Handrail and guardrail are different components

A handrail guides and supports, giving a hand something to hold while walking or climbing. It usually sits 900 to 1000 millimetres high, with a section that fits the grip, typically 30 to 50 millimetres across or an equivalent.

A guardrail prevents falls. It normally has a top rail, an intermediate rail and a toe board, at about 1000 to 1100 millimetres, and it must take the horizontal force of a body striking it, which is a different design logic from a handrail.

The two can be combined into one system, with the top rail serving as the handrail and the intermediate rail and posts providing the protection. When they are combined, the stricter height and load requirement governs.

Mixing the terms is the commonest purchasing error. An inquiry that says guardrail may be quoted as a top rail alone, and one that says handrail may arrive without an intermediate rail. Name and function have to line up.

For the full range of components and fittings, see FRP guardrail and handrail products

Setting stanchion spacing

Common spacing runs from 1.2 to 1.8 metres, and the choice depends on three things: the horizontal load, the post section and the base detail.

Wider spacing puts more bending moment into each post and raises the demand on the base plate and anchors. Concrete substrates allow wider spacing; on a steel beam the local strength of the flange under a bracket has to be checked.

Tighten the spacing at corners, ends, platform openings and the first step of a stair. Those are the points where load concentrates and where people most often lose balance.

Manufacturer tables usually give a maximum spacing for a uniform horizontal load and another for a top point load. Design to whichever is stricter, instead of relying on a rule of thumb such as one and a half metres.

Load requirements

A handrail mainly takes a concentrated force, vertical and horizontal, usually of the order of 0.9 kilonewtons, with small differences between codes. That force acts anywhere along the rail, so the check uses the worst position.

A guardrail is more complex: a concentrated horizontal force at the top, a uniform load along the rails, and possibly impact. Industrial platforms also see accidental knocks from equipment being moved or serviced.

The combination usually applies horizontal and vertical force together. Checking one direction alone underestimates the moment at the base of the post.

FRP is brittle, so the safety factor follows the material rather than steel practice. Top deflection also needs a limit; the value comes from the project code, and FRP systems usually need a tighter one than steel.

Base plates and connections

Four base details are common: a base plate with anchors, a socketed base, a side-mounted bracket and a cast-in insert. The base plate is the most common and the most dependent on substrate strength and anchor quality.

When the post sits on grating, the grating cannot be the load path. Grating is designed for people and materials, not for the bending moment a guardrail delivers, so the base must be fixed to a beam or to independent structure.

A pad under the base plate spreads the pressure. FRP has far lower bearing strength than steel, and a small plate with high bolt torque crushes the grating or the plate itself.

Use stainless fasteners with an insulating washer against the FRP to avoid galvanic corrosion and stress concentration. Tighten to the maker's torque; too much cracks the plate or pulls the anchor out.

For fastener selection in detail, see fixings for FRP grating

Joints and continuity

System stiffness lives in the joints. Where rails meet posts and posts meet posts through a pin alone, repeated horizontal load works the connection loose and the whole guardrail starts to sway.

A joint should transmit moment, or the design should state that it is a pin. The two cannot be mixed: a rigid design with pin fittings is too flexible, and a pin design that is expected not to move is unrealistic.

Long runs should be split into sections joined by expansion joints, with the splits aligned to the building's movement joints so the guardrail does not restrain the structure.

Bolts and pins at joints need a locking device. Under vibration an ordinary nut backs off within weeks, so a spring washer or a lock nut is essential.

Thermal movement

FRP expands about ten to twenty microstrain per kelvin along the fibre and more across it. That is close to steel in order of magnitude, and on long runs the movement cannot be ignored.

A ten metre guardrail over a forty kelvin swing can change length by several millimetres, up to more than ten. Fixed hard at both ends, that movement becomes internal force acting on the base and the joints.

The right detail fixes one end and lets the other slide, with an expansion joint between. Use slotted holes or a sliding pad at the free end so the section can move while staying restrained horizontally.

Corners, bends and connections to the building restrain movement and need separate thought. Making those points the fixed ones and leaving the rest free is the more reliable arrangement.

Inspection and common failures

A loose base is the most common failure, showing as a post that rocks and a gap between plate and substrate. Push the top rail by hand and watch the base.

Cracks at bolt holes usually radiate outwards, caused by too little edge distance or too much torque. Replace the post when a crack appears; adding a washer is not a repair.

A sagging rail points to a long span or a thin wall, or to joints that have loosened and reduced the stiffness of the run. Check the joints before blaming the profile.

Chalking and exposed fibre are signs of UV ageing, usually on the south-facing or continuously exposed side. Inspect visually each quarter and re-torque the fasteners once a year.

Working with platforms and stairs

On a stair the handrail height is measured continuously along the nosing line, not vertically from the slope, or it ends up too high in places and too low in others.

The ends of a stair handrail should be closed off so they cannot catch clothing. A return bend or an end cap is the usual detail.

Platform openings, ladder access and lifting holes need a self-closing gate, a chain or a removable rail. These are the places where a guardrail is taken out and not put back, and they are a common cause of falls.

A toe board is usually 100 millimetres high and stops tools and material going over the edge. Leave a drainage gap between board and grating, or water will stand.

For how stairs and platforms come together, see stair and tread solutions

Inquiry and specification wording

State the system type, whether handrail, guardrail or a combined system, and add height, stanchion spacing, load class, base detail, colour and surface finish.

State the substrate as well: concrete, steel beam or FRP structure. The substrate changes the anchorage and the base detail completely, and the price moves with it.

List the accessories separately: bends, tees, expansion joints, toe board, end caps, fasteners and insulating washers. Missing accessories are the main source of later variations.

Say whether a third-party calculation is required, whether site training is needed, and how the goods are packed and shipped.

For base and rail dimensions, compare the FRP grating specification guide

• Decide first whether it is a handrail, a guardrail or a combined system.
• Work stanchion spacing back from load and base detail.
• The base must pass load into a beam or structure.
• Fix one end of a long run and let the other slide.
• Tighten spacing at corners and ends.