Wood siding how-to -- Part A -- Installing bevel siding
Figure A: Installation of bevel siding.
The minimum lap for bevel siding should not be less than 1 inch. The average exposure distance is usually determined by the distance from the underside of the window sill to the top of the drip cap (See figure A).
From the standpoint of weather resistance and appearance, the butt edge of the first course of siding should coincide with the top of the window drip cap. In many one-story houses with an overhang, this course of siding is often replaced with a frieze board.
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:
- 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).
- This will result in the number of courses between the top and the bottom of the window.
- 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.
- To obtain the exact exposure distance, divide 61 by 6 and the result would be 10 1/6 inches.
- 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 (See Figure A).
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 (see figure B). 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.
Figure B: Nailing of siding.
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. (See Figure A).
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.
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