What it is called, by market
One concept, four markets. Where a name means something else locally, the card says so rather than leaving you to find out on site.
United Kingdom
Same word, different thingspindle
also baluster, newel, handrail, string, balustrade
A STRING is the raking board into which the treads are housed. BALUSTRADE is the whole assembly, and a SPINDLE and a BALUSTER are the same component with the first used more in domestic joinery.
Australia
Close, not identicalbaluster
also spindle, newel post, stringer, balustrade
Stringer used where British usage says string, with balustrade for the assembly as in the UK.
United Statesyours
Same word, different thingbaluster
also spindle, newel post, stringer, guard, railing
GUARD is the code term for the whole barrier and is what a code clause will say; STRINGER is the raking board. Railing covers both the handrail and the whole assembly depending on context.
Canada
Same word, different thingbaluster
also spindle, guard, stringer, picket
As the United States, and STRINGER collides with Canadian strapping usage, where stringers can also mean light battens run across framing.
The governing standard, by market
United Kingdom
Approved Document K / BS 6180
Protection from falling, including guarding heights and the 100 mm sphere rule, and barriers in and about buildings.
United States
IRC R312 / IBC 1015
Guards: required height, the 4-inch sphere limitation, and the loads a guard must resist.
Calculators for this
Each works in either measurement system, and the terminology on the page follows whichever market you have selected.
Frequently asked questions
- Why is the spacing rule expressed as a sphere rather than a gap?
- Because the hazard is a child's body passing through, and a child is not a flat gauge. Both markets express the limit the same way — a sphere of 100 mm in British guidance, 4 inches in American — and the sphere must not be able to pass through any opening in the guarding. Stating it as a sphere rather than a dimension catches the openings a simple width measurement misses: a triangular gap at the bottom of a flight where the tread, the riser and the bottom rail meet; a diagonal opening in a chevron pattern; the gap beside a newel where the rake changes. It is also why the rule is checked at the worst point rather than at the typical spacing, and why a balustrade that measures correctly between spindles can still fail where the geometry changes.
- How many spindles does a flight actually take?
- More than the run divided by the spacing, and the arithmetic has two traps. The first is the same plus-one that catches every spacing calculation: a run with n gaps has n+1 verticals, and forgetting it leaves the flight one short at the top. The second is the rake. On a raking flight the spindles stand vertical while the rail climbs, so the horizontal spacing between them must be measured along the horizontal, not along the rail — spacing set out along the raking rail produces horizontal gaps larger than intended and can fail the sphere test even though the rail spacing looks right. On a stair with two spindles per tread the count comes from the tread number instead, which is why most joinery schedules give spindles per tread rather than a spacing.
- What is the string, and why does its type change the whole stair?
- It is the raking board each side that carries the treads, and there are two kinds that look different and are built completely differently. A CLOSED or housed string runs as a continuous board with the treads and risers housed into trenches cut in its inner face, wedged and glued — so the ends of the treads are hidden and the stair reads as a solid diagonal. A CUT or open string is cut to the profile of the steps, so the tread ends are exposed and finished with a return nosing, and the balusters sit on the treads rather than on the string. The second is more work, more visible, and is the traditional arrangement on a stair meant to be seen. Which one is being priced changes the joinery substantially, and a drawing that only shows a rake has not said.