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Patching Holes in Granite

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.


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 patching holes in granite using a mortar patch and bonding agent. This procedure is appropriate for use on holes measuring less than 3 cubic inches. For cementitious patch repair, see also 04465-28-R.

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).



A. Sika Corporation


A. Repair mortar is to match the original mortar mix. Laboratory test results will serve as standard for mix proportions and color.

B. Adhesive for bonding fresh mortar to hardened material, such as "Sikadur Hi-Mod Adhesive" (Sika Corporation), or approved equal.

C. Clean, soft cloths

D. Clean, potable water


A. Stiff natural-bristle brush

B. Chisel

C. Rubber mallet

D. Trowel

2.04 MIXES

A. Measure materials by volume or equivalent weight. B. Do not measure by shovel. Use known measure.

C. Mix ingredients in clean mechanical batcher for 3-5 minutes.

D. Let mortar sit for 20 minutes prior to use, to allow for initial shrinkage. Use mortar within 1=AB hours of initial mixing.



A. Remove previous mortar patches. Clean all stone areas and wall surfaces to be repaired of all debris, dust, oil, dirt and grime by brushing with a stiff, natural-bristle brush.

B. Carefully cut back damaged granite using a chisel and mallet. Locate cuts in the existing granite to enable the least conspicuous patch and give the straightest, most uniform and smallest joint possible. Remove dust and debris with a stiff, natural bristle brush.

C. Brush coat the stone surface with adhesive following manufacturer's instructions.

D. Place patching mortar in layers no thicker than 3/4". Roughen surface of each layer to provide key for the next.

E. Keep each layer damp (80 -90 RH) for 72 hours or until mortar is set. In patches which are deep enough to require more than one application, coat each layer with adhesive prior to placing next layer.

F. Separation at the edges of the patch and hairline cracking will be unacceptable.Those patches found will be removed and refilled as directed by the Contracting Officer.