Fibre Glass Roof Coverings


GRP stands for glass reinforced plastic, aka fibreglass and is a product used extensively since the 1950’s on boats, model aircraft, water tanks, wind turbine blades and a whole host off other areas.

Fibreglass is both strong and lightweight, it is long lived and looks visually appealing.

Unlike other roof coverings such as SBS bitumen rolls, heat is not required to lay fibreglass so there is a reduced fire risk, this makes it a very suitable product for installations at hospitals, schools and other places where there are strict health and safety regulations. The installation of fibreglass does involve some specialist tools such as rollers but a small project could be completed by a competent DIYer.

Materials Needed for Roof Covering

Fibreglass roofingHere is a list of the materials you will need:

  • Replacement decking boards, never use old damp boards.
  • Resin: allow 1.5Kg/m2 for 450g glass or 2 Kg/m2 for 600g.
  • Top coat.
  • Acetone for the resin.
  • Catalyst (the rapid hardener).
  • Trims for the edges and up-stands.
  • Rollers.


The existing decking boards should be removed and replaced with sterling type boards. The drip and up-stand trims as well as any pre formed corner sections are then installed. Any joints in the decking boards must be bandaged to prevent cracks from appearing as a result of thermal movement.

Next the decking must be laminated and “wetted out” before a top coat is then applied.

Here are the advantages of the fibreglass system

  • Very tough and lightweight
  • Long lasting – in excess of 30 years if applied correctly
  • looks appealing and requires no heat source

Common issues

Below is a list of common problems along with solutions:

  • Watery white colour in resin – Most likely contaminated with water
  • Flaky topcoat – Either it was applied to thickly or was laid onto a wet laminate
  • De-lamination of decking – moisture penetration into the timber
  • Not curing – Lack of catalyst or temperature too cold
  • Patchy finish – Lack of catalyst or not mixed thoroughly