Recommended Post Types and Sizes for Automatic Gates and Fencing
It is important to use the correct size and type of post for Automatic Gates and fencing to get reliable operation of life life span.
For Pool fencing and slatted metal fencing to 1.8m high a 50mm Square Aluminium Post is all that is needed.
Timber fencing to 1.8m high treated hardwood posts 100mm x 75mm is recommended.
For swing and Bi-folding gates the size of the posts depends on the weight and width of the gate and whether it is braced or not.
... READ MORE about bracing posts.
Light weight gates are defined as those made from light weight aluminium tubing with verticals spaced 100mm or so apart or chain link gates that have a steel tubular frame and wire mesh, heavier gates are those with an aluminium frame and aluminium slats or pine palings with a gap 50mm or less between slats. A very heavy gate is one with a steel or aluminium frame with heavy hardwood fitted or made from cast iron or similar material.
Note: this page is a guide only based on our experience installing gates, it is not a structural engineers specification.
Posts for Swing Gates
For light weight swing gates up to 1m wide a 50mm square aluminium post with a 3mm wall thickness will do so long as it is braced. If not braced then a 65mm square galvanized steel posts with at least a 2.5mm wall thickness is needed.
For heavier swing gates up to 1m wide 65mm square aluminium posts with at least a 2.5mm wall thickness are needed if braced, if not braced 75mm square galvanized steel posts with at least a 3mm wall is needed.
For very heavy gates up to 1m wide 75mm square galvanized steel posts are needed if braced or 100mm square galvanized steel with 3mm wall thickness if not braced.
For light weight swing gates up to 4m wide, heavier swing gates up to 3.2m wide or very heavy swing gates up to 2m wide a 75mm square galvanized steel post is recommended with at least a 3mm wall thickness if braced or 125mm square galvanized steel with 3mm wall thickness if not braced.
For light weight swing gates up to 5m wide, heavier swing gates up to 4m wide or very heavy swing gates with hardwood up to 2m wide a 100mm square galvanized steel post is recommended with at least a 3mm wall thickness if braced or 125mm square galvanized steel with 4.8mm wall thickness if not braced.
For gates larger than this it would need to be specified by a structural engineer.
Posts for Bi-folding Gates
For light weight Bi-folding gates up to 4m wide, heavier Bi-folding gates up to 3.2m wide or very heavy swing gates to 2m wide a 65mm square galvanized steel post is recommended with at least a 2.5mm wall thickness if braced or 100mm square galvanized steel with 3mm wall thickness if not braced.
For light weight Bi-folding gates up to 5m wide, heavier Bi-folding gates up to 4m wide or very heavy Bi-folding gates with up to 2m wide a 100mm square galvanized steel post is recommended with at least a 3mm wall thickness if braced or 125mm square galvanized steel with 4.8mm wall thickness if not braced.
Guide Posts for Sliding Gates
The size of these depends on the height of the guide post, slope across the driveway and weight of the gate.
For light weight and heavier sliding gates with a guide post less than 1.5m then a 75mm square aluminium single post with a 3mm wall thickness is all that is needed.
For very heavy gates or there's a steep slope across the driveway so a nylon guide block and rail is being used and the guide post is less than 1.5m then a single 100mm Aluminium post with 3mm wall thickness is all that is needed.
For all weights of sliding gates on a level driveway with a guide post between 1.5m to 2.2m a 100mm square galvanised steel guide posts with a 3mm wall thickness will do.
For all weights of sliding gates with a steep slope across the driveway and a guide post between 1.5m and 2.2m high a 75mm aluminium post with connection to a block wall in front of the gate or 2 x 100mm square galvanized steel posts one wither side of the gate and connected at the top are needed. For a free standing single posts a 125mm square galvanized steel posts with 4.8mm wall thickness is needed.
Guide posts over 1.5m high with a nylon block and rail particularly when there is a slope across the driveway can shudder when the gate moves
Installing Gate Posts
It is important that posts for swing gates are set firmly in the ground so the gate doesn't drop and drag on a driveway because if its automatic this will stop the automatic operator from working. An automatic operator cannot move a gate that is dragging on the ground, it doesn't know that the gate must be lifted to move it like a person would do.
... READ MORE about installing posts
If you have existing posts in good condition but they are bending a little with the weight of the gate, the posts could be braced rather than replaced saving money, time and effort