FRP Translucent Sheet for Roof Lights and Cladding

FRP translucent sheet is glass fibre reinforced polyester sheet, profiled to match the surrounding metal roof sheet and widely used for industrial roof lights and wall lights. It is sold by weight per square metre, but its service life is set by the gel coat or surfacing film that protects it from UV.

By Dhruv Agarwal · · 1 min read

What it is

Glass fibre reinforced polyester sheet, profiled to match the surrounding metal roof sheet. Translucent, rigid, cheap, and widely used for industrial roof lights and wall lights across India.

Specification at a glance

PropertyTypical specification
CompositionPolyester resin with chopped glass fibre
WeightCommonly 1,800 — 2,400 g/m²
SurfaceGel coat or surfacing film, UV protective
Light transmissionStated as a percentage
ProfileMatched to the adjacent metal sheet
Fire classNamed EN 13501-1 class

The specification that decides service life

FRP is sold by weight per square metre, which sets stiffness and strength, but service life is set by the surface protection. Once UV has eroded the resin at the surface, the glass fibres stand proud, the sheet goes rough and opaque, and it embrittles.

So the order should state the surfacing system, not just the gram weight.

Where it belongs

Industrial and warehouse roof lights · wall lights in shed elevations · canopies and covered walkways where cost governs · temporary and short-life structures · buildings where the roof sees little handling and impact risk is low.

Where projects go wrong

  • Weight specified, protection not. The sheet then fails early and everyone blames FRP rather than the specification.
  • Fixings without oversized holes. FRP moves with temperature and cracks around pinned screws.
  • Sheet used as a walking surface. A genuine safety hazard.
  • End laps too short for the slope, siphoning water back.
  • Mixed profiles, so the FRP does not nest correctly with the metal sheet and the side lap never seals.

Standards referenced

Wind loading on roof cladding under IS 875 (Part 3). Skylight provisions under ECBC 2017. Reaction-to-fire classification to EN 13501-1.

Standards referenced

  • IS 875 (Part 3) — Wind loads — roof cladding (Bureau of Indian Standards)
  • ECBC 2017 — Building envelope — skylights (Bureau of Energy Efficiency)
  • EN 13501-1 — Reaction to fire classification (CEN-CENELEC)

Frequently asked

It depends almost entirely on the surface protection. A sheet with a proper gel coat or surfacing film resists UV for many years; an unprotected sheet yellows, the resin erodes and the glass fibres become exposed as a rough surface within a few seasons, after which light transmission drops sharply and the sheet becomes brittle. The protection layer, not the base laminate, is what should be specified and verified.

Polycarbonate has much higher impact resistance and holds clarity longer, so it is the better long-term choice and the safer one where anything could fall on the roof. FRP is cheaper, stiffer and easier to profile to match unusual metal sheets. On a budget-driven shed FRP is common and acceptable; on a long-life facility polycarbonate usually justifies the difference.

No. Neither FRP nor polycarbonate roof lights are a walking surface, and falls through roof lights are a recurring cause of serious injury on industrial roofs. Any maintenance access plan must route walkways around them, and where the risk cannot be designed out, load-bearing covers or safety mesh below the sheet should be provided.

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