Short answer: measure the opening at top, middle and bottom and use the smallest reading. Deduct hinge and latch clearance, get the diagonal brace running the right way, and pick your section size based on how wide and how heavy the gate is going to be.
Step 1 — Measure the opening at three points
Hook your tape between the two posts and take a reading at the top, the middle and the bottom of the opening. Fence and gate posts are almost never perfectly parallel, especially on a slope. Whatever the smallest of those three numbers is — that's your working opening. Build to the biggest one and the gate will jam at the tightest point.
Step 2 — Deduct your clearances
On the hinge side, take off 10–15mm for the hinge knuckles to sit in. On the latch side, take off another 5–10mm for the latch hardware and a small visual gap. For a double gate, deduct those clearances at each post, then take another 5mm out of the middle for the centre gap.
Step 3 — Get the diagonal brace right
The single biggest mistake on DIY gates is running the diagonal the wrong way. The brace must run from the bottom hinge corner up to the top latch corner. That puts the brace in compression — it pushes against the latch corner and stops the gate sagging on the latch side a few months in. Run it the other way and the brace is in tension, the welds eventually pull, and the gate droops.
Step 4 — Pick the section size
- 40×40 SHS — small pedestrian gates, light garden gates, up to about 900mm wide.
- 50×50 SHS — typical side gates and pool gates, 900mm–1.5m wide.
- 65×65 SHS — heavy single gates, double drive gates, anything carrying solid cladding or sheet steel.
If your gate carries weight (timber pickets, sheet steel, mesh infill), step up one section size. Same goes for anything over 1.8m wide.
Finish and hardware
DuraGal or hot-dip galvanised is the right call for any outdoor gate on the Gold Coast — painted black gates rust at the welds within a couple of wet seasons. Heavy-duty barrel hinges welded to the post and to the gate frame will outlast bolt-on hardware ten times over.
Send us your measurements and we'll fabricate the frame ready to hang.
We stock SHS in all common gate sizes and fabricate frames as part of our fabrication service.
