Since colonial times, Americans have protected their houses from the weather with thin, overlapping wood planks known as clapboards. The siding, which got its name from the Dutch work klappen, “to split,” was originally hand-split from logs of white pine, hemlock, spruce, or cypress. Later, saws did the work, turning out miles of delicate, tapered strips less than an inch thick.
Today, clapboard siding comes in a variety of woods, widths, and lengths, as well as in such man-made materials as fiber-cement. But as far as This Old House general contractor Tom Silva is concerned, western red cedar is still the best choice for the money. “It takes paint easily, goes up faster than shingles, and as long as it’s installed properly and well maintained it can last the lifetime of the house,” Tom says. “It looks great, too.”
To estimate the amount of stock needed for a siding job, measure the height and width of all the walls to get the total square footage of the surface area. Then deduct the area of all the doors and windows. Take that measurement to the lumber yard, where, based on the width and exposure of the siding you want, they will determine the number of linear feet you need.
Weatherproof the walls
Slip 12-inch-wide splines of felt behind the corner boards and the side casings next to doors and windows. If there is no housewrap or trim on the house.
Locate studs by tapping across the wall with a hammer.
Snap vertical chalk lines at each stud location, typically every 16 or 24 inches.
Bend flashing over the water table so it extends 1 inch up the wall. Secure the top edge of the flashing at the studs with 4d nails. Overlap the ends of the flashing 3 inches, and seal joints with a paintable synthetic-rubber sealant.
Staple 12-inch builder’s felt above the water table so it covers the flashing.
Staple two 2-inch-wide strips over each stud line. This creates a breathing space and provides an escape route for condensation.
Hang the starter course
Using a table saw, rip 1 1/2 inches off the top of a clapboard for a starter strip. Prop its thickest edge 1/8 inch above the water table; secure it to every other stud with one 7d nail.
Line up the lower edge or butt edge of the first full-width clapboard so that it covers the starter strip and lies a hair above the water table. This is the starter course.
Apply sealant along the corner boards. Bed clapboard ends into it, leaving 1/16 inch space along the corner board.
An inch above the siding’s butt edge, drive in one 7d nail into each stud.
If clapboard isn’t long enough to span a wall, splice two together with a 45-degree scarf joint. Apply sealant to the ends, fit them together, and drive one nail through the overlapping board ½ inch to the side of the joint.
Make a swing stick
To ensure that the courses are evenly spaced, make a “swing stick” from a straight 1×3 at least 6 feet long. Starting at either end, make a series of marks along one edge, each equal to the clapboard’s exposure to the weather. For 6-inch siding, that’s 4 1/2 inches. Mark an arrow on the end of the stick where you began measuring.
On the wall, snap a chalk line even with the windowsill’s bottom edge.
Stand the swing stick upright on its arrow-marked end between the window and corner board. The end should be even with the bottom edge of the starter course.
If any mark on the stick aligns with the chalk line, simply transfer all the marks from the stick to the wall. If none align, tilt the stick toward the marks until one lines up with the chalk line. Transfer the stick’s marks to the wall.
Make a story pole
Take a length of clapboard as long as the wall is high. Hold it vertically and align one end with the butt edge of the starter course.
Transfer the marks from the wall to the clapboard. This is your “story pole.”
Place the pole it vertically alongside the corner board nearest the marks made from the swing stick, line up its end with the starter course as before, and transfer the marks onto the corner board with a pencil and square.
Repeat the process to create a matching set of marks on the opposite corner board.
Hang following courses
Apply a thick bead of sealant along the vertical juncture where the wall meets the corner board.
Push the ends of the second course into the sealant. Align the butt edge with the story-pole marks on the corner boards.
Nail the clapboard to the studs as in Step 3.
Follow the chalk line to align the butts. Stagger the joints as you work up the wall.
With a utility knife, notch the top of the board to fit beneath the window. (Save the scrap for Step 9.)
Fit siding around windows
After notching the siding to fit around the bottom of the window, apply sealant under and around the windowsill.
Carefully slide the notched piece of siding into place.
Nail the clapboard to the studs.
If more than one clapboard is needed to span a wall, snap a chalk line between the marks on the corner boards on top of the course being overlapped.
Join the clapboards with scarf joints as in Step 3.
Siding beside windows
Hold the swing stick near the window casing.
Align one mark with the top of the head casing. Swing the stick’s bottom to one side.
When a mark on the lower part of the stick lines up with the butt edge of the last installed clapboard, transfer the marks on the stick to the wall.
Transfer the marks on the wall to the story pole as in Step 4. Then transfer those marks to the side casing and nearest corner board. Repeat the swing-stick/story-pole process on the opposite corner board, then continue hanging siding.
Stick an 8-inch-wide piece of waterproofing membrane above the head casing. Extend it 2 inches past the casing on each side of the window.
Bend a 3-inch-wide piece of flashing over the membrane and the window casing so it overhangs by ¼ inch.
Fasten the flashing’s top edge with 4d nails.