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Historic Preservation - Technical Procedures

Spectitle:

Removing Exfoliated Granite

Procedure code:

0446515R

Source:

National Capitol Region Specifications

Division:

Masonry

Section:

Granite

Last Modified:

02/24/2012

Details:

Removing Exfoliated Granite



REMOVING EXFOLIATED GRANITE


PART 1---GENERAL

1.01 SUMMARY

    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:

         1.   Safety Precautions

         2.   Historic Structures Precautions

         3.   Submittals

         4.   Quality Assurance

         5.   Delivery, Storage and Handling

         6.   Project/Site Conditions

         7.   Sequencing and Scheduling

         8.   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

    A.   Qualifications:

         1.   Contractor performing the work shall have a minimum
              of 5 years experience in masonry restoration work
              of the type described for this project.

         2.   If requested 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:

         1.   Secretary of the Interior's "Standards for
              Rehabilitation".

         2.   Preservation Brief No. 1, "The Cleaning and
              Waterproofing of Historic Masonry Buildings".

    C.   Test Panels:  Each alternative method for each type of
         cleaning.


PART 2---PRODUCTS

2.01 MATERIALS

    A.   Clean, potable water
         
    B.   Weathered or dry-grit blasted flat block of granite or
         carborundum brick

2.02 EQUIPMENT

    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


PART 3---EXECUTION

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.

                         END OF SECTION