Advantages of Precast Stairs and Landings Industry Leaders We Work With Building Systems Types of Stairs JJ Hook Barrier Traffic Safety Products Other Precast Products Quality Request a Sample Installing a Stair Galleries Links	Attached Top or Bottom Landing (Half Z)   Attached top or bottom landings can be used in applications when there is no support for a landing. The bearing is at the ends. Half Z's range in thickness from 8 to 12 inches. However attached bottom landings can not be any more than 11 inches thick.