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Historic Preservation - Technical Procedures

Spectitle:

Pointing Granite And Filling Cracks

Procedure code:

0446512R

Source:

National Capitol Region Specifications - Customs Svc Bldg

Division:

Masonry

Section:

Granite

Last Modified:

06/14/2012

Details:

Pointing Granite And Filling Cracks



POINTING GRANITE AND FILLING CRACKS<= br>

PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on pointing deteriorated
         joints on vertical granite surfaces.  The procedure
         described may also be used to fill minor cracks in
         granite.

    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.   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

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



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 Contracting Officer using
         the methods specified. Raking will continue 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 materials
         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.  Pointing mortar should match historic in
         appearance, strength and composition.

1.04 PROJECT/SITE CONDITIONS

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


PART 2---PRODUCTS

2.01 MATERIALS

    A.   Mortar For Granite Pointing: Follow manufacturer's=
         printed recommendations for product use and installation.

         1.   Portland Cement: Type 1, ASTM C150, gray or white as

               required to match existing color.

         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 deleterious amounts of
              oil, acid, alkalis and organic matter.

2.02 MIXES

    A.   Proportions for Granite Pointing: Mix/proportions for
         aggregate color and texture should close= ly match
         historic.

         1.   Portland Cement: 1 part by volume.
         2.   Lime: 1 party by volume.
         3.   Aggregate: 3 parts by volume.        

        4.   Water: to form a workable consistency.

    B.   Mixing Procedures: (see also 04100-03-S for additional
         guidance)

         1.   Measure materials by volume or equivalent weight.
         2.   Do not measure by shovel. Use known measure.
         3.   Mix ingredients in clean mechanical 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 no wider that 3/4 (three fourths) joint width.

         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 chip per square yard will be
         unacceptable. If work is found unacceptable, 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.   Joint depth to be at least 3/4", but in all cases rake
         back to expose sound mortar.

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

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

    F.   Pack joints with mortar leaving no voids. Place mortar in
         layers not exceeding 1/4 inch in depth. Apply succeeding layers
         only after preceding layer has taken initial set.

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

    H.   Clean excess mortar from stone and joints, removing
         splashed mortar and droppings immediately

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

    J.   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.

    K.   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 tarps, enclosure on
         scaffolding).

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 cleaning agents.

                        END OF SECTION
 


mortar joints, joints, cracks, mortar, mortar type, granite