Repointing Marble

Procedure code:
445520S
Source:
National Capitol Region Specifications
Division:
Masonry
Section:
Marble
Last Modified:
03/03/2017

 

REPOINTING MARBLE

 

PART 1---GENERAL

1.01 SUMMARY

 

A. This procedure includes guidance on raking out and

   repointing the deteriorated or inappropriately repointed

   horizontal and vertical joints on exterior marble.

B. 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

1.03 QUALITY ASSURANCE

 

A. Regulatory Requirements: Marble Design Manual, ASTM C144-

   70, Aggregate for Masonry mortar; ASTM C150-74 Portland

   Cement; manufacturer's printed recommendations for

   product use and installation.

B. Certifications: Prior to delivery, submit certificates

   attesting compliance with applicable specifications for

   grades, types, classes.

C. Field Samples: Prior to raking out all areas, cut back

   joints at location selected by the 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 and

   left unpointed until all other pointing is completed.

   Point when directed by the Contracting Officer.

 

1.04 PROJECT/SITE CONDITIONS

 

A. Existing Conditions: No stone work will be performed when

   the air temperature is 40 F and falling or when stone

   surface temperature is 40 F or below.

 

PART 2---PRODUCTS

2.01 MATERIALS

 

A. Portland cement: Type I, ASTM C150, gray and/or white as

   necessary to match mortar color specified.

B. Hydrated masons lime: ASTM C207.

C. Aggregate: See ASTM C144 (ASTM 1997a). Clean sharp sand free of loam, silt, soluble salts and organic matter.        Sand color should match stone color as closely as possible. Aggregate shall conform to the size gradations             specified as a result of laboratory analysis of an approved sample.

   1. Choose the color of the aggregate so that the dry

       mortar color matches specified color.

D. Water: Clean and free of deleterious amounts of oils,

   acids, alkalis and organic matter.

2.03 EQUIPMENT

A. Chisels

B. Joint tools

C. Hawks

D. Stiff fiber bristle brushes

E. Trowels

F. Rubber mallet 

2.04 MIXES

 

A. Proportions for Marble Pointing, or as determined by

   mortar analysis:

   1. Portland cement: 1 part by volume

   2. Lime: 2 parts by volume

   3. Aggregate: 9 parts by volume

   4. Water: To form a workable consistency

 

B Mixing Procedures:

 

   1. Measure materials by volume or equivalent height.

   2. Do not measure by shovel. Use known measure.

   3. Mix ingredients in clean mechanical batch mixer for 3-5 minutes.

   4. Let mortar sit for 20 minutes prior to use to allow

       for initial shrinkage. Use mortar within 1 hour

       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 more than width of the mortar joint. 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 marble. 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.

B. Raked joint depth to be at least 3/4" but in all cases rake

   back to expose sound mortar. Raked joint depth should be 2 to 2 1/2 times the joint width.

C. Brush, vacuum or flush joints to remove all dirt and

   loose debris.

D. Reduce initial absorption of the stone by thoroughly

   wetting (surface dry) with clean water just prior to

   repointing.

E. 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.

F. Use clean tools and equipment free from hardened or

   partially set mortar.

G. Clean excess mortar from stone and joints, removing

   splashed mortar and droppings immediately.

H. Do not retemper or use mortar which has partially set, is

   caked or is lumpy.

I. Finish horizontal and vertical face joints. Do not allow

   mortar to extend over the surface of the stone.

   J. 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 repairing, pointing and resetting the

   marble, immediately remove mortar, grout and adhesives

   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 marble only with fiber bristle brushes and water.

   Use no acids, detergents, or other cleaning agents.

 

END OF SECTION

 

Last Reviewed 2017-03-03