Replacing Joint Sealants Between Architectural Bronze Window Frames And Exterior Stone Masonry

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 replacing damaged or deteriorated joint sealants between heads, jambs, and sills of architectural bronze window frames and exterior stone masonry.
  2. Architectural Bronze is an alloy of copper, commonly composed of approximately 57% copper (Cu), 40% zinc (Zn) and 3% lead (Pb); it is actually a “leaded brass”.
  3. For general information on the characteristics, uses and problems associated with bronze (including architectural bronze, see 05010-03-R.
  4. 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. American Society for Testing and Materials (ASTM), 100 Barr Drive, West Conshohocken, PA 19428, 610-832-9585 or FAX 610-832-9555.


  1. System Performances: Provide joint sealers that have been produced and installed to establish and maintain watertight and airtight continuous seals.


  1. Product date from manufacturers for each joint sealer product required, including instructions for joint preparation and joint sealer application.
  2. Samples of Initial Selection Purposes: Submit three (3) samples of the following items:
    1. Caulking compound; after Contracting Officer’s Representative selection from manufacturer’s color chart, submit three (3) tubes.
    2. Pre-molded filler; submit three (3) segments, 12” minimum length.
  3. Certificates from manufacturers of joint sealers attesting that their products comply with specification requirements and are suitable for the use indicated.
  4. Qualification data complying with requirements specified in Quality Assurance article. Include list of completed projects with project name, names of Architects and Owners, addresses and telephone numbers.
  5. Sample Mock-Ups for Verification Purposes: Prior to installation of joint sealers, apply elastomeric sealants to each type of joint (3’ minimum length) for further verification of colors selected from sample submittals and to represent completed work for qualities of appearance, materials, and application. Locate mock-ups as directed by Contracting Officer.


  1. Installer Qualifications: Engage an installer who has successfully completed within the last 5 years at least 3 joint sealer applications similar in type and size to that of this project.
  2. Single Source Responsibility for Joint Sealer Materials: Obtain joint sealer materials from a single manufacturer for each different product required.
  3. Preconstruction Compatibility and Adhesion Testing: Use test methods standard with manufacturer to determine if priming and other specific joint preparation techniques are required to obtain rapid, optimum adhesion of joint sealers to joint substrates. Perform tests under normal environmental conditions that will exist during actual installation.


  1. Packing and Shipping: Deliver materials to project site in original unopened containers or bundles with labels informing about manufacturer, product name and designation, color, expiration period for use, pot life, curing time and mixing instructions for multi component materials.
  2. Storage and Protection: Store and handle materials to prevent their deterioration or damage due to moisture, temperature changes, contaminants, or other causes.


  1. Environmental Requirements: Do not proceed with installation of joint sealers when ambient and substrate temperature conditions are outside the limits permitted by joint sealer manufacturer or below 40 F or when joint substrates are wet due to rain, frost, condensation, or other causes.


  1. All work under this section shall be guaranteed for not less than five (5) years from the date of final acceptance by the Government against leaks and weather penetration.



  1. Dow Corning Corporation 1225 Northmeadow Parkway, Ste. 104 Roswell, GA 30076 404/751-7979
    P.O. Box 994 Midland, MI 48686-0994 517/496-4000
  2. General Electric Co. Waterford, NY 12188 518/237-3330
  3. Pecora Corporation 165 Wambold Road Harleysville, PA 19438 800/522-1285 or 215/723-6051

    2601 Oakland Avenue Garland, TX 75041 800/523-6688 or 214/278-8158
  4. Tremco, Inc. 3735 Green Rd. Beachwood, OH 44122 800/321-7906


NOTE: Chemical products are sometimes sold under a common name. This usually means that the substance is not as pure as the same chemical sold under its chemical name. The grade of purity of common name substances, however, is usually adequate for stain removal work, and these products should be purchased when available, as they tend to be less expensive. Common names are indicated below by an asterisk (*).

A. General:

  1. Compatibility: Provide joint sealers, joint fillers and other related materials that are compatible with one another and with joint substrates under conditions of service and application, as demonstrated by testing and field experience.
  2. Colors: Provide color of exposed joint sealers indicated or, if otherwise indicated, as selected by the Contracting Officer from manufacturer’s standard colors.

B. Silicone Sealant: One-part silicone-based, non-sag, elastomeric sealant, complying with ASTM C920, Type S, Class 25, Grade NS, such as “Dow Corning 790” (Dow Corning Corp.), “Silpruf SCS2000 Sealant” (General Electric Co.), or approved equal.

C. Polyurethane Sealant: One-part polyurethane-based sealant; complying with ASTM C920, Type S, Class 25. Use self-leveling type for joints of floors and pavements, such as “Dynatrol 1” (Pecora Corp.), “Dymonic” (Tremco, Inc.), or approved equal.

D. Miscellaneous Sealant Materials:

  1. Joint Primer/Sealer: Provide type recommended by sealant manufacturer for joint surfaces to be primed or sealed.
  2. Bond Breaker Tape: Provide plastic tape as recommended by sealant manufacturer for sealant-contact surfaces where bond must be avoided for proper performance of sealant. Provide self-adhesive tape where applicable.
  3. Xylol:
    1. Any of three toxic, flammable, oily, isomeric, aromatic hydrocarbons that are di-methyl homologues of benzene and are obtained from wood tar, coal tar, or petroleum distillates; Also a mixture of xylenes and ethyl-benzene used chiefly as a solvent.
    2. Other chemical or common names include Xylene (C8H10); P-xylene; 1,4-dimethyl benzene.
    3. Potential Hazards: TOXIC AND FLAMMABLE.
    4. Available from chemical supply house, hardware store, paint store or printer’s supply distributor.

      1. A petroleum distillate that is used especially as a paint or varnish thinner.
      2. Other chemical or common names include Benzine*(not Benzene); Mineral spirits; Petroleum spirits*; Solvent naphtha*.
      3. Potential Hazards: TOXIC AND FLAMMABLE.
      4. Safety Precautions:
          2. ALWAYS wear rubber gloves when handling mineral spirits.
          3. If any chemical is splashed onto the skin, wash immediately with soap and water.
      5. Available from construction specialties distributor, hardware store, paint store, or printer’s supply distributor.
  4. Clean, potable water.
  5. Clean, soft cloths.


  1. Caulking gun
  2. Wire brushes (non-ferrous bristles)
  3. Tooling stick or knife



  1. Surface Preparation:
    1. All openings, joints, or channels to be sealed shall be thoroughly clean, dry and free from dust, oil, grease, loose mortar or any other foreign matter.
    2. Masonry surfaces forming sides of joints shall be wire-brushed with non-ferrous brush, then air-blown clear.
    3. Prime or seal joint surfaces where recommended by sealant manufacturer. Confine primer/sealer to areas of sealant bond only.
    4. Set joint fillers without twists, and to allow for bond breakers, backer rods and sealants. Do not leave gaps between ends of joint filler units.
    5. Install sealant backer rod for sealants, except where recommended to be omitted by sealant manufacturer.
    6. Install bond breaker tape where required by manufacturer’s recommendations to ensure that sealants will perform as intended.


  1. Caulking shall be gun-applied through a nozzle opening of such a diameter so that the full bead of sealant is gunned into the joint, filling the joint completely without gaps or air pockets. A superficial or skin bead will not be acceptable.
  2. All beads shall be tooled immediately after application to ensure firm, full contact with the inner faces of the joints. Excess material shall be struck off with a tooling stick or knife, dipped in solvent to avoid tearing or stripping of the bead.
  3. The finished bead shall be flush with the surface, or as otherwise indicated by the Contracting Officer’s Representative.
  4. Provide two weep holes at window lintels, 1’-0” in from each jamb.
  5. Install sealants to depths as recommended by sealant manufacturer to provide uniform shapes which allow optimum sealant movement capability.
  6. Do not allow sealants to spill onto adjoining work. Adjacent surfaces which have been soiled by sealing operations shall be cleaned immediately and left in a clean and neat condition.


  1. Excess compound shall be cleaned off non-porous surfaces while uncured, using a solvent such as commercial xylol or Naphtha. On porous surfaces, the excess sealant should be allowed to cure and be removed by non-abrasive mechanical means approved by the Contracting Officer’s Representative.
  2. Remove all rubbish, cartons and debris resulting from caulking operations daily during the performance of the work.