Pool Fence Vertical Rail Spacing Victoria: The 100mm Rule

Vertical rails on your pool fence must have no more than 100 mm between them. The rule is simple, the measurement is unambiguous, and the standard tool inspectors use is a 100 mm rigid spacing gauge. If the gauge fits between two rails at any point along the fence — your barrier fails. The companion rule — no climbable horizontal rails on the outside — is the single most common Form 23 failure on older inland Geelong properties.

What AS 1926.1-2012 Specifies

• Vertical rail gaps: maximum 100 mm clear distance between adjacent vertical rails
• Horizontal rails: must NOT be present on the outside (non-pool) face of the fence at heights between 100 mm and 1100 mm above ground (the climbable range)
• If horizontal rails are present on the outside: they must be spaced at least 900 mm apart vertically (so a child can’t use them as ladder rungs)
• Decorative elements: ornamental scrollwork, pickets, or features that create handholds within the climbable range fail the same test as horizontal rails

Why 100 mm

The 100 mm gap is set against child head and torso dimensions — under-5 head circumference and chest depth at the smallest end. Below 100 mm, a child cannot pass through the gap; above 100 mm, head entrapment risk emerges. The figure is consistent with international pool barrier standards.

Where Inspectors Find Spacing Failures

Decorative timber paling fences

Older Geelong properties sometimes have timber pickets used as pool fencing. Picket spacing on standard timber fencing is typically 50–80 mm — fine. But where pickets have warped, rotted, or been removed, gaps over 100 mm appear. We see this in 1980s–90s timber paling fences across Newtown, Belmont, Highton.

Aluminium tubular fence panels with bent rails

Modern aluminium pool fencing has rails at standard spacings — usually 96 mm. Pass at install. But if a rail has been hit and bent (BBQ, kids, mower), the gap can open up to 110+ mm at the bend. Inspectors check at every panel, so a single damaged section flags the whole barrier.

Glass pool fencing with damaged or missing panels

Frameless glass pool fencing relies on the panel itself as the barrier. A cracked panel, a missing panel, or a panel installed with a wider clamp gap creates the same failure mode.

Renovations that left odd gaps

Pool fence panels removed for landscaping access, then re-installed with slightly different post positions. Where one post-to-panel junction now has a 105 mm gap.

The Horizontal-Rail Problem (the One That Fails Older Geelong Fences)

Older steel-tube pool fencing often has visible horizontal rails on the outside face — typically one rail near the bottom (around 200 mm) and one near the top (around 1000 mm). Each rail acts as a ladder rung for a child climbing from outside. AS 1926.1-2012 fails the barrier on this alone, regardless of vertical-rail spacing.

This is the single most frequent first-inspection failure we see on Geelong properties built between 1975 and 1995 — well before the current standard tightened up. The fix options are:

• Replace the entire fence panels with vertical-only aluminium fencing — typically $90–$150 per linear metre installed
• Cap the horizontal rails with non-climbable covers — rarely passes inspection because the cap itself adds another foothold
• Reverse the panels — if the horizontal rails happen to be on the inside (pool-side) of the install (the original orientation got flipped during construction), reversing the panels can solve it. Only viable for some panel types and rarely cost-effective vs replacement

How Inspectors Measure Gaps

The standard inspection tool is a 100 mm rigid spacing gauge (essentially a hard plastic block sized 100 × 100 × 50 mm). The inspector pushes the gauge between every pair of adjacent vertical rails. If the gauge passes through, the gap fails.

For glass panels and unusual barrier types, the inspector measures with a tape measure at multiple points along the panel.

What’s NOT a Spacing Failure

To distinguish from common confusion:

• Gaps wider than 100 mm at corners or end-posts where two perpendicular fences meet — usually a different geometry that’s measured separately and rarely fails.
• The gap between the bottom of the fence and the ground — this is the under-fence gap rule (also 100 mm max), measured separately.
• Decorative top-rail gaps above 1200 mm — outside the inspectable range as long as overall height is met.