Replacing Deteriorated Caulk At Masonry Surfaces

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.



A. This procedure includes guidance on caulking all joints on horizontal or sloping existing masonry surfaces including, but not limited to: cornices, parapets, window sills, platforms steps and other wash surfaces.

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
  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).


A. The following publications of the issues listed below, but referred to thereafter by basic designation only, form a part of this specification to the extent indicated by references thereto:

  1. TT-S-001543A Sealing Compound, Silicone Rubber Base (for (COMM-NBS) Caulking, Sealing and Glazing in Buildings and Other Structures).
  2. UU-T-00106D Tape, Pressure-Sensitive Adhesive, Masking, Paper.


A. General: Caulking or sealant shall be provided in joints as indicated or specified. Materials shall conform to the respective specifications and other requirements specified. The work specified herein shall be performed by workers skilled in such work.

B. Sealant Formulation Intended Application: Each container brought to the jobsite shall be marked for the intended use. The color shall be one of the manufacturer's standard colors as closely matching the adjacent surfaces as possible. The sealant formulation shall conform to the requirements specified herein.

C. Thinners or other additives shall not be used to modify the formula.


A. Samples:

  1. Materials: Prior to delivery of the caulking and sealant to the jobsite, a one-cartridge or equivalent representative sample of the caulking and sealant specified herein shall be furnished. The sample shall be accompanied by certified laboratory test reports showing that the caulking and sealant to be furnished have been tested within the last 12 months and meet the requirements of the applicable specifications. The sample container shall include the same information on the label as specified herein for containers delivered to the job.
  2. Joints: Before work is started, a sample of each type of joint shall be caulked or sealed where directed. The samples shall show the materials, workmanship bond, and color of materials as specified or selected for the work. The materials, workmanship, bond, and color throughout the project shall match that of the approved sample joint.


A. Packing and Shipping: Materials shall be delivered to the job in the manufacturers' original unopened containers. The containers shall include the following information on the label: supplier, name of material, formula or specification number, lot number, color, date of manufacture, mixing instructions, shelf life, and curing time when applicable at the standard conditions for laboratory tests. All materials shall be carefully handled and stored to prevent inclusion of foreign materials, or components outdated as indicated by shelf life shall not be used.


A. Environmental Requirements: The ambient temperature shall be within the limits of 40 and 90 F when the caulking and sealants are applied.



A. Sealant shall be a cone-component, elastomeric-type compound conforming to TT-S-1543, class A. The compound shall be supplied in a ready-to-use form which requires no on-the-job mixing.

B. Backup material shall be closed-cell polyethylene foam. Backup material shall be nonabsorbent, nonstaining, and compatible with the sealant used. Tube or rod stock when used shall be rolled into the joint cavity.

C. Bond-preventive materials shall be one of the following, as recommended by the sealant manufacturer.

D. Polyethylene Tape, Pressure-sensitive Adhesive: The adhesive is required only to hold tape to the construction materials as indicated.

E. Masking tape shall conform to UU-T-106.



A. Surface Preparation:

  1. The joint design, shape, and spacing shall be as indicated by the RHPO. The surfaces of joints to be sealed shall be dry. Oil, grease, dirt, chalk, particles or mortar, dust, loose rust, loose mill scale, and other foreign substances shall be removed form all joint surfaces to be sealed. Oil or grease shall be removed with solvent and surfaces shall be wiped with clean cloths.
  2. Concrete and Masonry Surfaces: Where surfaces have been treated with curing compounds, oil, or other such materials they shall be removed by wire brushing. Laitance, efflorescence and loose mortar shall be removed from the joint cavity.
  3. Steel surfaces to be in contact with sealant shall be scraped and wire brushed to remove loose mill scale. Protective coatings on steel surfaces shall be removed by a solvent that leaves no residue.


A. Joint Types and Sealants: Unless otherwise specified, for all joints requiring sealant on horizontal or sloping surfaces. The joint shapes and sizes shall be indicated below unless otherwise specified:

Sealant (No.) (Type) Sealant Form
TT-S-001543A Type II Ready to Use

B. Paper masking tape shall be placed on the finish surface on one or both sides of a joint cavity to protect adjacent finish surfaces from primer or compound smears. Masking tape shall be removed within ten minutes after joint has been filled and tooled.

C. Bond-preventive materials for rubber-base sealant shall be installed on the bottom of the joint cavity and other surfaces indicated to prevent the sealant from adhering to the surfaces covered by the bond-preventive materials. The materials shall be carefully applied to avoid contamination of adjoining surfaces or breaking bond with surfaces other than those covered by the bond- preventative materials. At the option of the Contractor, backstop material with bond-breaking characteristics may be installed in lieu of bond-preventive materials specified.

D. Backstops: The back or bottom of joints constructed deeper than indicated shall be packed tightly with backstop material to provide a joint of depth indicated.

E. Elastomeric Type Sealant: Compound shall be gun-applied with a nozzle of proper size to fit the width of joint indicated and shall be forced into grooves with sufficient pressure to expel air and fill the groove solidly. Sealant shall be uniformly smooth and free of wrinkles. Joints shall be tooled slightly concave after sealant is installed. When tooling white or light-color sealant, dry or water-wet tool shall be used.


A. The surfaces adjoining the caulked and sealed joints shall be cleaned of smears and other soiling resulting from the caulking and sealing application as work progresses.