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Historic Preservation - Technical Procedures

Spectitle:

Waterproofing Masonry Joints Using Molten Lead, Lead Wool Or A Proprietary Lead Cap System

Procedure code:

0452001R

Source:

Outdoor Sculpture Manual - Cpb

Division:

Masonry

Section:

Masonry Restoration

Last Modified:

11/30/2012

Details:

Waterproofing Masonry Joints Using Molten Lead, Lead Wool Or A Proprietary Lead Cap System



WATERPROOFING MASONRY JOINTS USING MOLTEN LEAD, LEAD WOOL OR A
PROPRIETARY LEAD CAP SYSTEM


THIS PROCEDURE USES LEAD, A HIGHLY TOXIC SUBSTANCE.  THE WORKPLACE
MUST BE ADEQUATELY PROTECTED TO PREVENT INGESTION OF LEAD BY
WORKERS, OR THE SPREAD OF LEAD BEYOND THE WORK SITE.  ALL
ENVIRONMENTAL LAWS MUST BE FOLLOWED CONCERNING CLEAN-UP AND
DISPOSAL OF WASTE MATERIALS.


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure provides guidance on waterproofing masonry
         joints using molten lead, lead wool (similar to steel
         wool), or a proprietary lead capping system which uses
         appropriate caulks or sealants.  

         1.   Leading joints is a traditional technique of
              filling joints to obtain the maximum possible
              waterproofing.

         2.   Molten lead and lead wool are often called lead
              caulk.

    B.   Leading, in one of these three forms, is most commonly
         found, and appropriately used for:

         1.   Joints between stone units in the same plane, i.e.
              coping joints and balustrades; cross joints on
              cornices and belt courses; top joints on window and
              door lintels, entrance porticos, brackets,
              pilasters, watertables and any other piece of
              masonry which projects beyond the face of the
              building.

         2.   Joints between stone units set approximately at
              right angles to each other, i.e. at parapet or side
              walls, or at stair risers and treads.

         3.   Expansion and control joints.

         4.   Anchor holes, i.e. iron fence members into masonry
              or concrete.

         5.   Reglets - horizontal reglets generally filled with
              molten lead, vertical generally with lead wool.
              (Molten lead should NOT used where lead wedges are
              also used to help secure flashing into reglet.)

    C.   Safety Precautions:  Provide protective clothing to
         workers to protect them from extremely high temperatures
         of molten lead.

    D.   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).


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   Weathercap, Inc.
         www.weathercap.net

 

   B.   Nuclead
         www.nuclead,com
                  
        
    C.  Dow Corning Corporation
         www.dowcorning.com

    D.   GE Silicones
         www.ge.com


    D.   H.B. Fuller Automotive Technical Systems
         www.hbfuller.com

2.02 MATERIALS

    A.   Pure Lead:  Available in 5-lb. bars at plumbing supply
         centers (NOT hardware superstores).

    B.   Lead Wool:  Available at plumbing supply centers.

    C.   "Weathercap Type A (Flat) or Type B (90o Cove) Cap" as
         required by joint being sealed, or approved equal.

    D.   Exterior grade caulk as appropriate for type of joint
         being sealed (for use with Weathercap or Nuclead), such as "Corning
         790" or "Corning 791" (Dow Corning), "Ultraglaze 400" or
         ""Silpruf 2000" (GE Silicones), "PTI 738", "PTI 707" or
         "PTI 7130" (H.B. Fuller Automotive Technical Systems), or
         approved equal.

2.03 EQUIPMENT

    A.   Heat-proof crucible and source of heat to bring solid
         lead to melting point of 621degrees F (320 degrees C).

    B.   Ladle to pour molten lead into joint.

    C.   Hammer and chisels (variety of sizes) for packing lead
         wool into joints.

    D.   Hack saw (18T x 12 inch. blade), pliers and clippers to
         cut, notch and bend lead cap as required by installation.


PART 3---EXECUTION

3.01 PREPARATION

    A.   Protection:

         1.   Work must be done on a warm day, while the masonry
              itself is warm, so that extreme high temperature of
              molten lead does not cause masonry to crack.

         2.   Make sure masonry is completely dry.

         3.   If using proprietary capping system, measure width
              of joint to determine width of cap required.  Width
              required equals measurement of joint opening, plus
              the maximum percentage of joint movement
              experienced per scribe test, plus 1/4-inch.

3.02 ERECTION, INSTALLATION, APPLICATION

    A.   Waterproofing with Molten Lead (horizontal joints only)
         and Lead Wool:

         1.   Rake and clean joints of all loose mortar and
              debris.

         2.   For long joints or reglets into which molten lead
              is to be poured, temporarily plug ends with heat
              resistant material.

         3.   Pour molten lead, or pack lead wool tightly, into
              joint to seal.  If molten lead is being used to
              waterproof the joint between a stone base and an
              iron picket or newel, make sure bottom of hole has
              lead in it before setting iron piece.

    B.   Waterproofing Using a Proprietary Lead Capping System:

         1.   Rake and clean joint(s).

         2.   Mark off width of cap onto masonry.

         3.   Apply 1-inch wide masking tape along marks.

         4.   Using a clean, dry cap piece, cut, notch and/or
              miter sections of cap as required to fit joint.

              a.   Outside angles:  notch anchor shaft of cap
                   piece a full 90 degree and bend to fit angle of
                   masonry being sealed.

              b.   Inside angle:  make single cut in anchor shaft
                   and bend to fit angle of masonry being sealed.

              c.   Outside curves:  notch anchor shaft at
                   intervals to allow cap to fit curve.

              d.   Inside curves:  make straight cuts in anchor
                   shaft at intervals to allow cap to fit curve.

         5.   Pre-fit and contour cap after cutting or notching
              anchor shaft to fit joint.  Lift cap out of joint
              and apply metal primer to cap, if required by
              sealant manufacturer.  Allow to dry until tacky.

         6.   Seat foam backer rod into masonry joint to proper
              compressed depth.

         7.   Prime masonry if required by sealant manufacturer.
              Allow to dry until tacky.

         8.   Apply small bead of sealant/caulk to tacky metal
              surface to prevent air entrapment when seated in
              place.

         9.   Fill masonry joint to approximately 1/8-inch above
              face of stone with sealant/caulking compound.

         10.  Set cap in place, pressing firmly into sealant/
              caulking compound for seating and shaping.  Turn
              down at all angles and edges.

         11.  Remove excess sealant/caulking compound with a
              putty knife, being careful not to get excess on
              masonry and leaving finished joint neat and clean.

         12.  Remove masking tape.

                         END OF SECTION
 


waterproofing masonry joints, molten lead on mortar joints, lead wool for mortar joints, lead caps for mortar joints