construction, prevention against staining is
mandatory and becomes the best solution for a clean
finished project. Every effort should be taken to
protect the Cast Stone during storage, setting, and
after installation. Storage of Cast Stone should be
above ground on non-staining planks or pallets. The
storage site should be away from heavy construction
traffic. Cast Stone stored for an extended period of
time should be kept on pallets or non-staining
planking and covered with non-staining tarpaulins.
After setting, columns, pilasters, entry jambs,
windowsills and all stone with projecting profiles
should be protected with non-staining materials
during the remaining construction.
Regardless of the degree of care exercised
during construction, a final washdown will be needed
and, normally, whatever
is specified to clean the
brickwork will adequately clean the Cast Stone. A
variety of commercial cleaners are available and most
contain detergents combined with mild solutions of
phosphoric and/or muriatic acids. Extreme care
should be taken when applying acidic cleaners to
areas where joints are left open or where sealant is
used as jointing material. The sealant manufacturer
should be contacted to ascertain compatibility with
cleaning materials. Acids left behind the stone on
masonry wythe may cause corrosion problems later
The most common stains due to construction are dirt
and mortar. Dirt can be removed by scrubbing with a
mild detergent and water. Mortar stains require
brushing a solution of one part hydrochloric acid to
six parts water on the stain. Soak the stone with water
prior to adding any acid solution to prevent surface
burning. Consult the brick supplier prior to applying
acids to trim items. Insure that lower stone courses
are frequently drenched with water because as acid
is rinsed down the wall it can gather strength when
reapplied. Take necessary steps to protect windows,
door and grade materials.
When unusual stains are encountered, the same
procedures, which are recommended to clean
concrete, will normally clean Cast Stone. The
Portland Cement Association publishes a guide for
the removal of stains in concrete. The most important
step to stain removal is identifying the stain and
its cause. There are degreasers and paint removers readily
available. Any treatment should be tested on a small
inconspicuous area prior to cleaning the main
Dunnage materials used in the packing and transport
of Cast Stone can leave stains (or clean spots) after
becoming wet. Wood packaging products can transfer
resins to the surface, which may be easily removed.
However, solid dunnage made from fresh timber can
cause dunnage marks, which become difficult to
remove. Packing and dunnage materials should
always allow the exposed surfaces to breathe,
especially when stones are palletized or placed into
storage shortly after manufacture. This will avoid
color differential due to moisture becoming trapped
on the surface of the stone.
Power washing and sandblasting
are not recommended procedures for cleaning Cast Stone.
Metal fiber brushes are not to be used for scrubbing
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on-site personnel should be familiar with the
applicable sections of the Cast Stone Institute® Specifications
and the Project Specification pertaining to delivery,
storage, setting, patching,
cleaning, pointing, caulking and sealing. In case
conflict between the two specifications, the Project
Specification should prevail. Where the Project
Specification may not include a particular issue,
the Industry Standards should be followed.
The following checklist has been developed for
to delivery there should be a set of the
approved shop drawings and the approved color
and texture sample on file. All test reports
should be submitted as required.
delivery, all Cast Stone should be checked
for chips, cracks, stains, or broken pieces.
damage should be noted on the delivery
communicated to the manufacturer or the
and texture should be inspected in
accordance to approved color sample
panel set up at the job site. In general,
the color and
texture of the Cast Stone delivered
to the job site
should be approximately equal to the
sample when viewed in good typical
conditions at a ten foot distance.
literature on Inspection and Acceptance.)
of Cast Stone should be above the ground
on non-staining planks or pallets. The
should be away from heavy construction
Cast Stone stored for an extended period
should be kept on pallets or non-staining
and covered with non-staining tarpaulins.
for air circulation.
to setting, insure climatic conditions are
within thermal limitations of mortar.
and accelerators should be used according
manufacturer’s directions but not with patching
material. Set stone in full mortar
joints and fill all
dowel holes and anchor slots completely
mortar. Insure uniform joint widths
that all specified flashing and
dampproofing is installed. Flashing
pierced by stone
anchors must be sealed either by
grommet or approved sealant.
should never be poured against
unprotected Cast Stone. Where poured
concrete is placed against Cast
Stone sills, separate
with appropriate material prior
to pouring concrete.
anchors must meet specified standards and
be non-corrosive. Stone slots
to receive anchors
should be completely filled
to setting insure that the surfaces set in
mortar are drenched with water.
This will secure a
good bond and help to prevent
holes must be installed over windows, at
relieving angles and at the
V bottom of walls. No
mortar drippings shall
be allowed in the wythe
between back of stone and
face of back-up structure.
head joints at coping and sills, and joints at
column covers, soffits,
and, in general, all
sections with projecting
profiles, exposed top
or rigid suspension connections
to the supporting
structure should be sealant
joints. Only the ends
load bearing lug sills
shall be set in a full
mortar to prevent cracking
from future wall
settlement. After setting,
prime the joints, insert
properly sized backup
rod and gun in sealant.
trim items except parapet coping must align
with control joints.
Do not bridge coping
Stone should be handled to minimize chipping.
Care must be taken not to bump
stone into anything.
Handle stones with
portion of the cross
section in the vertical
to minimize breakage.
setting, columns, pilasters,
window sills and
all stone with
should be protected
during the remaining
construction, cover open walls
rain is anticipated.
Cast Stone must be
A trial patch
is to commence.
coping, fountain coping,
of dirt and
of the stone;
- Load bearing units
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Selection of the correct grade of mortar is perhaps the
most important factor in the performance of a
masonry wall. The mortar must have sufficient strength, bedurable,
and resist rain penetration as much as possible and yet be flexible
accommodate slight movement within the wall.
used in the setting of Cast Stone should meet
the requirements of ASTM C270, Type N mortars.
These Portland cement/lime mortars consist of one
part cement (ASTM C150), one part lime (ASTM
C207) and six parts of clean, washed masonry sand
(ASTM C144). They may also contain iron oxide
coloring pigments (ASTM C979) up to 5% of the
weight of the cement when pointing mortars are not
1/1/6 mixture provides good bond strength with
desired weather resistance and moderate compressive
strength relative to the stone when cured. The lime
enhances the workability of the mortar while
reducing shrinkage. The practice of wetting the head
and bed joints of the stone will further protect against
Type N mortar is the standard used in Cast Stone
(as well as many natural cut stone)
applications, the proportions may be varied to suit
mixing is essential to good consistency. All
materials are measured by volume. Sands should
placed in the spiral-blade or paddle type mixer first,
followed by pigments (if required), pre-water, lime
and cement, final water and 5-7 minutes of mixing
time. Mortars unused after 90 minutes should be
joints in most hand set stones may be set with
the usual wet consistency mortar used in setting brick
and block. Stiffer mortar must be used when setting
larger stones and shims are recommended for all
pieces over 300 lbs. When setting, fill all dowel
holes, anchor slots and similar building stone anchor
pockets completely with mortar. Non-shrink grout or
anchoring cement may be specified for dowel
connections. Avoid placing mortar across a full bed
of flashing. The stone needs a bond with the masonry
the ends of the lug windowsills and stair treads
should be set in mortar. This prevents the stone from
cracking due to loading and future settlement.
all stone-to-stone joints to a depth of 3/4”± for
pointing later. Stone-to-brick joints are usually struck
and tooled to a slight concave (See Technical Bulletin
#44 on Pointing). Sponge all mortar
smears from face of stone with water. Hardened, smeared mortar
difficult to remove from the surface of cast stone.
Clean with commercial masonry cleaner such as
SureKleen #600 or Vanitrol with water and a stiff
fiber brush. Consult Cast Stone manufacturer first.
Power washers should not be sued to clean Cast
Stone. (See Technical Bulletin #39 on Cleaning).
decision on whether to use mortar/pointed joints
or sealant joints is a common one. All head joints at
coping and joints at column covers, cornices,
platforms, soffits, and in general, all stone sections
with projecting profiles, exposed top joints or rigid
suspension connections to the supporting structure
should be “soft” sealant joints. After setting,
prime the ends of the stones, insert properly sized backup
rod and gun in sealant (See Technical Bulletin #43 on
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rake and point mortar joints rather than
full-bed setting and finishing in one operation.
Mortar joints are best suited for masonry-bound
items such as belt courses, lintels, window
surrounds, date stones, inscription blocks, quoins,
keystones and similar applications.
all joints between stones or between stone and
other material should be filled with mortar.
joints at coping stones and joints at column
covers, cornices, platforms, soffits, window
general, all stone sections with projecting profiles,
exposed top joints or rigid suspension connections
the supporting structure should be 'soft'
sealant joints (See Technical Bulletin #43 on Sealants).
is required because mortar shrinks and settles
as it cures. Since mortar beds harden
face in, stresses can be applied to the edge
stone, which can cause spalling later. Shrinkage
can create cracks at the joints; a condition
which causes leaking.
Regardless of whether the mortar or sealant
is selected as the face joint material, the mortar
raked out of the joint to a minimum depth of
3/4". If sealant is to be used at the head
mortar should not be used there at all.
is usually done in 1 or 2 stages to allow maximum
sealing of shrinkage cracking
mortar. It should not be done in areas exposed
sunshine and it is suggested that pointing
be accomplished after patching of Cast Stone
before final wash-down.
pointing mortar using proper tools to compress
the material against the edges of
A concave joint is recommended for the
best protection against leakage although other
are often available in the stone setting
mortar should be softer than the stone
that thermal stress will not cause spalling
at the edges
of the joints. It is usually slightly
drier than normal
setting mortar consistency to prevent
shrinkage and is
usually composed of the following:
part Portland cement, ASTM C150
part hydrated lime, ASTM C207
parts masonry sand, ASTM C144
may be added to achieve almost any
hue, however pointing mortar which
sharply contrast the
color of the stone may cause staining.
Excess pointing material must be sponged
face of the stone immediately. Colors
added must be
natural or synthetic mineral oxides,
which meet the
requirements of ASTM C979 (sun-fast,
lime-proof, alkali-resistant) and the dosage
of the weight of the cement used.
Carbon black or
ultramarine blue pigments should
not be used. In general, pigmentation types and
amounts used in
manufacture of Cast Stone can also
as a starting point when custom blending
mortar to match or complement the
of the Cast
specify a mockup wall when approving final colors
and be sure that it has
been properly cleaned
because cleaning will usually affect
the color of
pigmented masonry materials.
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decision on whether to use mortar with pointed
joints or sealant joints between stones is a common
one. All head joints at coping stones and joints
column covers, cornices, platforms, soffits, window
sills and in general, all stone sections with projecting
profiles, exposed top joints or rigid suspension
connections to the supporting structure should
soft” sealant joints.
joints are best suited for masonry-bound trim
items such as belt courses, lintels, window
surrounds, date stones, inscription blocks, quoins,
keystones and similar applications. Always rake
point mortar joints rather than full-bed setting
finishing in one operation (See Technical Bulletin
#44 on Pointing).
joints allow for movement at the vertical joints.
Leave head joints dry when setting. It
mistake to use mortar in combination with sealant
the same joint. An allowance for compression
required for the system to be effective. After
prime the ends of the stones, insert properly
sized foam backup rod and gun in sealant.
sealant systems are not intended to bear weight,
use plastic setting pads or lead shims when
stones on a soft bed joint. The sealant is
to adhere to the foam backer rod. The sealant
should adhere to the parallel surfaces only.
should be placed to a depth
approximately equal to the width of the joint.
are specified under section 07920. The most
common types are one-part “moisture cure” or “air
cure.” Two part systems are also available
require the mixing of materials together to allow
chemically induced curing.
inherent properties of silicone products make
them excellent sealant materials. Silicones
provide superior weathering resistance and perform
wide range of service temperatures. They
are easy to
apply, have low shrinkage rates, and
can accommodate high movement. While organic
materials tend to crack, dry up, and
become brittle or
even revert with age, silicones remain
component, polyurethane sealants are tough and
elastic, allowing for movement of up to 50% of
joint width. They are also durable, flexible
a watertight bond with most building materials.
According to the manufacturers, these formulations
offer weathertight seals in caulking joints today
long as 20 years under normal application conditions
and ten years under severe conditions.
for thermal and other movement should be within
25% of the joint size. For instance,
normal 3/8” joint should be expected to compress
approximately 1/4” and expand to approximately 1/2” during
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