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.
- This procedure includes guidance on re-pointing deteriorated joints in marble.
- 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).
- American Society for Testing and Materials (ASTM) www.astm.org
- American National Standard Institute (ANSI) www.ansi.org (use most recent versions).
- Setting Materials: Joints should be filled to match existing mortar or marble color, as directed by Regional Historic Preservation Officer (RHPO).
- Portland Cement: ANSI/ASTM C 150, Type I, except complying with staining requirements of ASTM C 91 for not more than 0.03% water soluble alkali
- Hydrated Lime: ANSI/ASTM C 207, Type I
- Sand: ANSI/ASTM C 144, non-staining, except graded with 100% passing the No. 166 sieve for 1/4" and narrower joints
- For white pointing mortar and grout, furnish natural white sand or ground white stone complying with specified requirements
- For colored pointing mortar and grout, furnish ground marble, granite or other sound stone, meeting specified grading requirements for sand, of color required to match existing mortar and grout color
- Clean, potable water
- Dry-Set Mortar: Factory-sanded Portland cement and additives complying with ANSI A 118.1, of type approved by mortar manufacturer and marble supplier for application indicated
- Molding Plaster: ANSI/ASTM C 59
- Clean, potable water
- Masonry Drill
- Hacksaw Blade
- Chisel and mallet for removing deteriorated grout
- Brushes: Soft bristled nylon only
- Hand-held Water Bottle
- Steel Trowel
- Protection: Prevent mortar used in repointing and repair work from staining face of surrounding marble and other surfaces. Remove immediately mortar in contact with exposed marble and other surfaces.
3.02 ERECTION, INSTALLATION, APPLICATION
- Carefully remove deteriorated mortar from joints by hand with a chisel and mallet and other hand tools, unless otherwise indicated and approved by RHPO.
- Clean marble surfaces within raked-out joints to provide reveals with square backs and to expose marble for contact with pointing mortar. Brush, vacuum or flush joints to remove dirt and loose debris.
CAUTION: BE CAREFUL NOT TO SPALL EDGES OF MARBLE UNITS. EPOXY PATCH ANY EXISTING MARBLE UNITS WHICH BECOME DAMAGED. SEE 04455-03-R FOR EPOXY PATCHING PROCEDURES.
- Fill joints in marble unit with new mortar of color to match existing mortar color or to match marble color as directed, except at expansion and control joints indicated to be filled with sealant. Color of mortar shall be established in mock-ups. Finish mortar flush with finished surface of marble, or replicate the original pointing style of mortar. D. Fill all gaps and skips to produce a finished joint which is uniform in color, smooth and without voids, pinholes, or low spots.
- Remove mortar spillage from face of marble as work progresses.
- Cure mortar by maintaining in a moist condition for 7 days.
- For Regrouting Stone Floors: Do not permit traffic during setting of units or for at least 24 hours after final grouting of joints.