Installing Lead Stone Flashing To Protect Masonry Joints
- CSI Division:
- Division 3 - Concrete
- Lead Flashing
- Last Modified:
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.
- This procedure includes guidance on weatherproofing vulnerable masonry joints by embedding a soft lead strip into a caulking compound/sealant filled joint.
- This type of work is often necessary when unknown building movement causes the failure of existing joint caulk/sealant in locations such as a masonry/stone parapet, coping, balustrade, railing, cornice, belt course ledges, or any other exterior masonry/stone features where the top surface is exposed. This also includes corner and fillet joints where a horizontal surface joins to a vertical surface; with horizontal protection to extend down over front and back edges 2" or to an appropriate stopping point to protect the exposed corner.
- See 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections:
- Safety Precautions
- Historic Structures Precautions
- Quality Assurance
- Delivery, Storage and Handling
- Project/Site Conditions
- Sequencing and Scheduling
- 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).
1.02 SYSTEM DESCRIPTION
- Stone flashing is a weatherproofing product, manufactured from lead, which is designed to be used with a building sealant for the weatherproofing and protection of masonry joints. It consists of a molded cap or fillet surface with a splined tang for anchoring in the sealant filled mortar joint; manufactured in a selection of sizes, and in continuous strips for field cutting and fitting.
- Manufacturers' information, shop drawings (manufacturer's standard detail sheets), materials lists and certificates for the products proposed for use.
- Samples: 12" long pieces of each type of stone flashing proposed for use.
1.04 QUALITY ASSURANCE
- Restoration Specialist: Work must be performed by a firm having not less than 5 years successful experience in comparable masonry restoration projects and employing personnel skilled in the restoration processes and operations indicated.
- Provide copies of all manufacturer's guarantees of materials and installation, duly signed and dated.
- Include all warranty inspections by a manufacturer's representative necessary to effect the guarantee of material performance and its installation.
- Weathercap, Inc. www.weathercap.net
- NucLead www.nuclead.com
- Tee Caps: Lead Stone Flashing strips (Weathercap, Inc., NucLead), or approved equal.
- Use size of strips as recommended by sealant manufacturer and compatible with style and configuration of existing.
- Strips should be of sufficient size to cover the joint width, plus a percentage allowance for anticipated joint movement, plus 1/4".
- Sealant: As recommended by Tee Cap manufacturer. See also 07900-01-S for guidance. Test to make sure sealant does not stain masonry.
- 1" masking tape
- Putty knife
- Heavy gloves
- Determine the extremes of joint movement using a scribe kit (available from sealant manufacturer); measurement of anticipated and known joint movement is necessary in determining the appropriate size of tee cap to use.
- Verify that joints to have stone flashing strips are raked or cut out to the correct depth and clean.
3.03 ERECTION, INSTALLATION, APPLICATION
NOTE: WEAR GLOVES WHEN WORKING WITH LEAD PRODUCTS AND WASH HANDS THOROUGHLY WHEN FINISHED WITH WORK.
- Fitting Tee Cap:
- Mark off width of selected tee cap on the masonry/stone surface and apply 1" masking tape lateral to marks.
- Pre-fit or shape and cut tee cap strips to closely conform to the profile of the stone substrate as required before setting.
- Select width to overlap joint edges not less than 1/8".
- Cut strips to lay in a single full length of each joint wherever possible with an end turn-down over front and back faces of ledges and copings a minimum of 1" or to drop edge.
- Make all joints in tee cap neatly mitered, coped, or butted to produce close fitting, weather resisting joint protection; notch strips as recommended by manufacturer.
- Apply metal primer to tee cap if required.
- Sealing and Installing Tee Cap: Install sealants in accordance with manufacturer's recommendations.
- If required, install backer rod to a depth of 1/4" below tip of anchor shaft when tee cap is set in place.
- Prime stone, if required.
- Fill joint with sealant to a height of approximately 1/8" above the adjacent masonry surface. Follow manufacturer's instructions.
- Set preformed tee cap strip into the sealant bed, pressed down firmly to the stone surface so bonding grooves are solidly filled and no voids exist between tee cap and masonry.
- Clean off excess sealant compound using a putty knife and leave adjacent masonry clean.
- Carefully remove masking tape from adjacent >surfaces.