Removing Exfoliated Granite
- Procedure code:
- National Capitol Region Specifications
- Last Modified:
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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.
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.
A. This procedure includes guidance on removing exfoliation from granite surfaces.
NOTE: THE INTENT OF THIS PROCEDURE IS NOT TO REFINISH OR BRIGHTEN THE GRANITE; RATHER, IT IS TO REMOVE LOOSE MATERIAL THAT OTHERWISE WOULD RETAIN DIRT AND MOISTURE.
B. See 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections:
- Safety Precautions
- Historic Structures Precautions
- Quality Assurance
- Delivery, Storage and Handling
- Project/Site Conditions
- Sequencing and Scheduling
- General Protection (Surface and Surrounding)
These guidelines should be reviewed prior to performing this procedure and should be followed, when applicable, along with recommendations from the Regional Historic Preservation Officer (RHPO).
1.03 QUALITY ASSURANCE
- Contractor performing the work shall have a minimum of 5 years experience in masonry restoration work of the type described for this project.
- If equested by the Owner, furnish a statement of the experience and qualifications of the firm and of the key personnel who will work on this project. Include the names and addresses of successful projects completed, and for each, the name and address of the owner and the architect.
B. Reference Standards:
- Secretary of the Interior's "Standards for Rehabilitation".
- Preservation Brief No. 1, "The Cleaning and Waterproofing of Historic Masonry Buildings".
C. Test Panels: Each alternative method for each type of cleaning.
A. Clean, potable water
B. Weathered or dry-grit blasted flat block of granite or carborundum brick
A. Pressure water rinsing equipment (measuring between 100 and 400 psi for low-pressure; between 400 and 800 psi for medium pressure).
B. Fan-type spray tips (25 degree fan spray)
C. Stiff fiber-bristle brushes
3.01 ERECTION, INSTALLATION, APPLICATION
A. General rinsing of granite surface: Maximum 800 PSI, 5- 10 GPM, 25 fan angle, not less than 6" from surface, at an angle of 45 to 90 from wall surface. Take special care to protect all adjacent materials not intended for abrasive treatment, such as polished granite, wood or glass.
NOTE: IF WATER SOAKING AND PRESSURE RINSE SATISFACTORILY REMOVE FRIABLE SURFACE MATERIAL LOOSENED BY SALT CRYSTALLIZATION, THE FOLLOWING PROCEDURE MAY NOT BE NECESSARY.
B. Removal of exfoliated granite material: If required to remove all loose material, rub granite surface with a weathered or dry-grit blasted flat block of granite or carborundum brick.