Railing Setting Out and Tolerances

Most of what makes a finished balustrade look right or wrong is decided before any hardware is fixed. Even gaps, a straight line and panels that land sensibly at the ends are a setting-out result, not a manufacturing one.

Survey the opening, not the drawing

Buildings are not built to the drawing. Walls run out of plumb, slabs dip, and openings are rarely square. Take the actual dimensions after the structure is up, at more than one height, and write down where the run is not square or level rather than averaging it away.

This matters more here than on most trades because toughened glass cannot be cut or adjusted after it is made.

Set out from the centre

Given a run that does not divide into whole panels, you can put the odd dimension in the middle or split it between the two ends. Splitting it to the ends looks deliberate; leaving one narrow panel in the middle of a run looks like a mistake, because it is visible against the rhythm of everything either side.

Where the run meets a wall, a newel or a change of direction, decide which element governs and set out away from it.

Design the gaps in

Clearances are not slop, they are what absorbs building tolerance and thermal movement. Panel-to-panel gaps should be consistent along the run; that consistency is what the eye reads, far more than the absolute dimension. Allow clearance where glass meets a wall or a post, and keep the gap under a point-fixed panel within whatever your local requirement permits — see gaps and child safety.

Movement matters on long external runs in particular; the reasoning is in our thermal movement guide.

What each system needs from the setting out

• Continuous channel — level is everything. The base shoe telegraphs any dip in the slab straight into the glass line, so pack and shim before fixing rather than after.
• Brackets — centres are set against panel size and design load, then each bracket is plumbed individually. Mark them all before drilling any.
• Spigots — the whole load goes through a few small footprints, so position accuracy and anchor edge distance both matter more. Core positions have to be planned before the floor finish is laid.
• Side mount — the slab edge itself is the datum, and its straightness becomes the railing's straightness.

A sensible sequence

1. Survey the opening and record where it is out.
2. Decide the panel split and set out from the centre.
3. Mark fixing positions and check them against anchor edge distance — see anchors and fixings.
4. Dry-lay or string the line and stand back and look at it before drilling.
5. Order glass to the surveyed sizes with cut-outs specified.
6. Fix the base true, then set glass, then wedge and lock.

Send us the surveyed dimensions and we will work the panel split and the cut list back to you — contact us.