Setting a Gate Post in Sandy Coastal Ground
What the Footing Is Actually Resisting
A gate post is not mainly holding weight up. It is resisting being rotated out of vertical by a leaf hanging off one side of it, and that rotation is what a footing has to defeat. Understanding that changes how the hole is dug: depth gives leverage against rotation, diameter gives bearing area against soft ground, and the two solve different halves of the same problem.
Sand Offers Less Lateral Support
Firm cohesive soil grips the sides of a footing and contributes real resistance. Loose sand contributes much less, so the footing has to do proportionally more of the work by itself. In practice that means going deeper and wider than a general rule of thumb would suggest, and it means the shape of the hole matters. A hole belled slightly wider at the base resists being levered upward in a way a straight sided one does not.
The Water Table Is a Working Condition
Close to the water, a hole of any depth may begin filling before concrete goes in. Placing concrete into standing water dilutes it at exactly the point where strength is most needed. Pumping the hole out, or using a mix designed for wet placement, is the difference between a footing that reaches its design strength and one that never does. Discovering this at the pour is too late to plan around.
Drainage Around the Post
Water that collects at the base of a post keeps the surrounding ground saturated and keeps the steel wet where it enters the concrete. A footing crowned slightly above grade so water runs away, rather than dished so it pools, costs nothing at the time and removes the single most common corrosion site on an installed gate.
Curing Time Is Not Negotiable
Concrete gains most of its strength over days, not hours. Hanging a heavy leaf on a post the same afternoon loads the footing while it is still weak, and the small amount of rotation that happens then is permanent. The gate looks correct because it was trued while being hung, and it is already out. Waiting is unglamorous and it is the cheapest quality step in the whole job.