FRP Grating Installation Guide
FRP grating is straightforward to install — that is one of its selling points. But a few rules govern span direction, bearing width and clip spacing, and getting them wrong shows up later as rattle, edge deflection or panel creep. This guide is what our install briefing covers.
Before you start: check the supports
Three things to confirm against the layout drawing:
- Span direction. Molded grating carries load in both directions but must still bear on all four sides where the load table assumes it. Pultruded grating carries load along the bearing bars only — the bars must span the short way between supports.
- Actual clear span. Measure the clear distance between supports, not the drawing's nominal span. The load table applies to the clear span plus bearing.
- Support flatness and level. FRP follows the supports. Shims and leveling brackets are cheaper than living with a rocking panel.
Bearing and overhang rules
| Rule | Value | Why |
|---|---|---|
| Minimum bearing per panel edge | 25 mm (1 in) | Prevents edge crushing and panel walk-off |
| Recommended bearing | 40 mm | Spreads load; allows for support tolerance |
| Maximum unsupported overhang | 50 mm | Prevents edge deflection under foot traffic |
| Panel-to-panel gap | 3–6 mm | Thermal movement and tolerance absorption |
| Panel-to-wall gap | 10 mm min | Allows removal without tools |
Clip spacing — the part everyone underestimates
Clips stop panels lifting, rattling and creeping. The standard pattern:
- "C" clips (panel-to-panel): at each panel corner where four panels meet, and every 1 200 mm along shared edges
- "W" / edge clips (perimeter): every 600 mm on exposed outer edges
- "M" / hold-down clips (against supports): every 1 200 mm where the panel meets a wall or kerb
- Hardware: 316 stainless bolts with the molded clip; torque to snug — do not crush the bar
Walkway applications that skip clips “temporarily” are the main source of post-installation complaints: the first year of foot traffic works panels loose and the deck starts to drum.
Cutting on site
Molded grating may be cut anywhere without edge sealing — the corrosion barrier is the full section. Pultruded grating cut ends should be sealed with the supplied end-cap or a compatible resin coat, because the cut exposes the bar's longitudinal glass.
- Tools: circular saw with diamond or carbide blade for straight cuts; angle grinder for openings
- PPE: dust mask and eye protection are non-negotiable — see the cutting & machining article for dust control
- Cut from the gritted side down where possible to reduce surface chipping
Common site mistakes
- Installing pultruded panels with bearing bars parallel to the supports (zero strength that way)
- Over-spanning — supports set out to 1.2 m centres while the quoted table assumed 1.0 m
- Forgetting that a cut-out for a pipe removes bearing: add a trimmer bar or support under any opening over 150 mm
- Using galvanized hardware in chemical service — specify 316 stainless throughout