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Historic Preservation - Technical Procedures

Spectitle:

Pointing Granite Step Joints

Procedure code:

0446527R

Source:

National Capitol Region Specifications - Customs Svc Bldg

Division:

Masonry

Section:

Granite

Last Modified:

02/24/2012

Details:

Pointing Granite Step Joints



POINTING GRANITE STEP JOINTS


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on pointing grani= te step
         joints with sealant protected by 1/2&quo= t; of pointing mortar.
         This is recommended for joints on horizo= ntal or sloping
         surfaces that are frequently washed with water.  A backer
         rod is typically used in conjunction with sealant in
         joints 3/8" or wider.

    B.   This procedure should be used in conjunction with 04520-
         02-R, which describes in more detail the purpose of
         repointing in general, the materials required and
         precautions that should be taken.

    C.   For guidance on caulking granite steps with waterp= roof
         joint sealant, see 04465-07-R.

    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 Precaution= s

         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

    D.   American Society for Testing and Materials (ASTM), 100
         Barr Drive, West Conshohocken, PA 19428, (610) 832-9585
         or FAX (610) 832-9555.

1.03 QUALITY ASSURANCE

    A.   Certificates: Prior to delivery, submit certificat= es
         attesting to compliance with applicable specifications
         for grades, types and classes.

    B.   Joint Raking: Prior to raking out all areas, cut back
         joints at location selected by Contracti= ng Officer using
         the methods specified. Raking will conti= nue at no
         additional cost to the Government, until an acceptable
         sample is achieved. This area will serve as standard for
         joint raking for the entire job.  It will be marked with
         masking tape and left unpointed until all other pointing
         is complete. Point when directed by the Contracting
         Officer.

    C.   Sample Stone Pointing: Repoint joints, using mater= ials
         and methods specified at a location selected by the
         Contracting Officer.  The samples accepted by the
         Contracting Officer will serve as a standard for the
         entire job.  They will be marked with tape and left
         undisturbed.

1.04 PROJECT/SITE CONDITIONS

    A.   Environmental Requirements: No stone pointing or repair
         shall be performed when the air temperat= ure or stone
         surface temperature is 40 F, and falling during and for
         48 hours subsequent to laying.


PART 2---PRODUCTS

2.01 MATERIALS

    A.   Joint Sealant:

         1.   Multi-part, non-sag urethane sealant in conformance
              with ASTM C290, Type M, Grade NS, Class 25.

         2.   Joint Primer: Provide joint primer recommended by
              the sealant manufacturer for specific application
              and locations.

    B.   Backing Rod: Round, closed cell, polyethylene foam
         backing rod. Use as recommended by the sealant
         manufacturer for back-up and compatibili= ty with sealant.

    C.   Mortar for Granite Pointing:

         1.   Portland Cement: Type 1, ASTM C150, gray.

         2.   Hydrated Masons Lime: ASTM C207, Type S.

         3.   Aggregate: ASTM C144, clean, sharp sand free of
              loam, silt soluble salts and vegetable matter.
              Aggregate shall conform to the following size
              gradations:

                   Sieve Size               Percent Passing

                   No.  4                   100
                   No.  8                   100
                   No.  16                  85 - 95
                   No.  30                  40 - 60
                   No.  50                  15 - 20
                   No.  100                 1 - 5

         4.   Water: Clean and free of delet= erious amounts of
              oil, acid, alkalis and organic matter.

2.02 MIXES

    A.   Proportions for Granite Pointing:

         1.   Portland Cement: 1 part by volume.
         2.   Lime: 1 party by volume.
         3.   Aggregate: 3 parts by volume.<= br>          4.   Water: to form a workable consistency.

    E.   Mixing Procedures: (see also 04100-03-S for additi= onal
         guidance)

         1.   Measure materials by volume or equivalent weight.
         2.   Do not measure by shovel. Use known measure.
         3.   Mix ingredients in clean mecha= nical batcher for 3-5
              minutes.
         4.   Let mortar sit for 20 minutes prior to use to allow
              for initial shrinkage. Use mortar within 1=AB hours
              of initial mixing.


PART 3---EXECUTION

3.01 ERECTION, INSTALLATION, APPLICATION

    A.   Rake out all stone joints in designated areas by hand
         using a chisel =AC" or less in widt= h. Remove all unrequired
         metal fasteners from granite and granite joints.

    B.   Clean all mortar from surfaces within the joint or crack
         so that the new pointing mortar bonds to the building
         material, not old mortar.  Do not chip or spall edges of
         the stone.  More than one =AB" chip per square yard will be
         unacceptable. If work is found unaccepta= ble, all raking
         will cease without additional cost to the Government
         until deficiencies in tools, workers or methodologies
         have been corrected to the Contracting Officer's
         satisfaction.

    C.   Rake joints to a depth to allow for the top of the
         sealant to be =AB" below the face of the granite.

    D.   Brush, vacuum or flush joints to remove all dirt and
         loose debris.

    E.   Reduce initial absorption of the stone by thorough= ly
         wetting stone surface with clean water just prior to
         repointing. Do not allow water to pool on surface of the
         stone.

    F.   Prime or seal joint surfaces where recommended by the
         sealant manufacturer. Confine to areas of sealant bond,
         do not allow spillage or migration onto adjoining
         surfaces.

    G.   Accurately place top of backing rod to a depth equal to
         =AB" plus =AB the width of the join= t.
   
    H.   Apply the sealant recessed =AB" below the sur= face of the
         granite. Tool joint and allow sufficient time for sealant
         to obtain initial set.

    I.   Prior to pointing remaining =AB" of joint, dampen joint to
         lessen initial absorption of the stone by thoroughly
         wetting stone surface with clean water. Do not allow
         water to pool on surface of the stone.
    J.   Pack joints with mortar leaving no voids.

    K.   Use clean tools and equipment, free from hardened or
         partially set mortar.

    L.   Clean excess mortar from stone and joints, removin= g
         splashed mortar and droppings immediatel= y.

    M.   Do not retemper or use mortar which has partially set, is
         caked, or is lumpy.

    N.   Tool horizontal and vertical face joints flush, dense and
         smooth after mortar has taken initial set. Do not allow
         mortar to extend over the stone surface.=

    O.   Curing: Keep joints damp (90% RH) for at least 72 hours
         or until surface is cured. Protect joints from rapid
         drying due to wind (i.e., covering with tarps).

3.02 ADJUSTING/CLEANING

    A.   At the time of pointing of the stone, immediately remove
         mortar, grout and sealant from the face of the masonry.

    B.   Use only tools and equipment which are clean and free of
         hardened or partially hardened material.=

    C.   Clean stone only with fiber bristle brushes and water.
         Use no acids, detergents, or other clean= ing agents.

                        END OF SECTION