Posts for Automatic Gates should be either Galvanised Steel concreted firmly into the ground, core filled brick or concrete block with suitable reinforcing steel into a suitable concrete footing or seasoned hardwood 150mm square or diameter either concreted or rammed into the ground firmly.
A Swing Gate should not be able to drop and drag on the ground as this will cause problems. A sliding gate must remain lined up with guides and not jam.
If you have existing posts in good condition but are bending a little with the weight of a swing gate the posts can be braced rather than replaced.
Bracing Swing Gate Posts.
A fence panel attached to the post in line with the closed gate
Will brace the Gate Post significantly but only when the gate is closed, it will have little effect when the gate is open. To brace the open position a metal or timber compression brace can be used (see below).
A Wire as a tension only Brace
Must be secured firmly into the ground using a metal or timber post concreted into the ground. Will blend in behind wire fencing but is only suitable for bracing the post for the closed gate position. See fencing suppliers for wire and fittings.
Galvanised Pipe as a tension and compression brace
This must be concreted securely into the ground. Can be used within a front fence line for the gate closed position and a second pipe parallel with the open gate to brace the open position. See Fencing Suppliers for pipe, pipe bending and fittings.
Do not use a wheel to support the weight of a gate
as this can make a gate difficult to open and close and is not suitable for automation.
DO NOT Fill a steel post with concrete
It can stiffen it up considerably but makes it very difficult to drill into and run cables inside for installation of an automatic operator.
Installing a gate post
If the ground is hard you need to dig a hole 100mm wider than the post, then put a small amount of concrete mixed quite dry (less water than normal) into the hole followed by the post and more dry mixed concrete rammed around the post checking the plumb from both sides as you go with a spirit level.
You won't need any temporary bracing for the post as the rammed in concrete mixed quite dry will hold it in place and won't shrink much as it sets. You just need to stop anyone from leaning on the post for a few hours until the concrete is hard enough. Allow a week or two for the concrete to harden up property before hanging a gate.
If the ground is very wet, sandy or soft the post must go much deeper preferably into drier and harder ground below. If the ground is still soft 1m down then make the hole larger at the bottom and add lots of concrete. The top must have a wider area of concrete or be hard against a concrete driveway. Do not use drainage gravel around a gate post to drain it, as this can move around and cause problems.
Brick or Concrete block posts should be core filled with concrete and have reinforcing steel up the centre that ties in with reinforcing steel in a deep footing
Finishing Gate Posts
Galvanized Steel Gate posts can be powder coated to match the finished gate before being installed or if painting the gate this can be done once the post is installed.
Concrete block posts should be hard plastered before a gate is measured up because this adds 10mm to 15mm of material to the post, which can make a difference to measurements.