TerraGlas Frequently Asked Questions

What is TerraGlas?
TerraGlas combines the best features of terra cotta and GFRC (Glass Fiber Reinforced Concrete). TerraGlas is a composite of terra cotta clays, glass fibers for tensile strength, mineral aggregates, polymers and Portland cements.
Why should I use TerraGlas to replace terra cotta on my historic building?
  • Better color match. Terra cotta is a difficult material to replace. Because most terra cotta clays are no longer available, an exact match in fired terra cotta is probably impossible.
  • Better detail match. Terra cotta clay shrinks. That means that if a mold is taken from a historical piece of terra cotta and then used to cast another piece of terra cotta, the new piece will shrink by up to 10% or more during drying and firing. A 24" piece may shrink to only 19" long, and leaving a 5" gap to fill. This means molds from existing pieces cannot be directly used for the replication of historic pieces. To make the pieces the same size, an oversized mold is required. This requires a "re sculpting" of the models, with all the risk, cost and variability that that involves.
  • Stronger material. TerraGlas provides a much higher impact strength than fired terra cotta. The pieces are reinforced with glass fibers embedded in a cementitious matrix. Less load on the historic structure. The weight of TerraGlas is typically less than half the weight of terra cotta. This puts less stress on the historic structure. Easier and faster installation. Because TerraGlas is both lighter and can have the anchors "cast in" the installation is faster, easier and more secure.
  • Better value. TerraGlas replacements for terra cotta are typically about half the cost of terra cotta. Couple that with labor savings and faster schedules, and the savings can be even more dramatic.
How do I match the new architectural TerraGlas to the historic architectural terra cotta?
Stromberg can analyze your terra cotta sample to determine the formulation of the terra cotta (the clay and the grog) and we also identify the glaze so that your restoration elements match the appearance of the originals.
Where can I find a reliable source of unbiased information on terra cotta restoration and preservation?
The National Park Service (NPS) has a Historic Preservation Service division. They have established the official standards for the preservation of historic structures: The Secretary of the Interior's Standards for the Treatment of Historic Buildings. The National Park Service also offers Preservation Briefs which are the professional standard for preservation and restoration in the United States.