(1) If spring or equivalent type buffers are not being used and rated speeds do not exceed 50 ft. per minute, solid bumpers shall be installed. Solid bumpers shall:

(a) Be built of wood or other suitable resilient material;

(b) Have the ability to resist deterioration from weather;

(c) Have sufficient strength to withstand, without failure, the impact of a descending car carrying its rated load or counterweight and traveling at 115 percent of its rated speed.

(2) Spring type buffers shall be installed when speeds exceed 50 ft. per minute. Spring buffers shall:

(a) Be built with a minimum stroke of 3/4 in. and with a maximum stroke of 1 1/2 in.;

(b) Not fully compress when struck by a car carrying its rated load or counterweight and traveling at 115 percent of its rated speed.

(3) Inclined private resident elevators are not required to have bumpers and buffers except when obstructions are encountered.