What are the required concrete slab specifications for exterior unit installations?

• A. 4 inches thick, 3500 psi
• B. 6 inches thick, 2500 psi
• C. 2 inches thick, 2000 psi
• D. 8 inches thick, 4000 psi

Answer: (A)

Exterior unit installations sit on a concrete pad that must provide enough bearing and crack resistance while keeping costs reasonable. The standard requirement is a four-inch-thick slab with 3500 psi concrete. This thickness and strength reliably distribute the unit’s weight, handle typical loads, and resist weather-related stresses without unnecessary excess material.

Choosing a thinner slab, like two inches, risks cracking and inadequate support. A thicker slab or higher strength (for example, eight inches or 4000 psi) adds cost and effort without extra benefit for normal installations, unless site conditions or the equipment weight dictate otherwise.