Stripping And Cleaning Dirty Or Discolored Terrazzo Floors

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.

PREFACE: The cleaning or removal of stains from masonry may involve the use of liquids, detergents or solvents which may run off on adjacent material, discolor the masonry or drive the stains deeper into the porous masonry. Use the products and techniques described here only for the combinations of dirt/stain and masonry specified.



  1. This procedure includes guidance on stripping and cleaning existing terrazzo which is dirty, has minor damage or has a surface residue from removal of newer materials.
  2. Discoloration of terrazzo may be caused by wax build-up, soap scum, overuse of disinfectant, epoxies and coatings that have yellowed, or by dirt tracked into an unsealed floor.
  3. Historic Structures Precautions: Injurious acids, caustic soda or any ingredient independently or in combination in any compound fluid or solution which will damage the terrazzo shall NOT be used.
  4. See "General Project Guidelines" 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. NTMA Standards: Comply with specified provisions and recommendations
  2. National Terrazzo and Mosaic Association, Inc. (NTMA),


  1. Where current codes cannot be complied with, and/or construction limitations (including deterioration of existing substrate) are such that the intended finish cannot be achieved, notify the Regional Historic Preservation Officer (RHPO) for clarification and/or decision prior to proceeding with the work.
  2. Mock-ups: Strip and clean 20 square feet of each terrazzo type for review by RHPO before stripping and cleaning all the terrazzo.



  1. ProSoCo, Inc.
    Lawrence, KS
  2. BASF Corporation
    Florham Park, NJ


  1. Cleaner: Liquid, neutral chemical cleaner, with pH factor between 7 and 10 of formulation recommended by sealer manufacturer for type of terrazzo used, and complying with NTMA requirements, such as Sure Klean 859 (ProSoCo, Inc.), or approved equal.
  2. 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 ofterrazzo surface.
  3. Compound Cleaner: A mildly abrasive phosphate free cleaning compound containing no caustic or harsh fillers, manufactured specifically for restorative type cleaning of terrazzo surfaces, such as "Wyandotte Detergent" (BASF-Wyandotte Corporation) or approved equal.
  4. Sure Klean Grout and Tile Cleaner (ProSoCo, Inc.), or approved equal.
  5. Clean, potable water


  1. Wet vac
  2. Paint roller
  3. Low pressure tank sprayer
  4. Power scrubber with scrub brush attachment
  5. Stiff bristle brushes (natural or nylon bristle)



  1. Perform a thorough examination of the existing conditions. Perform any necessary tests on an inconspicuous surface to determine the current conditions and appropriate steps and materials necessary for stripping terrazzo surfaces.


NOTE: The following procedure calls for stripping the floor down to the original surface, cleaning if necessary, and then sealing with a long-lasting sealer.

  1. Strip existing sealers and coatings from floor:
    1. Apply chemical floor cleaner with paint roller and let stand for five to ten minutes. Work in areas no more than four feet wide to insure that the applicator is always standing on a dry floor.
    2. Using a low pressure tank sprayer, apply a mist of water over the cleaner already on the floor. The water will emulsify the old sealer and dilute the thixotropic cleaner.
    3. Pick up all remaining residues with a wet vac.
    4. Using a power scrubber with a scrub brush attachment, scrub the floor until all coating material has been removed.
    5. Pick up all liquid residues with a wet vac.
    6. Pick up all remaining liquid residues with a wet vac and allow to dry.
  2. If dirt and scratches have become so severe that normal stripping and cleaning no longer restore the floor to its original luster, the surface may be stripped using fine grit stones and resurfacing screens.
    CAUTION: This method of removing sealers and coatings involves grinding off a thin layer of the terrazzo. It should only be used as an extreme measure and a specialist must be consulted.
  3. If the floor is still dirty, clean using Sure Klean Grout and Tile Cleaner (ProSoCo, Inc.), or approved equal.
    1. Dilute three to four parts water to one part Grout and Tile Cleaner.
    2. Pre-wet area to be cleaned.
    3. Apply cleaning solution with floor scrub brushes.
    4. Let stand two to three minutes while lightly agitating with a stiff, natural bristle brush, broom, or nylon brush.
    5. Thoroughly rinse the surface with clean, clear water.
    6. Pick up all remaining liquid residues with a wet vac and allow to dry.
    7. Seal the terrazzo surface with high strength sealer according to manufacturer's instructions.