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Historic Preservation - Technical Procedures
Pointing Granite Step Joints
National Capitol Region Specifications - Customs Svc Bldg
Pointing Granite Step Joints
POINTING GRANITE STEP JOINTS
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
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).
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
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
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.
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
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
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.
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
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
4. Let mortar sit for 20 minutes prior to use to allow
for initial shrinkage. Use mortar within 1=AB hours
of initial mixing.
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
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
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
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
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).
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