An understanding of basic molding and casting constraints of glass fiber reinforced concrete as well as standard tolerances for GRC will provide a better understanding for the architect and engineer of how GRC design shapes and forms are to be manufactured. Here are some design considerations that may affect the cost of GRC used in your project:
The amount of detail: GRC can reproduce intricate details or smooth sweeping curves. Details and undercuts require rubber mold liners. Simple smooth flats and curves can be cast in rigid molds of fiberglass. While rubber molds are slightly more expensive, the cost may be minimal if the casting is repeated several times.
Number of repetitive pieces of glass fiber reinforced concrete: Numerous casts of a GRC shape are more economical per piece, than onetime- only casts.
Size: GRC can be cast in pieces up to 8.5 meter in length. However, the longer the length, the more difficult it is to handle and ship the GRC casting. We recommend a maximum length of 3.6 meter for most moldings. If longer lengths are required, pieces can be field joined.
Surface Finish: GRC can be cast with a limestone or precast finish, such as sandblasting, acid etching or retarding or the GRC can be painted. The lowest priced finish is usually a plain smooth GRC.
Special Reinforcements: Some specific design considerations are corners, draft angles, reveals, and finishes. All GRC corners should have a radius of between 1.5 mm and 3 mm unless otherwise noted.
Draft Angles and Reveals: Draft angles are designed bevels which allow the mold to release the GRC parts and/or pieces. Reveals incorporated in a design should have draft angles present.