What is pierin construction?

Installation is the core difference. A drilled pier is bored into the ground, a rebar cage is set, and concrete is placed in the open hole, so it is cast in place. A pile is a prefabricated member (steel, precast concrete, or timber) driven or pressed into the soil by a rig. Piers tend to be larger in diameter and fewer in number, while piles run smaller and are installed in groups tied together with pile caps.

Depth is set by the bearing stratum in the geotech report, not by a rule of thumb. Light commercial piers may bottom out around 10 ft to 15 ft, while shafts for heavy structures or weak soils can run 40 ft to 60 ft or deeper. Drawing depths are design estimates, the inspector confirms bearing during drilling, and that is why contracts carry unit prices per vertical foot for overruns and underruns.

A belled pier has an enlarged, cone-shaped base cut with a belling bucket to spread the load over a larger bearing area. Bells commonly flare to 2 to 3 times the shaft diameter and only work in cohesive soils stiff enough to hold the shape until concrete is placed. For takeoff, the bell adds concrete volume beyond the straight shaft, so quantify it separately from the bell dimensions on the pier schedule.