At each row of the installation the install crew will call out measurements to the crew member running the chop saw minus 1/8” for a top cap, 1/8” for a bottom cap, and 1/8” for a buffer pad totaling 3/8”.
Build your perimeter pedestal using the new perimeter top cap and base cap. Use top shims and ½ buffer pad same as if making a standard pedestal. Place the perimeter pedestal as close to the containment as possible for a solid support. The single spacer fin provides the same 1/8” seem as regular top caps. Perimeter pedestals are actually stronger than regular sets.
Always spec a buffer pad on a waterproof membrane. The buffer pad protects the membrane from wear and tear over the years. This is your insurance policy against a call back years down road.