# 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.

## 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

| Property | Typical specification |
| --- | --- |
| Composition | Polyester resin with chopped glass fibre |
| Weight | Commonly 1,800 — 2,400 g/m² |
| Surface | Gel coat or surfacing film, UV protective |
| Light transmission | Stated as a percentage |
| Profile | Matched to the adjacent metal sheet |
| Fire class | Named 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**.

## Frequently asked questions

### How long does FRP sheet last on an Indian roof?

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.

### FRP or polycarbonate for roof lights?

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.

### Can FRP be walked on?

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.

## Sources

- [IS 875 (Part 3)](https://standards.bis.gov.in/website/published-standards/department-wise) — Wind loads — roof cladding
- [ECBC 2017](https://beeindia.gov.in/) — Building envelope — skylights
- [EN 13501-1](https://standards.cencenelec.eu/ords/f?p=CEN:105) — Reaction to fire classification

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Source: https://hagerstone.com/materials/frp-translucent-sheet