GSA Mobile

CAULKING GRANITE STEPS WITH WATERPROOF JOINT SEALANT


THE PREFERRED METHOD OF SEALING JOINTS IS THE PROPER REPOINTING
WITH COMPATIBLE HISTORIC MORTAR MIX (SEE 04100-03-S AND 04250-02-R
FOR GUIDANCE).  HOWEVER, WHEN THIS IS NOT FEASIBLE OR A SHORT TERM
SOLUTION IS NEEDED, THE FOLLOWING APPROACH IS ACCEPTABLE.


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on removing deteriorated
         sealant from horizontal granite joints and recaulking
         with a waterproof joint sealant.  This procedure
         specifically applies to exterior granite steps, although
         use on other horizontal surfaces may be appropriate.

    B.   For general information on the characterics, uses and
         problems associated with sealants, see 07900-02-S.  For
         guidance on selecting masonry joint sealants, see 07900-
         01-S.

    C.   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).

1.02 REFERENCES

    A.   American Society for Testing and Materials (ASTM), 
         www.astm.org
         


PART 2---PRODUCTS

2.01 MATERIALS

    A.   Joint sealant:  Multi-part, non-sag urethane sealant
         conforming with ASTM C290, Type M, Grade NS, Class 25.

    B.   Joint primer:  Provide as recommended by sealant
         manufacturer.

    C.   Backer rod:  Round, closed cell, polyethylene foam
         backing rod; should be compatible with sealant; use as
         recommended by sealant manufacturer.

2.02 EQUIPMENT

    A.   Stiff natural fiber or nylon bristle brushes

    B.   Striking hammer or "No-bounce" hammer

    C.   Joint chisel


PART 3---EXECUTION

3.01 ERECTION, INSTALLATION, APPLICATION

    A.   Rake out old sealant or mortar from joints by hand using
         a hammer and chisel.  Rake to expose sound mortar.  See
         also 04520-02-R for guidance on raking out joints.

         NOTE:  DO NOT USE MECHANICAL METHODS TO CUT OUT JOINTS,
         DUE TO THE HIGH PROBABILITY OF DAMAGING THE STONE.  TAKE
         CARE NOT TO CHIP OR SPALL EDGES OF ADJACENT STONE.

    B.   Remove loose dirt and debris from the joint using a stiff
         bristle brush or vacuum.

    C.   Prime joint surfaces as recommended by the sealant
         manufacturer.  Protect adjacent surfaces from spillage or
         spattering of sealant.

    D.   Insert backing rod to a depth equal to 1/2 the width of
         the joint.

    E.   Fill joint with sealant.  Tool joint within 10 minutes of
         placing.  Finish joint level with the stone surface.  

    F.   Remove excess sealant from the stone surface immediately.

                         END OF SECTION