GFRC Primer: Why GFRC? Where/When to Use It? How Does It Install?
Glass Fiber Reinforced Concrete commonly called GFRC is light weight concrete that simulates either cast stone or architectural precast. The product can be designed to visually look the same as other cementitious products. The product is easily colored to match the color palette of the project.
- Much lighter – at least 50% less weight compared to other masonry products
- High strength to weight ratio – cost effective for higher elevation applications
- Much less expensive to install
- Less building structure needed
- Less erection equipment and yard management
- Much more durable compared to other exterior products such as stucco or EIFS
- With AAS technology and manufacturing process, GFRC can be combined with other materials such as cast stone, architectural precast or natural limestone for seamless design effects. Ability to create any custom color and finish required for the design.
- Manufacturing and customization at one of the AAS plants, as opposed to building the product at construction site that some other products require.
- Customize panel shapes and installation support based on architectural design and structural needs.
- Pre-engineered, built-in connections simplify installation, open up design options.
Where/When Do Use GFRC?
The product is about 50% of the weight of traditional cement based products and light weight is the primary driver for its use.
GFRC is often used:
- On structures where the core building structure cannot carry the weight of other cement based products.
- At or near the top of a structure where structural support may be insufficient for cast stone or precast.
- Where the design of a given piece (column capital, etc.) is complex and larger pieces ease installation.
- Where installation costs are an important consideration.
- Where skilled craftsmen are in short supply.
- On renovation and restoration projects.
- Where rigging and installation equipment is restricted.
- Interior applications, breezeways and transitional areas between indoor and outdoor spaces.
Product Life Cycle
The GFRC product has a Standard Architectural Specification under 03490. The specification requires a product that will perform structurally and comparably to other masonry products. As with all masonry products absorption, tensile strength, wind shear, and hardness (PSI) are all covered by its specification to provide product performance comparable to the longevity of masonry products in general.
Architectural Detailing for GFRC
Architectural detailing needs to be a shared responsibility between the architect, the manufacturer and the manufacturers engineer. An attachment design by the manufacturer, rather than the architect, is often appropriate for many GFRC projects. The shop drawings will provide the architect and installer an opportunity to review the attachment and make the final detailing.
General Rules for attachment:
- GFRC pieces up to about 4 feet x 6 feet can often be produced without an additional structural back-up. The manufacturer will add a stiffener-rib to the product back side for added support. A stiffener usually runs the height of the piece every 24 to 30 inches of the product and has very concentrated glass fiber to cement mix. The product can be attached via a veneer tie and strap, kerf and clip, or similar attachment to the structure of the building.
- Larger pieces or pieces where a stiffener-rib is not appropriate are generally hung with a metal stud back-up. The metal stud system is designed and attached to GFRC piece by the manufacturer as part of the cost of the GFRC on the project. Metal stud back-up is very similar to metal stud framing on most commercial projects, but designed with more precision. The metal stud back-up is usually attached with a grade #2 bolt to the structure of the building. There are occasions where the metal stud framing is welded to the structure. Again the specifications on the welding should follow AWS standards.
- Very large pieces (larger than 8 feet x 20 feet) will have tube steel back-up. The process is much the same as with metal studs discussed above. This back-up will be engineered by the manufacturer.
- Generally this is the decision of the general contractor since installation is not provided by the manufacturer. However, less costly installers are often used in the installation process rather than masons and other artisans. Installation can progress much faster than other masonry products and less expensive equipment at the job site.
- An excellent product to call-out jointing using caulk for a longer lasting and more moisture proof barrier.