Spigot Balustrade Guide: Spacing, Glass Thickness and Height

A spigot balustrade, also called a point-fixed or frameless spigot-mounted glass balustrade, holds each glass panel on two short stainless steel posts and nothing else. Because the whole panel load passes through those two small footprints, the specification is less forgiving than a channel system: the spigot centres, the glass thickness, the barrier height and the fixing into the floor all have to agree with each other. This guide covers those numbers. For what a spigot is, how it is made and the profiles we manufacture, start with the glass spigot railing guide.

One caution before the tables. The figures below are the ones commonly cited in the glass trade and they are a sound starting point for a quotation. They are not a structural design. The design load for a balcony, a stair or a pool edge is set by the building code where the balustrade is installed, and the glass and spigot combination is confirmed against that by the project engineer. Our height and load requirements by country guide lists the usual starting points.

Spigots per panel and spigot centres

Two spigots per panel is the normal arrangement for panels up to about 1,200 mm wide. The spigots are typically placed at 800 to 1,000 mm centres, with each spigot set in 150 to 250 mm from the vertical edge of the panel. Setting a spigot too close to the edge concentrates stress at the corner of the glass; setting the two too close together lets the panel rock about them under a push at the top. Panels wider than about 1,200 mm are usually given a third spigot rather than wider centres.

Because the panel is fixed only at the bottom, the spigots also set the line of the whole run. A run of six panels is twelve spigots that must sit on one straight line and one level, and every millimetre of error at the floor shows as a visible step at the top edge a metre above. Lay the centres out against a string line before any core drilling, and read our guide to railing setting out and tolerances if the slab is anything but flat.

Typical panel widths and gaps

• Width. 900 to 1,200 mm is the usual panel for a spigot balustrade. Wider panels are heavier to handle, harder to keep plumb on two points, and more expensive to replace if one breaks.
• Gap between panels. 10 to 20 mm is typical. Many codes limit the opening so a 100 mm (or in Australia a 125 mm) sphere cannot pass, and a frameless run has no post to close the gap, so the panel gap itself has to comply. The gap also has to allow for thermal movement on a long run in the sun, which is covered in our note on thermal movement in glass railings.
• Height above floor. The finished barrier height is measured to the top edge of the glass, or to the handrail if one is fitted. The spigot grips roughly the bottom 100 mm of the panel, so a 1,000 mm barrier normally means a panel cut around 1,100 mm tall. Confirm the grip depth of the spigot you are ordering before cutting glass.

Glass thickness against barrier height

This is the decision that matters most on a spigot system. A channel supports the glass along its whole bottom edge; a spigot supports it at two points, so the glass itself does more of the structural work. The commonly cited pairings are below.

Commonly cited trade figures, not a design. Loads for public and commercial balustrades are higher and move the glass up a step. Confirm with the project engineer against the local code.

The handrail changes the answer because an interlinking rail ties the panels together, so if one panel breaks the rail still spans the gap and the neighbours share the load. Several codes, including BS 6180 in the UK and AS 1288 in Australia, are explicit that a frameless balustrade either carries a handrail or uses laminated glass that stays in place when broken. Which route a project takes is a design and cost decision; the glass-thickness side of it is set out in the glass railing thickness guide and the laminated make-ups in the laminated glass thickness chart.

Fixing the spigot into the floor

There are two ways to fix a spigot, and the floor usually decides. The choice between them is explained in the spigot guide; the specification points are these.

• Core-drilled. The pocket is typically 50 to 60 mm in diameter and 100 to 130 mm deep for a standard spigot, filled with non-shrink grout or a structural resin, and the spigot must not be loaded until the grout has reached strength, which for cementitious grout is days, not hours. The slab needs enough depth below the pocket to hold, and enough edge distance so the pocket does not burst the slab edge. On a balcony the pocket also has to be sealed so it does not become a path for water into the slab.
• Base-plate. The flange is bolted down with expansion anchors or resin anchors, usually four per spigot. Anchor edge distance is the usual problem: a balcony edge is exactly where the spigot wants to go and exactly where an expansion anchor is likely to spall the concrete. Resin anchors tolerate a smaller edge distance. The railing anchors and fixings guide covers the anchor choice for concrete, steel and timber.

A spigot on a waterproofed terrace is almost always base-plate fixed, and the base plate is bedded on a sealant that stays flexible. Cutting a core pocket through a membrane is a leak waiting to happen.

Glass edge work

A spigot balustrade needs no holes in the glass, which is one of its real advantages over a standoff or patch-fitted system: there is no drilled hole to start a crack from and the glass is cheaper to process. What it does need is a clean, flat-polished bottom edge, because the spigot jaws clamp through gaskets against that edge, and a chipped or out-of-square edge seats unevenly and loads one corner. All glass is cut, polished and then toughened; nothing can be adjusted on site afterwards, which is why our note on cutting and drilling toughened glass matters here more than on any other system. Measure after the spigots are set, not before.

Installation sequence

1. Set out the spigot centres on a string line and check the edge distances to the slab edge.
2. Core drill or drill for anchors, clean the holes, and fix the spigots plumb using a straight edge across the run.
3. Allow grout or resin to cure fully. Only then measure panel widths and heights from the fixed spigots and order the glass.
4. Fit the panels with the correct gaskets for the glass thickness, tighten the clamping screws evenly in sequence and check each panel for plumb and line.
5. Fit the interlinking handrail if the design has one, then torque-check every spigot before handover.

Common mistakes

• Ordering glass from the drawing instead of from the fixed spigots. Core pockets wander by a few millimetres, and toughened glass cannot be trimmed.
• SS 304 by a pool or on the coast. Spigots sit in the wettest, saltiest spot on the building. SS 316 is the grade for pools and sea air, as set out in the pool fencing railing guide.
• Wrong gaskets. A 12 mm gasket in a spigot holding 10 mm glass will tighten, then loosen. The gasket set must match the glass.
• No handrail and ordinary toughened glass. A free-standing 12 mm toughened panel at 1 m is common in the Indian trade and is accepted by some authorities, but it is the one combination several overseas codes rule out. If the balustrade is for export, check first; our pages for Australia and the UK explain what those markets expect.
• Spigots as the only thing holding a long run. A long terrace in direct sun needs its panel gaps sized for thermal movement, or the panels close up and load each other.

What to send for a quotation

The barrier height, whether a handrail will be fitted, the glass thickness you intend to use, whether the floor is new (core-drilled) or finished (base-plate), the location (pool, coastal, inland) and the total run length. From that we can confirm the spigot profile, the grade and the gasket set, and the quantities. The stainless steel spigots and aluminium-core spigots we manufacture are on the SS spigot category page.