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Historic Preservation - Technical Procedures

Spectitle:

Reattaching Loose Or Spalled Granite

Procedure code:

0446511R

Source:

Hsr - Departmental Auditorium Bldg/Wash, Dc - Grier, Brown..

Division:

Masonry

Section:

Granite

Last Modified:

06/14/2012

Details:

Reattaching Loose Or Spalled Granite



REATTACHING LOOSE OR SPALLED GRANITE


PART 1---GENERAL

1.01 SUMMARY

    A.  This procedure includes guidance on reattaching loose or
         spalled granite that is reusable and has not been
         extensively damaged.  This procedure may not be feasible
         for thin, friable pieces resulting from exfoliation.
         GENERALLY, THIS PROCEDURE SHOULD BE PERFORMED BY AN
         EXPERIENCED CONTRACTOR.

    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).

1.02 REFERENCES

    A.  American Society for Testing and Materials (ASTM), 
         www.astm.org
         

PART 2---PRODUCTS

2.01 MATERIALS

    A.   Two part polyester resin adhesive colored to match
         existing granite:  15-30 minute cure at 70 degrees F.;
         can be applied at temperatures as low as 40 degrees F.

    B.   Permanent coloring agent as required, compatible with
         adhesive, and as recommended by adhesive manufacturer.

    C.   Stainless steel rods for reinforcement:  1/4 inch
         diameter threaded rods, length as required.

2.02 EQUIPMENT

    A.   Stiff bristle brushes (natural fiber or nylon)

    B.   Polyethylene plastic mixing vessel for mixing adhesives
         and patching mortar


PART 3---EXECUTION

3.01 ERECTION, INSTALLATION, APPLICATION

    A.   Carefully remove all loose fragments of stone.  Set aside
         all pieces in good condition for reuse.

    B.   Clean exposed metal anchors.  Remove corrosion by
         scraping with a stiff wire bristle brush.

    C.   Remove unsound metal anchors and replace with new
         stainless steel anchors of similar size and shape.  Bed
         anchors in epoxy grout.

    D.   Remove dust and debris from building stone and fragments
         using a stiff bristle brush.

    E.   For small fragments (.5 cubic feet or less):

         1.   Coat exposed building stone sub-surface with
              adhesive.  Be sure to cover the entire surface,
              filling all voids.  Colored adhesive mix should be
              pre-tested to determine color match after drying.

         2.   While adhesive is still tacky, set stone fragment
              in place.  Prevent fragment from moving until
              adhesive is fully cured.

         3.   Clean any residual adhesive from the stone surface
              using water and stiff bristle brush.  Wet stone and
              fill any chips with patching mortar.  Tool surface
              level with surrounding stone.

    F.   For large fragments (more than 6 inches by 6 inches by 6
         inches):

         1.   Follow procedures in E. above.

         2.   After adhesive has cured, anchor fragments with 1/4
              inch smooth stainless steel rods.

              a.   Drill 1/4 inch holes at a 45 degree downward
                   angle through the face of the newly set stone
                   fragment.  Drill holes should extend at least
                   2 inches into the backing stone, 2 inches into
                   the fragment and should allow for the rod to
                   be countersunk at least 3/4 inches from the
                   face of the stone.

              b.   Space the anchor rods between 3 and 5 inches
                   apart and no less than 2 inches from any edge.

         3.   Clean any residual adhesive from the stone surface
              using water and a stiff bristle brush.  Wet stone
              and fill holes from countersunk rods with patching
              mortar.  Tool surface level with surrounding stone.

                         END OF SECTION
 


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