Footings for a Cantilever Post

Three feet of concrete is the number people expect and it is usually not enough under the support post of a sliding leaf. The excavation figures listed at Pearland Sliding Gates Freesizer run deeper than that, because the clay under most of Pearland moves enough through the year to walk a shallow footing out of plumb.

The Load Is Sideways

A swing gate hangs off its post and loads it in bending toward the opening. A cantilever slide does something harder: the two roller assemblies pull one way when the leaf is closed and the other way when it is open, so the concrete footing resists a load that reverses every cycle. Reversing loads loosen soil around a shaft that a static load would not disturb.

Depth Against Diameter

Going deeper resists overturning far better than going wider, up to the point where the shaft is long enough to be gripped along its length. A common shape here is a shaft of modest diameter carried well below the zone where clay dries out in summer, with a belled base where the soil allows one.

Expansive Clay

Gulf coast clay shrinks in a dry August and swells after a storm, and the movement is vertical as well as sideways. A footing stopping inside that active layer is lifted and dropped with it. The gate then binds at one point in its travel, somebody adjusts a roller to suit, and next season it binds in the other direction.

Reinforcement and the Post Itself

A cage of bar rather than a plain pour, and the post set into the concrete rather than bolted to a plate on top of it. A plate with four anchors is quicker and is fine on a small swing leaf, but under the reversing load of a slide it is the connection that works loose first.

Curing Before Loading

Hanging hardware on green concrete is the other common way a good footing is spoiled. The pour wants several days before it takes the weight of a leaf, and longer in cool damp weather. That delay is the cheapest part of the whole job and it is the part most often skipped.