Epoxy Patching Cracks In Limestone

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.



  1.  This procedure includes guidance on patching cracks in limestone using an epoxy resin. This type of repair is suited for dormant (inactive) cracks no larger than 3/8" wide.
  2. 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.  Contractor: A skilled firm with not less than five (5) years experience in masonry repointing and restoration. The Contractor shall be required to submit references for five (5) successfully completed projects of similar nature.
  2. Source of Material: Obtain materials for stone restoration from a single source for each type of material required, to ensure match of quality, color, pattern, and texture.


  1.  Environmental Requirements: Perform work only in dry and otherwise favorable weather conditions. Protect repaired masonry against freezing or excessively rapid drying for at least 48 hours after being laid. Do not repoint mortar joints or repair masonry unless air temperatures are between 40 F (4 C) and 80 F (27 C) and will remain so for at least 48 hours after completion of work.



  1. Akemina www.akemina.com
  2. Euclid Chemical Company www.euclidchemical.com


  1. Epoxy-Based Stone Repair Adhesive: A commercially available, two component, moisture insensitive, high modulus, low viscosity, epoxy resin-formulated for penetrating deep into thin masonry cracks, such as "Akepox 1005 or 1006" (Akemina), "Eucopoxy Injection Resin" (Euclid Chemical Company), or approved equal.
  2. Single Source Responsibility: Provide epoxy resin, hardener and solvent produced by the same manufacturer.
  3. Acetone (C3H6O):
    1.  A volatile fragrant flammable liquid ketone used chiefly as a solvent and in organic synthesis.
    2.  Other chemical or common names include Dimethyl ketone; Propanone
    4. Available from chemical supply house or hardware store.
  4. Limestone Dust
  5.  Clean, potable water


  1. Syringe
  2. Stiff bristle brushes (non-metallic)



  1.  Protection:
    1.  Take whatever precautions are necessary to protect the existing building from damage resulting from work under this section.
    2.  Prevent mortar and patching compounds used in repointing and repair work from staining face of surrounding masonry and other surfaces. Remove immediately mortar and patching compounds in contact with exposed masonry and other surfaces.
    3.  Improper use of chemicals may constitute a health hazard. Refer to manufacturer's Material Safety Data Sheets for hazard data, special protection for use and precautions to be taken in handling and storage. Comply with manufacturer's recommendations for proper use of chemicals.


  1. Thoroughly clean dust, dirt and debris from crack.
  2.  Wipe surfaces to be bonded with acetone and allow to dry thoroughly.
  3. Thoroughly and completely mix resin and hardener (2 minutes). Mix at low speeds to minimize entrapped air. Blend the epoxy adhesive to match color matrix of adjacent limestone by adding color limestone dust or pigment.
  4. Mask stone surfaces adjacent to crack to prevent staining of the limestone during repair operation.
  5.  After mixing, inject epoxy into cracks with a syringe and allow to seep in. Continue to apply material until crack is full. Sprinkle limestone dust on epoxy adhesive to mask crack.
  6. F. Clean tools and any tape residue with acetone or solvent specifically formulated for the particular product used.