Clapboard Siding Picture
These steps given
by Colonial Sense will help you to either repair existing clapboards due to rotting or splitting or if you adventurous, reside an entire house by yourself

Clapboard Repair

The common problem with clapboard is that it tends to split or crack over time. If the split or crack is small, simply glue the boards back together again using the following procedure

  • Hold the split open with a chisel or pry bar while you inject exterior wood glue.

  • Place a 1" X 2" beneath the split to hold it closed while the glue sets. Fill the nail holes with wood putty

  • After the glue dries, remove the 1" X 2" and fill the nail holes, then anchor the repair with finishing nails above and below the split.

If the clapboards are warped or rotted beyond repair, the bad boards will need to be cut out using a backsaw. Once the boards are cut, then remove with a chisel or pry bar and hammer. Replace the damaged area with freshly milled lumber.

If you must start from scratch and reside an old house with clapboard, the following installation tips and techniques will guide you.

All Walls Must Be Weatherproofed

It is important to install wind barrier material which stops water infiltration during storms but still allows condensation to escape. The wind barrier is most effective if you take great care in covering the edges of the corners of the house and door and window casings. Tar paper or building felt was always the standard choice to cover over the sheathing. Today there are various brands of housewrap, a woven or spun bonded plastic such us Tyvek and R-Wrap. Although be careful with housewraps because of the water repellency. Contaminants degrade the water repellency of housewraps. Furring strips provide an air space to reduce the buildup of moisture. Also back-priming the clapboards helps to reduce the moisture.

  • Install the tar paper or housewrap over the entire area with staples spaced 12" apart, make sure you are hitting the exposed studs. If sheathing is already on the home, you need not worry about the studs. Make sure the tap paper or housewrap in placed underneath the corner boards.

  • Work the tar paper or house wrap into the bead of caulk with a thin, right angled scrap of wood. The result is a neat, square inside corner that seals barrier, sheathing, and trim all together. Don't let the caulk fill up the corner or the clapboards will not lay right.

  • Flash all horizontal features such as head casings atop windows and doors. Bend flashing over the water table so that it extends 1 inch up the wall. Secure the top edge of the flashing with 4d nails. The flashing ends should be overlapped no less than three inches, and seal joints with caulking. The water table is a horizontal trim running around the base of the building below the siding and not all houses have it. If your home has a water table, it provides an excellent level base for the first course of siding. If the building is out of level, it is best to align visually to what is already there.

Determining the Best Lay Out of the Courses

If you are replacing existing clapboards, then simply just mark where the butt of each clapboard meets the edge of the trim board. You can punch a small hole in the trim with an awl. Trace the existing clapboard and cut to size. If no clapboards are available, lay-out becomes much more involved. The methods listed below are often used to determine where clapboards should be placed. Measurements can be adjusted with the changing shape of the old wall.

  • Decide on a starting line, whether it is the water table or a chalk line guided by the tops of windows or the frieze board on top.

  • Make a storey pole which is a length of narrow board, often a 1" X 4" usually cut to a height of one storey which would have marks for heights of important features on the side of the house such as window sill heights, window or door headers, or any other discerning features. A wood furring strip about 1" X 2" will be fine but make sure it is as long as the wall is tall. Hold the storey pole vertically against the wall and beside the end against the reference line. Then position the pole aside of each window and door and mark the top and bottom of each on one face of the pole. Now you will be able to tell on the storey pole the differences in the vertical spacing of the doors and windows. The clapboard courses that you install would not look right if it didn't line up with the tops and bottoms of the openings. Study the marks until you can standardize the wall layout into three vertical sections: above the windows, within the windows, and below the windows. On another face of the pole lay out the section measurements. Then divide the sections into evenly spaced courses. You many need to adjust the spacing of the courses to meet section divisions, or you may need to redefine the sections slightly to get the courses to come out even. Once you have established the standard courses on the storey pole, use it to judge how much you will have to vary the layout. Place the pole against the wall at the side of each door and window, and check the top and bottom of the windows and doors, as well as the total height of the wall, to see if they line up with the course marks on the pole. Then transfer the standard course spacing from the storey pole to the edges of the trim boards. A storey pole is worth the trouble to make because you can test the layout of an entire wall before your clapboards are cut and laid.

  • Set the clapboard exposure. The exposure of each clapboard can be adjusted up or down by as much as 1/8" on 2" to 3" exposures and up to 1/4" on 4" exposures. The clapboard exposure in the past 200 years followed no strict rule. It was all determined by the maximum width of the board and the visual effect from the layout of the courses based upon the door and window dimensions. However, it is important to be lapped by at least 1 to 1 1/2" to be weathertight, and to nail two courses of clapboard together. This small adjustment will not be noticeable from one clapboard to the next. It will, however, make a difference in the overall look of the siding. You do not want to deviate from the visual effect of the original character of the house. Some walls can be clapboarded with a random pattern while others can have a regular course spacing. As you lay the clapboard courses, take a step back and frequently check to see if the layout is fitting in with the character of the house. Be willing to remove a few clapboards if the work doesn't look right. However, also trust your judgement; sometimes adding one more board will make the previously laid out work look fine. You can always cut, fit, and then just tack the clapboards in place. When you have several courses that look right, nail them down tight.

Clapboard Siding - Corner board on the Studebaker House, East Berlin, Pennsylvania
Corner board on the Studebaker House, East Berlin, Pennsylvania
Laying Out Corners

It is best to install the corner boards prior to laying any clapboard courses. Corner boards protect the corners of the house where rain can deteriorate the butt joints of the clapboard coming together. Mitered joints look professional and elegant but aren't as durable as other options, and the technique required laborious hand-fitting. Corner boards can be designed to appear the same width on both wall, or substantially wider on the main face to have a pilaster effect. During the Georgian and Greek Revival eras, corners were detailed into full blown pilasters and wood quoins.

  • Cut all the corner board stock to length, and nail the boards together. Space galvanized nails about 6 to 8 inches apart.

  • Lift the corner boards onto the house and attach securely. Make sure to drive nails into house corner studs, not just sheathing.

  • For interior corners, these are not as not nearly as involved as exterior corners. The interior corner is simply a 3/4" X 3/4" single strip of wood or the size you choose which is nailed in the corner first. Then the clapboards butt into the corner board.

Clapboard Siding Picture
Clapboard Siding Picture
Clapboard Siding Picture

Lay Up Clapboards

Some carpenters work from the top down because it is easier to lay out longer courses using machine made clapboards. It also produces an tighter lapping and better weathertight seal since the lower clapboard is wedged into the upper clapboard. Since the lower board is wedged in, it is possible to work alone. Although most carpenters continue to work from the bottom up.

  • Clapboard Siding - Beaded Clapboard butted into the door jamb of the Studebaker House, ca1790. Notice the double rosehead nails used on the courses of clapboards.
    Beaded Clapboard butted into the door jamb of the Studebaker House, ca1790. Notice the double rosehead nails used on the courses of clapboards.
    Door and Window Courses Need Aligned. For best visual effect, the clapboard courses must be aligned with the tops and bottoms of windows and doors. It will take patience to cut and fit the courses to get proper alignment. Temporarily tack clapboards in position at the top and bottoms of windows and stand back to see if they flow with the shape of the wall and adjust them if necessary. Then mark these section lines on the wall surface with a chalk line. With the position of these critical courses located early on, you can make final adjustments in the course spacing as you approach them.

Clapboard Siding Picture
Clapboard Siding Picture
Clapboard Siding Picture
Clapboard Siding Picture

  • Begin Laying Clapboards. The layout of the first board is critical since it is the base for all successful rows. Try constructing a jig that duplicates the lap over each course. The first course is laid to match the base line of the water table or wall. If there is variation in the base line, then the clapboards should follow suit, using short lengths where waves are tight. Snap a chalk line from the corner boards to establish a standard course that you can deviate from slightly. Position the first clapboard in a course, then scribe and cut it. Tack the board in place. Then lay the next clapboard in position, aligning the laps. If the end goes past a trim board, mark where it meets the trim and cut it out. A good method is to cut boards long by about 1/16" then scribe them to meet the edge of the trim exactly. With scarf-joint clapboards either work from left to right or the opposite, but not both. Sticking to one lay standardizes all the movements it takes to cut, fit and install the clapboards, and makes the work more efficient. Each scarf joint is fastened with a single nail, grabbing two boards. 6d galvanized cut shingle nails from Tremont Nail Company. Cut nails have blunt points that punch a hold in the wood and make splitting less likely-especially important with scarf joints. If you use wire nails, you can limit splitting by boring a pilot hole in the clapboard. Remember to stagger the joints every course at random intervals. Space these joints a minimum of 16" apart.

  • Fitting Clapboard Around Openings. After four or five courses are laid, take a step back and visually inspect your work. If any course work needs adjusted on the top or bottom of any openings, now is the time to start adjusting the spacing. To fit a clapboard at the bottom of a window you will need to cut a notch in it. If there is a siding groove in the bottom of the sill, the accuracy of the fit is not critical. Simply lay the clapboard in position under the window sill and mark the length of the notch. Make the notch deep enough to allow the clapboard to nest up into the groove. Then cut out the notch with a saw. If the sill does not have a siding groove, you have to carefully scribe the board to the bottom of the sill using the following procedure. While not always practical, scribing is usually the best way to locate cutouts. Just hold the board in place and mark. Where the tops of windows and doors do not align with course lines, the clapboards have to be scribed to fit around them. This fitting should take place well ahead of time because it will lower the clapboard, and the spacing of the clapboards that run up to it may need to be adjusted. First, lay the clapboard on top of the window or door cap. Next align the butt edge of the clapboard parallel with the section chalk line on the wall. Then, use a pair of dividers to scribe a line on the clapboard that is parallel to the cap. Use a saw and utility knife to trim away the waste, and tack the clapboard in place. Afterwards, check the standard course marks to determine if any adjusting is needed in the courses below.

Methods for Nailing Clapboards

There are three methods to nailing clapboards to the wall, each with a specific purpose.

The traditional method for hand-rived clapboards is the two course method. It seems to be the prevalent method for beveled siding in the 1800's and earlier. With this technique, nails are spaced 1/2 inch to 3/4 inch above the butt of the clapboard so that they also anchor the top of the board in the course below. Two-course nailing appears on houses with riftsawn clapboard. Carpenter references prior to 1915 have recommended this style of nailing.

Nailing through a single course is the method recommended in much beveled siding literature today. One nail is sunk into the upper clapboard a sufficient distance up from the bottom of the board to miss the lower clapboard. This method of nailing practice does not hold the width of the board captive in the event of expansion. Some argue this method increases the chances a board will split or cup. Single nailing is also seen on lapped, rectangular, weatherboard type siding where the boards are wide and fairly thick.

Blind nailing has been used as a historic technique to cover the look of any nail holes in clapboard. It has been used on some buildings with rived siding no wider than 4 1/2". With blind nailing, nails are driven 10 to 12 inches apart at the top of each board. The butt edge is left unattached with the result that no nails are left exposed in the finished job and nail heads are protected from the weathering. In many cases, though, the butts wound up being spot-nailed years later anyway to close gaps.


Make sure all areas around the door and window openings, the corner boards and the butt edges on all four corners of the house are caulked thoroughly. Paint is also recommended on both the front and back of the clapboards prior to installing. Although there are more than a few New England clapboard homes that have never been painted in their lifetime.

Source: Research and Text by Bryan Wright

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