The job of a roof-light sheet
Translucent FRP roof-light sheets bring daylight into factories, warehouses, sheds, greenhouses and canopies. They are made profiled to match the metal roofing around them or flat, on continuous sheet lines or by hand, from clear resin and glass reinforcement.
Their value lies in staying translucent. A sheet that yellows or loses its surface in the sun lets through less light each year and eventually shows exposed glass fibre.
Exposure questions to answer
Before choosing a grade
- Will the sheet face direct sun, and for how many hours a day?
- What climate: coastal, desert, industrial or temperate?
- Is there a surfacing film, gelcoat or veil on the weather face?
- Does the buyer of the sheet specify light transmission, colour change or a test method?
- Is the sheet clear or tinted?
Where each sheet grade fits
The catalogue’s SPR 201 sheet group is organised by exposure. SPR 201 RL (UV) is the clear, UV-stabilised roof-light grade for sheets exposed to sunlight and for industrial daylighting. SPR 201 RL is the standard roof-light grade. Coloured sheet uses the yellow sheet grades, including the UV-stabilised yellow.
The distinction is about the finished sheet’s life in the sun, not about processing: the grades are laminated and cured in the same way, with MEKP and cobalt octoate added separately.
Published typical values
| Property | UV-Stabilized Roof Light Resin (SPR 201 RL (UV)) | Roof Light Sheet Grade Resin (SPR 201 RL) | UV Stabilized Sheet Grade Yellow Resin |
|---|---|---|---|
| Appearance | Clear transparent liquid | Water White | Yellow, factory master yellow shade (pre-pigmented liquid) |
| Viscosity (typical) | 200–400 cPs | 280 cPs | 280 cPs at 25 °C |
| Gel time / pot life (typical) | 6.5–10 minutes | 6.5 Minutes | 6.5 minutes at 25 °C |
| Styrene content (typical) | 30–40% | 35% | 35% by weight |
| Source of values | 2026 catalogue; grade TDS | Roof Light Sheet Grade Resin TDS | UV Stabilized Sheet Grade Yellow Resin TDS |
Typical values, reproduced from each product’s own published data. They describe the liquid resin at its reference condition, not a finished part, and are not guaranteed limits.
What the resin cannot do alone
The resin is one factor in weathering. Glass content and how evenly it is wetted, the sheet thickness, the surfacing on the weather side, cure completeness and the climate all decide how a sheet ages. A well-stabilised resin in a poorly cured, resin-starved sheet will still weather badly.
No service life in years is published for any of these grades, and none should be inferred from accelerated laboratory hours. If the sheet’s customer names a performance requirement, test the finished sheet against it.
Trials before production
Run the grade on the production line at production speed and temperature, with the actual glass and surfacing. Check wet-out — a translucent sheet shows every dry strand and trapped air — along with cure and surface quality. Keep retained samples from the trial so that later weathering can be compared with a known starting point.