along a 2X2 held against the corner. You will cover the corner with trim (Step 21), but a more accurate cut will seal better than a sloppy one.

Rest the sheets on the temporary ledger and check for plumb. The edge of the first sheet should be about 1/4 inch shy of the corner.

Drive nails so they are tight and flush but do not drive the heads below the surface. It may take some practice before you can consistently drive nails without marring the panel. If you are having trouble, use a nail set when striking the last blow.

The ledger is handy for sliding the panel into place. With some panels you might have to temporarily tack nails in the joint to produce a 1/8-inch gap. Check with your supplier; if you neglect this gap, the panels might buckle in humid weather.

Hold a panel at the correct height and against a window or other obstruction to mark for the horizontal part(s) of a cutout. Cut 1/4 inch above the flashing or window. Measure over from the other panel to mark the top and bottom of the vertical cut and snap a line between the marks. Again, allow for a 1/4-inch gap.

Use a circular saw to cut the lines just up to the corners, and use a jigsaw or handsaw to finish the cut.

Before installing panels above, apply metal Z-flashing that overlaps onto the tops of the lower sheets. Attach the flashing by driving nails along the top edge.

To measure for an angle cut, hold a level so that it's plumb at each side of the sheet and measure along the level.

Use 1/4-inch plywood spacers to create a gap between the bottoms of the upper panels and the flashing.

At a roofline, attach flashing and install the panels 1-2 inches above the flashing. Use a scrap of lumber as a guide to keep the gap consistent.

Assemble two 1X boards to fashion trim for an outside corner and attach.

Trim inside corners with a 2X2 or a 1X board ripped to 3/4 inch. Drill pilot holes to avoid splitting the wood.