U.S. General Services Administration
Technical Procedures Disclaimer
Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.
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We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.
This standard includes general information on an alternative material for use in the replacement of severely deteriorated terra cotta ornament. Micro-cotta is a lightweight, polymer-based composite concrete manufactured by Patentech Corporation of Sugar Grove, Illinois. It is a replacement alternative suitable for reproducing the appearance of terra cotta, cast stone, slate and cast iron. The characteristics of micro-cotta as a replacement for terra cotta are believed to be superior to more traditional replacement materials such as cast stone, fiberglass, and even replacement terra cotta. Some characteristics of micro-cotta include the following:
- Polymer-based micro-cotta utilizes a finer aggregate than cement-based concrete
- Capable of reproducing detail with sharp definition
- Greater resistance to weathering:
- Lower absorption rate (1% compared to 13% for concrete and 7% for terra cotta)
- Color value and tone of material is relatively stable during aging process unlike that of fiberglass laminates or cast stone
- Micro-cotta’s resistance to cracking and spalling compared to that of terra cotta is not conclusive.
- Micro-cotta is lightweight (70 lbs./cubic foot)
- It is 50-70% lighter than masonry products and, therefore, substantially less expensive to install. Micro-cotta is most commonly produced from a mold of the original unit. It is anchored using standard conventional masonry anchors (preferably stainless steel, as recommended by Patentech Corporation).