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.
EPOXY PATCHING CRACKS IN TERRAZZO FLOORS
A. This procedure includes guidance on patching cracks in terrazzo with epoxy resin.
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
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. NTMA Standards: Comply with specified provisions and recommendations of the National Terrazzo and Mosaic Association, Inc. (NTMA)
A. Patching Resin: Manufacturer's standard 2-component epoxy resin, designed specifically for patching of terrazzo materials.
1. Tint to match color of existing terrazzo matrix following manufacturer's recommendations.
B. Aggregate for Epoxy: Natural, sound, crushed marble chips without excessive flats or flakes, complying with NTMA requirements.
1. Colors and gradation of aggregate sizes as required to match existing terrazzo aggregate material.
NOTE: ORIGINAL PLANS OFTEN CONTAIN THE EXACT TERRAZZO MIX.
2. Aggregate colors should be matched after cleaning or taken from the interior of core samples depending upon scope of work.
C. Ammonia or chemical stripper
D. Interior Floor Sealer: Colorless, slip and stain resistant penetrating sealer with Ph factor between 7 and 10, that does not affect color or physical properties of terrazzo surface.
E. Clean, potable water
A. Hand sander, small grinding tools
B. Grinding stones: Fine grit emery stones manufactured specifically for restorative type grinding and surfacing of terrazzo surfaces (#40 and #80 grit stones).
C. Resurfacing Screens: A fine grit screen manufactured specifically for restorative type grinding and resurfacing terrazzo surfaces.
3.01 ERECTION, INSTALLATION, APPLICATION
A. Remove all foreign matter from the void, followed by routing with a power tool. Remove all sealer from the surface adjacent to the void with a stripper or ammonia.
B. Blend the resin materials to match the color matrix, by adding marble dust or pigment.
C. Force mixed resin into the void, making sure it is pressured into the crack as deep as possible. In some cases, the supplier will instruct using a primer for their materials.
D. If the void is large enough, and the intent is to disguise the line so it will blend into the rest of the terrazzo floor, irregularly place marble chips matching the existing terrazzo blend along the line approximately one to two inches on center. Be sure to do this, however, while the patching resin is still in a wet state. Finally, tool off surface and allow to cure.
E. When the material has hardened, sand surface with a hand sander or small grinding tool, using fine stones.
1. Use a #40 or finer grit stone for the initial grinding, exposing the marble chips. Follow with a fine #80 grit stone before grouting with cement to fill all pinholes.
CAUTION: DIVIDER STRIPS MAY BE COATED INSTEAD OF SOLID COMPOSITION. COATED STRIPS SHOULD NOT BE GROUND. GRINDING MAY CAUSE COATED DIVIDER STRIPS TO LOSE THEIR COATING AND DISCOLOR.
2. Cover grouted surface with paper or polyethylene for at least 72 hours.
3. Thoroughly rinse the surface with clean, clear water.
4. Remove excess rinse water and allow to dry.
5. Final polish with a #80 or finer grit stone. Care should be taken to limit grinding and polishing to a small distance beyond the perimeter of the patch.
6. For some time, this area will be noticeable, however, with normal maintenance, the area will blend into the balance of the floor.