Terrazzo Repair and Restoration Details

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I found the following website very informative.

http://ncr.gsa.gov/HistoricPreservation/htmldoc/43rmtf.asp

Restoring A Terrazzo Floor

Over time, a terrazzo floor may need restoration work to repair any damage and restore the surface finish. Restoration of a terrazzo floor requires professional technicians and special procedures.

Refinishing Discolored or Damaged Terrazzo Floors

Older terrazzo floors may be discolored or have a damaged surface because of a build-up of old finishes or soap scum, overuse of disinfectants and coatings, or because of dirt tracked into the floor. These floors should be stripped to the original surface, cleaned, and then sealed.

1. Determine type of terrazzo and select appropriate products.
2. Always wear protective gear and work in well-ventilated area when handling any chemicals.
3. Test an area of each terrazzo type before stripping, cleaning, and sealing all the terrazzo.
4. Avoid contact of chemicals with adjacent surfaces.
5. Strip existing sealers and coatings from floor.
* Use neutral liquid chemical cleaner with a pH factor between 7 and 10, formulated for the specific type of terrazzo.
* Following manufacturer's directions, apply chemical floor cleaner and let stand recommended time or time determined by test area.
* Apply a mist of water over the cleaner on the floor.
* Pick up residue with a wet vacuum.
* Using a power scrubber with a scrub brush attachment, fiber bristle brush, or white nylon pad, scrub the floor until all coating material has been removed.
* Pick up all liquid residues with a wet vacuum.
* Thoroughly rinse the surface with clean water.
* Pick up all remaining liquid residues with a wet vacuum and allow floor to dry.
* Do not use metal brushes or steel wool.
* Repeat process if necessary.

6. Clean the surface using a mildly abrasive phosphate free cleaning compound containing no caustic or harsh fillers, formulated specifically for restorative type cleaning of terrazzo.

7. Apply new sealer using a colorless, slip and stain resistant sealer with a pH factor between 7 and 10, that does not affect the color or physical properties of the terrazzo surface.

8. Always use clean water and remove all liquid with a wet vacuum.

See the GSA Historic Preservation Technical Procedures titled, "Stripping And Cleaning Dirty Or Discolored Terrazzo Floors" and "Stripping Built-up Coatings From Terrazzo," found on the GSA web site at http://w3.gsa.gov/web/p/hptp.nsf?OpenDatabase, for detailed information on products, manufacturers, and procedures.

Regrinding Terrazzo Floors

If dirt, scratches, and the build-up of coatings are so severe that normal stripping and cleaning cannot restore the floor, or if the floor is heavily worn, the surface may be stripped using fine grit stones and resurfacing screens. This method involves grinding off a thin layer of the terrazzo and should only be used as an extreme measure. The work must be performed by an experienced professional.

1. Grind and polish the terrazzo floor to produce a clean, smooth, uniform finish.
* Be careful grinding around dividing strips.
* For small areas use hand sander or small grinding tool; for larger areas use a circular buffing machine with grinding and polishing pads.
* Use a #24 or finer grit stone/screen (fine mesh sand may also be used) for the initial grinding, exposing the marble chips. Follow with a fine #80 or finer grit stone/screen.
* Rinse floor thoroughly with clean water and remove excess rinse water.
* Machine or hand-apply grout using matching Portland Cement, filling all voids completely.
* Cover grouted surface with paper or polyethylene for at least 72 hours.
* Final polish with a #80 or finer grit stone until grout has been removed from the terrazzo surface.
* Wash surface with neutral cleaner and thoroughly rinse with clean water. Allow surface to thoroughly dry.

2. Seal terrazzo with a colorless, slip and stain resistant penetrating sealer with pH factor between 7 and 10, that does not affect color or physical properties of the terrazzo.

See the GSA Historic Preservation Technical Procedure titled, "Regrinding Terrazzo Floors," found on the GSA web site at http://w3.gsa.gov/web/p/hptp.nsf?OpenDatabase, for detailed information on products, manufacturers, and procedures.

Repairing Chips and Cracks in Terrazzo

GSA's Historic Preservation Technical Procedures includes guidelines for repairing chips and cracks in terrazzo using either a cement grout or epoxy resin, depending on the original binder used in the terrazzo. It is recommended that minor chips and cracks be repaired only when surface irregularities present safety hazards or when it is necessary to prevent further deterioration to the terrazzo.

Patching Minor Chips and Cracks in Terrazzo with Cement Grout

1. With a power saw or hand tools, cut a vertical perimeter wall around the area to be patched.

2. Clean the surface of debris and saturate the void with water.

3. Apply cement paste and work into surface. Do not allow cement paste to dry before placing terrazzo composition.

4. Mix terrazzo composition, matching marble chips and matrix for existing terrazzo by size, mineral content, and color.

5. Place mixture over chip or crack and level with a trowel.

6. Compact patch, removing all excess water and cement from the surface.

7. Cover the patch with paper or polyethylene sheeting to prevent quick hydration. Cure until topping develops sufficient strength to prevent lifting or pulling of terrazzo chips during grinding.

8. Sand surface with hand sander or small grinding tool, using fine stones to achieve desired finish.
* 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.
* Be careful grinding around dividing strips.
* Cover grouted surface with paper or polyethylene for at least 72 hours.
* Thoroughly rinse the surface with clean water; remove excess water.
* Machine- or hand-apply grout using matching Portland Cement, filling all voids completely.
* 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.

9. Seal patch with a colorless, slip and stain resistant penetrating sealer with pH factor between 7 and 10, that does not affect color or physical properties of the terrazzo.

Epoxy Patching Cracks in Terrazzo Floors

1. 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.

2. Blend the resin materials, matching the color and aggregate size of existing terrazzo.

3. Force mixed resin into the void, making sure it is pressured into the crack as deep as possible. Marble chips can be added to the mixture while it is still wet to match existing terrazzo blend. Tool off surface and allow to cure.

4. When the material has hardened, sand surface with a hand sander or small grinding tool, using fine stones.
* 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.
* Be careful grinding around dividing strips.
* Cover grouted surface with paper or polyethylene for at least 72 hours.
* Thoroughly rinse the surface with clean water; remove excess water and allow to dry.
* 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.
5. For some time, this area will be noticeable, however, with normal maintenance, the area will blend into the balance of the floor.

See the GSA Historic Preservation Technical Procedures titled, "Patching Minor Chips And Cracks In Terrazzo With Cement Grout" and "Epoxy Patching Cracks In Terrazzo Floors," found on the GSA web site at http://w3.gsa.gov/web/p/hptp.nsf?OpenDatabase, for detailed information on products, manufacturers, and procedures.

Installing a New Bonded Terrazzo Floor to Match Historic Terrazzo

If may be necessary to install a new terrazzo floor to replace lost or severely damaged portions of existing terrazzo floors, or to enlarge or alter an area of existing/historic terrazzo flooring. This work requires professional, experienced technicians and special procedures.

Examine the existing floor to determine type of terrazzo in order to match marble chips and matrix by size, mineral content, and color for replication and replacement. Color samples should be taken after existing floor has been cleaned. Thoroughly examine the existing conditions of floor to determine necessary work.

Match the historic character and pattern of the terrazzo in all spaces containing or contiguous with existing terrazzo. Provide terrazzo bases, thresholds, stair treads and landings, without interruptions of seams, except where divider strips, control joints, and expansion joints are required. Place and finish terrazzo around obstructions to achieve continuous color, pattern, and finish.

See the GSA Historic Preservation Technical Procedure titled, "Installing A New Bonded Terrazzo Floor To Match Historic Terrazzo," found on the GSA web site at http://w3.gsa.gov/web/p/hptp.nsf?OpenDatabase, for detailed information on products, manufacturers, and procedures.

For further information on maintaining, cleaning, and restoring terrazzo floors, refer to the GSA Historic Preservation Technical Procedures found on the GSA web site at http://w3.gsa.gov/web/p/hptp.nsf?OpenDatabase. The complete list of topics included:

TERRAZZO:
Terrazzo: Characteristics, Uses And Problems
Routine Preventive Maintenance Guidelines For Terrazzo
Stripping And Cleaning Dirty Or Discolored Terrazzo Floors
Removing Ink Stains From Terrazzo Floors
Removing Lubricating Oil Stains From Terrazzo Floors
Removing Tobacco Stains From Terrazzo Floors
Removing Coffee Stains From Terrazzo Floors
Removing Iodine Stains From Terrazzo Floors
Stripping Built-Up Floor Coatings From Terrazzo
Patching Minor Chips And Cracks In Terrazzo With Cement Grout
Epoxy Patching Cracks In Terrazzo Floors
Regrinding Terrazzo Floors
Installing A New Bonded Terrazzo Floor To Match Historic Terrazzo