It is also desirable that the bottom of a siding course be
flush with the underside of the window sill. However, this may not always
be possible because of varying window heights and types that might be
used in a house.
One system to determine the siding exposure width so that it is about
equal above and below is described below:
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Divide the overall height of the window frame by the approximate recommended exposure distance for the siding used (four inches for six-inch-wide siding, 6 for 8-inch siding, 8 for 10-inch siding, and 10 for 12-inch siding).
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This will result in the number of courses between the top and the bottom of the window.
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For example, the overall height of our sample window from the top of the drip cap to the bottom of the sill is 61 inches. If 12-inch siding is used, the number of courses would be 61/10 = 6.1, or six courses.
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To obtain the exact exposure distance, divide 61 by 6 and the result would be 10 1/6 inches.
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The next step is to determine the exposure distance from the bottom of the window sill to just below the top of the foundation wall. If this is 31 inches, three courses of 10 1/3 inches each would be used. Thus, the exposure distance above and below the window would be almost the same.
When this system is not satisfactory because of big differences in the two areas, it is preferable to use an equal exposure distance for the entire wall height and notch the siding at the window sill. The fit should be tight to prevent moisture entry.
Siding may be installed starting with the bottom course. It is normally blocked out with a starting strip the same thickness as the top of the siding board.
Each succeeding course overlaps the upper edge of the lower course. Siding should be nailed to each stud or on 16-inch centers. When plywood or wood sheathing or spaced wood nailing strips are used on nonwood sheathing, sevenpenny or eightpenny nails (2 1/4 and 2 1/2 in. long) may be used for 3/4-inch-thick siding.
However, if gypsum or fiberboard sheathing is used, the tenpenny nail is recommended to penetrate the stud. For 1/2-inch thick siding, nails may be 1/4 inch shorter than those used for 3/4-inch siding.
The nails should be located far enough up from the butt to miss the
top of the lower course of siding. This clearance distance is usually
1/8-inch. This allows for slight movement of the siding due to moisture
changes without causing splitting. Such an allowance is especially required
for the wider sidings of 8 to 12 inches wide.
It is usually good practice to avoid butt joints whenever possible.
Use the longer sections of siding under windows and other long stretches
and use the shorter lengths for areas between windows and doors. If
unavoidable, butt joints should be made over a stud and staggered between
courses as much as practical.
Siding
should be square-cut to provide a good joint at window and door casings
and at butt joints. Open joints permit moisture to enter, often leading
to paint deterioration. It is good practice to brush or dip fresh-cut
ends of the siding in a water-repellent preservative before boards are
nailed in place.
The method of finishing wood siding or other materials at exterior corners
is often influenced by the overall design of the house.
A mitered corner effect on horizontal siding or the use of corner boards are perhaps the most common methods of treatment.
Mitering corners of bevel and similar sidings, unless carefully done to prevent openings, is not always satisfactory. To maintain a good joint, it is necessary that the joint fit tightly the full depth of the miter. It also is good practice to treat the ends with water-repellent preservative prior to nailing.
Metal corners are perhaps more commonly used than the mitered corner
and give a mitered effect. They are easily placed over each corner as
the siding is installed. The metal corners should fit tightly without
openings and be nailed on each side to the sheathing or corner stud
beneath. If made of galvanized iron, they should be cleaned with a mild
acid wash and primed with a metal primer before the house is painted
to prevent early peeling of the paint. Weathering of the metal also
will prepare it for the prime paint coat.
Corner boards of various types and sizes may be used for horizontal
sidings of all types. They also provide a satisfactory termination for
plywood and similar sheet materials. Corner boards are often made of
1 1/8- or 1 3/8-inch thick material. Plain outside casing commonly used
for window and door frames can be adapted for corner boards.
When siding returns against a roof surface — such as at a dormer
— there should be a clearance of about 2 inches. Siding cut tight
against the shingles retains moisture after rains and usually results
in peeling paint. Shingle flashing extending well up on the dormer wall
will provide the necessary resistance to entry of wind-driven rain.
Here again, a water-repellant preservative should be used on the ends
of the siding at the roofline.
Interior corners are butted against a square corner board of nominal
1 1/4- or 1 3/8-inch size, depending on the thickness of the siding.