Core Drilled and Surface Mounted Posts

A gate post is only as good as what holds its base, and when the walk or driveway is already concrete, a metal gate installation in Carlsbad, CA uses one of two methods (the comparison metal gate installation carlsbad museum house on bloor keeps for each kind of slab) instead of breaking out the slab. Core drilling sets the post into the concrete; a base plate bolts it on top. Each suits a different load and surface.

Core drilling

A diamond core bit cuts a round hole a little larger than the post, deep enough to hold it upright. The steel post is set in the hole, plumbed, and the gap is filled with non shrink grout or hydraulic cement. The finished post looks like it grew out of the slab. Core drilled posts handle heavy swinging gates well because the load is spread down the full depth of the hole.

Surface mounting

A surface mounted post has a steel plate welded to its base. The plate is anchored to the concrete with wedge anchors or epoxy set bolts. It installs faster and leaves no deep hole, but the anchors take the full leverage of the gate, so the method suits lighter walk gates and fences more than heavy driveway leaves.

Checking the slab

Either method depends on the concrete. Thin or cracked slabs, common on older patios near Interstate 5, may not hold anchors or a core. The installer checks thickness at the edge and looks for cracks before choosing.

Water and corrosion

Water collects at the base of a post. On a core drilled post the grout is sloped away. On a surface mount the plate is sealed and the bolt heads coated. Near the Encina Power Station and the beach, salt air speeds rust at these joints, so galvanized posts and stainless anchors are common.

When neither works

A very heavy gate or a weak slab may need the concrete cut out and a new footing poured. The survey decides this before the gate is fabricated.