1. (a) Unless otherwise specified in subsection (c) or other provisions of this chapter, wood side rails for all ladders shall have a minimum dressed cross section of the following dimensions:

   	Dimension of side rails at center
   Full working length of ladder (feet)	Thickness (inches)	Depth (inches)
   Up to and including 19	1-3/8	2-3/4
   Over 19, up to and including 30	1-3/8	2-3/4
   Over 30, up to and including 38	1-3/8	3
   Over 38, up to and including 42	1-3/8	3-1/2
   Over 42, up to and including 45	1-1/2	2-1/2
   Over 45, up to and including 52	1-5/8	3-3/4
   Over 52, up to and including 55	1-3/4	3-3/4

2. (b) The dimensions of subsection (a) are based upon a 7/8 inch mortise, 1/8 inch gain, or equivalent for step attachments. Where the strength of side rails is reduced more than this by the step attachments or where it is desired to use a rail section, either dimension of which is less than that specified in subsection (a), the rail section shall develop an actual working stress for the wood listed in § 21.63 (relating to group three woods), not exceeding 1,600 pounds per square inch when computed by the following formula applying to rectangular sections:

   

   where

   P = pounds, which is the normal component on each rail of a load of 200 pounds at the center of the ladder, equally distributed between the rails, when the foot of the ladder is moved out of the perpendicular by 1/4 of its length.

   W = weight of ladder, in pounds.

   L = length of ladder, in inches.

   B = net thickness of each side rail, in inches (deducting depth of gain, if any, for flat treads).

   D = depth of side rail, in inches.

   d = diameter of hole drilled for rung (d³ shall be taken as not less than 0.67, regardless of the method of step fastening used).

3. (c) Wood side rails of ladders having cleat steps shall be not less than 3/8 inch greater in thickness and 1/2 inch greater in depth than is specified under subsection (a) of this section, but no such ladder shall be less than 1 5/8 inches thick and 3 5/8 inches in depth (2 by 4 inches nominal).
4. (d) Metal side rails when made of mild steel or wrought iron shall be not less than 9/16 of a square inch in cross section for lengths 12 feet and under, and not less than 3/4 of a square inch in cross section for lengths over 12 feet with a minimum thickness not less than 3/8 inch. These dimensions are based upon the removal of not more than 1/2 inch of material for the attachment of the steps. When more material is removed from the side rails for step attachments or when side rails are made of other metal or shapes, they shall have the same strength.
5. (e) Except as otherwise provided in this chapter, wood side rails shall not be spliced.

Cross References

This section cited in 34 Pa. Code § 21.21 (relating to wood side rails); 34 Pa. Code § 21.34 (relating to fixed ladders); 34 Pa. Code § 21.35 (relating to single or straight ladders); 34 Pa. Code § 21.36 (relating to extension ladders); and 34 Pa. Code § 21.40 (relating to stepladders).