The on-site personnel should be familiar with the applicable sections of the Project Specification pertaining to delivery, storage, setting, patching, cleaning, pointing, caulking and sealing.

The following checklist has been developed for Cast Stone installations.

1. Prior to delivery there should be a set of the approved shop drawings and the approved color and texture sample on file. All test reports specified should be submitted as required.

2. Upon delivery, all Cast Stone should be checked for chips, cracks, stains, or broken pieces. Any damage should be noted on the delivery slips and communicated to the manufacturer or the sales representative.

3. Color and texture should be inspected in accordance to approved color sample or mock-up 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 approved sample when viewed in good typical daylight conditions at a ten foot distance. (See technical literature on Inspection and Acceptance.)

4. Storage of Cast Stone should be above the 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. Allow for air circulation.

5. Prior to setting, insure climatic conditions are within thermal limitations of mortar. Mortar retarders and accelerators should be used according to manufacturer’s directions but not with patching material. Set stone in full mortar joints and fill all dowel holes and anchor slots completely with mortar. Insure uniform joint widths within specifications tolerances.

6. Ensure that all specified flashing and damp-proofing is installed. Flashing pierced by stone anchors must be sealed either by metal thimble, grommet or approved sealant.

7. Concrete should never be poured against unprotected Cast Stone. Where poured in place concrete is placed against Cast Stone sills, separate with appropriate material prior to pouring concrete.

8. Stone anchors must meet specified standards and be non-corrosive. Stone slots to receive anchors should be completely filled with mortar.

9. Prior to setting insure that the surfaces set in mortar are drenched with water. This will ensure a good bond and help to prevent mortar shrinkage.

10. Weep 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.

11. All head joints at coping and joints at column covers, soffits, and, in general, all stone sections with projecting profiles, exposed top joints or rigid suspension connections to the supporting structure should be sealant joints. After stetting, prime the ends of the stones, insert properly sized backup rod and gun in sealant.

12. All trim items except parapet coping must align with control joints. Do not bridge coping over expansion joints.

13. Cast Stone should be handled to minimize chipping. Care must be taken not to bump the stone into anything. Handle stones with the wide portion of the cross section in the vertical position to minimize breakage.

14. After setting, columns, pilasters, entry jambs, window sills and all stone with projecting profiles should be protected during the remaining construction.

15. During construction, cover open walls when rain is anticipated.

16. Chipped Cast Stone must be patched by skilled mechanics. A trial patch must be approved before general patching is to commence.

17. Planter coping, fountain coping, swimming pool coping, treads, risers, stone pieces at grade, and pavers should be treated with a silane or siloxane water repellent after setting. This will minimize the likelihood of dirt and groundwater entering the surface of the stone; a frequent cause of staining, efflorescence and enhancement of crazing. Check that water repellent does not affect color or texture when dry.

18. Load bearing units should be reinforced as necessary. They may not be designed to be handled in a different orientation than they will be installed in the structure. Lintels and large panels must be kept vertical.

PATCHING
The best insurance against chipped stone is care in handling and protection of the unit after installation. Even with all of the special care and protection, building stone still becomes chipped from time to time and a certain amount of patching is to be expected.
Any chip obvious from a 20' distance should be patched. Chips measuring 1/4" and less across the face should not be patched and are usually left alone. Stone units with chips larger than 1" square should be replaced, unless the damaged portion can be salvaged and expoxied back to the unit. Most cracks can be patched if the units are reinforced.

Climatic conditions must be taken into consideration before patching is to commence. Do not patch stone in freezing weather or if a freeze is anticipated within 24 hours. On hot sunny days patching should be done during the morning hours where the Cast Stone is shaded or at temperatures less than 90 degrees Fahrenheit. Patches should be covered with a damp cloth and plastic sheet to prevent the cement from hydrating too quickly. The stone that is to receive the patch should be wet down with clean, cool water until it will not absorb any more moisture. This process is necessary to stop the dry stone from absorbing the moisture in the patching material. Without moisture retained in the patching material, it would dry out before curing and flake away from the stone.

The same material that was used to manufacture the Cast Stone should be used for patching. Experimental batches should not be used in an effort to obtain an instant color match. The water/cement ration used should be as close as possible to the mix at the time of manufacture. Acrylic latex bonding agents may be used, but not in place of water. Use as a wetting agent; less than a tablespoon per handful of patching material. Never use metal tools for applying a patch. Stones which were acid etched at the factory will require the same treatment applied to the patch.

A properly executed patch will not match in color immediately. Dry cast products will appear lighter where repaired; wet cast products may appear darker. Patches that match immediately or in two or three days have a tendency to change color later on after a period of weathering. Through curing, weathering and ultraviolet light, the patch will eventually return to the original stone color. This process could take 3 months to a year or longer depending on the climatic conditions and exposure to the weather.

Patches which cannot be seen from a 20' distance when viewed in good typical lighting should be accepted.

CLEANING
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. Varieties 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 on.

Whenever possible, the mason should protect the cast stone during installa tion from mortar stains and scratches until all masonry work above the stone is completed. The most common stains during construction are due to dirt and mortar. Dirt can be removed by scrubbing with a mild detergent and water. Mortar stains require cleaning with a hydrochloric based masonry detergent. The best way to avoid stains is to protect the stone with plastic until the wall has been cleaned.

Cast stone, like brick, is subject to vanadium and other metallic stains. DO NOT use muriatic acid on cast stone as it can burn and/or stain, as well as leach organic and inorganic particles to the surface of the stone. If cleaning is required, we suggest only using products such as “Diedrich 202V”1 or “Sure Klean 600 Detergent or Sure Klean Vana Trol”2 and follow the manufacturer’s recommendations on dilution.

Consult the brick supplier prior to applying acids to trim items. Insure that lower stone courses to be cleaned are frequently drenched with water because as acid is rinsed down the wall it can gather strength when reapplied. Take neces sary steps to protect window, door and grade materials. Pre-soak the stone thoroughly with water. Apply properly diluted masonry detergent with either a dense, soft masonry brush or low pressure (40-50 p.s.i.) airless sprayer of a corrosive/acid resistant type (do not use metal or wire brushes). Dwell time on the stone should be about 5 minutes.

Allowing the detergent to dry on the surface may result in stains and residue. Using fresh water, thoroughly rinse the stone’s surface to remove any chemical residue or free sand immediately after cleaning and before it is allowed to dry.

When unusual stains are encountered, the same procedures which are recommended to clean concrete will 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 it’s cause. There are degreasers and paint removers readily available. Any treatment should be tested on a small inconspicuous place prior to cleaning the visible areas of the unit.
A sealant on cast stone is not normally necessary or recommended, as some types of sealers inhibit the natural absorption and evaporation of moisture.

1 “Diedrich 202V” is a product of
Diedrich Technologies
7373 S. 6th Street
Oak Creek, WI 53154
phone: 1-800-323-3565
Web Site: www.execpc.com

2 “Sure Klean 600 Detergent” and “Sure Klean Vana Trol” are products of
ProSoCo, Inc.
P.O. Box 171677
Kansas City, KS 66117
phone: 1-800-255-4255
Web Site: www.prosoco.com

NOTE: The stronger the solution, and/or the longer the solution is allowed to set on the surface of the stone, the rougher the finish of the stone will become.

COLD WEATHER SETTING PRACTICES
Never set Cast Stone on a frozen or ice covered wall. All masonry bond will be ineffectual. Cold weather building practices have been developed to protect masonry against the perils of freezing when construction must be carried on in such environments.
Avoid setting stone with mortar in extreme cold. Stonework set in cold (below 40 degree) weather may expand and crack mortar bond in warm temperatures. Calcium chloride will cause efflorescence. Mixing water may be heated up to 160 degrees to heat the mortar to between 40F and 120F. Sands may be heated with propane or air blast heaters. All materials must be heated slowly to prevent scorching.

The International Masonry Industry All Weather Council recommends the following:

Above 40F: Normal masonry procedure. Cover walls at end of workday to prevent water entering masonry.

40F - 32F: Heat mixing water to produce mortar temperatures between 40F - 120F. Cover walls with plastic or canvas to prevent wetting and freezing.

32F - 25F: Heat mixing water and sand to produce mortar temperatures between 40F - 120F. Cover walls with plastic or canvas to prevent wetting and freezing.

25F - 20F: Heating mixing water and sand to produce mortar temperatures between 40F - 120F. Cover walls with plastic or canvas to prevent wetting and freezing. Mortar on boards should be maintained above 40F. Cover walls and materials at the end of the day to prevent wetting and freezing. Maintain masonry above freezing for 16 hours using auxiliary heat or insulated blankets.

20F - 0F: Heat mixing water and sand to produce mortar temperatures between 40F - 120F. Cover walls with plastic or canvas to prevent wetting or freezing. Mortar on boards should be maintained

above 40F. Cover walls and materials at the end of the day to prevent wetting and freezing. Provide enclosures and supply sufficient heat to maintain masonry enclosure above 32F for 24 hours.
Patching should not be done in any environment which may be subject to freezing within 72 hours.

MORTARS
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, be durable, resist rain penetration as much as possible and yet be flexible enough to accommodate slight movement within the wall.

Mortars 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 used.

The 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 joint shrinkage.

Although 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 specific applications.

Proper mixing is essential to good consistency. All materials are measured by volume. Sands should be 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 discarded.

Head 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 wall below.

Only the ends of the lug window sills and stair treads should be set in mortar. This prevents the stone from cracking due to loading and future settlement.

Rake 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. Sponge all mortar smears from face of stone with water. Hardened, smeared mortar is difficult to remove from the surface of cast stone.

The 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.

SEALANTS
The 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 at 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 be "soft" sealant joints.

Mortar 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 and point mortar joints rather than full-bed setting and finishing in one operation.
Sealant joints allow for movement at the vertical joints. Leave head joints dry when setting. It is a mistake to use mortar in combination with sealant in the same joint. An allowance for compression is required for the system to be effective. After setting, prime the ends of the stones, insert properly sized foam backup rod and gun in sealant.

Since sealant systems are not intended to bear weight, use plastic setting pads or lead shims when setting the stones on a soft bed joint. The sealant is not intended to adhere to the foam backer rod. The sealant should adhere to the parallel surfaces only. The foam rod should be placed to a depth approximately equal to the width of the joint.

Sealants are specified under section 07920. The most common types are one-part "moisture cure" or "air cure." Two part systems are also available which require the mixing of materials together to allow chemically induced curing.

The inherent properties of silicone products make them excellent sealant materials. Silicones provide superior weathering resistance and perform over a 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 flexible and durable.

Two component polyurethane sealants are tough and elastic, allowing for movement of up to 50% of the joint width. They are also durable, flexible and form a watertight bond with most building materials. According to the manufacturers, these formulations offer weather-tight seals in caulking joints today for as long as 20 years under normal application conditions and ten years under severe conditions.

Allowance for thermal and other movement should be within 25% of the joint size. For instance, a normal 3/8" joint should be expected to compress to approximately 1/4" and expand to approximately 1/2" during elongation.

POINTING OF JOINTS
Always rake and point mortar joints rather than full-bed setting and finishing in one operation. Mortar 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.

Not all joints between stones or between stone and other material should be filled with mortar. All head joints at coping stones and joints at 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 be "soft" sealant joints.

Pointing is required because mortar shrinks and settles as it cures. Since mortar beds harden from the face in, stresses can be applied to the edge of the stone which can cause spalling later. Shrinkage also 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 must be raked out of the joint to a minimum depth of 3/4". If sealant is to be used at the head joints, then mortar should not be used there at all.

Pointing is usually done in 1 or 2 stages to allow maximum sealing of shrinkage cracking in the mortar. It should not be done in areas exposed to hot sunshine and it is suggested that pointing be accomplished after patching of Cast Stone and before final wash-down.

Apply pointing mortar using proper tools to compress the material against the edges of the stone. A concave joint is recommended for the best protection against leakage although other joint types are often available in the stone setting trade.

Pointing mortar should be softer than the stone so 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:

1 part Portland cement, ASTM C150
1 part hydrated lime, ASTM C207
6 parts masonry sand, ASTM C144

Coloring 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 away from the 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 must not exceed 10% of the weight of the cement used. Carbon black or urtramarine blue pigments should not be used. In general, pigmentation types and amounts used in the manufacture of Cast Stone can also be used as a starting point when custom blending the pointing mortar to match or complement the color of the Cast Stone.

Always 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.

DESIGN TIPS
Improvements in the availability and economy of Cast Stone can often be achieved when the specifier balances the needs of a project with the degree of custom shapes needed for the cast stone installation. The indirect labor costs of design, layout, supervision, coordination and mold making required for a “full custom” project can greatly exceed the actual direct cost of just casting and delivering a basic or standard product to the jobsite. This causes wide variances in the price of Cast Stone and places a premium on the product, which is not always necessary.

With the foregoing in mind, Cast Stone projects will generally fit into one of the following categories: Standard, Semi-Custom or Custom:

Standard Cast Stone items are purchased according to a manufacturers catalog, shop drawing or inventory of moulds. They may be ready made items or made to order. The units are usually priced individually. The architect or contractor determines the quantities and location of each unit on the structure as well as the method of anchoring to the structure, if required. The Cast Stone manufacturer provides no layout drawings. Cutting of units in the field is usually required.
Semi-custom Cast Stone items are purchased according to unit shapes shown on contract documents or according to shop tickets specially prepared to define the scope of the work. They are usually made to order either from custom or inventoried moulds. The units may be priced either individually or as a lump sum contract for the project. The Cast Stone manufacturer prepares shop tickets for approval, which show the quantities, cross section, reinforcement, finished faces, anchoring provisions and a schedule of lengths to be provided. The architect or contractor confirms the quantities, sizes and location of each unit on the structure as well as the method of anchoring to the structure, if required. The Cast Stone manufacturer provides no layout drawings. Some cutting of units in the field may be required.

Custom Cast Stone items are purchased strictly according to contract documents and according to shop drawings specially prepared to confirm the scope of the work. They are usually made to order from custom moulds. The units are usually priced as a lump sum contract for the project, according to plans and specifications. The Cast Stone manufacturer prepares shop drawings for approval, which show the details of stones, arrangement of joints, quantities, cross section, reinforcement, finished faces, anchoring methods, anchors and the location of the units on the structure. The architect and contractor approve the shop drawings to confirm the Cast Stone manufacturers interpretation of the contract documents, quantities, sizes, location of each unit on the structure, method of anchoring to the structure and coordinate the interface of the Cast Stone with other trades. The Cast Stone manufacturer normally provides layout drawings. Cutting of units in the field is usually not required.

In many specifications today, architects are requiring layout drawings that call for the location of every joint on the building façade to be precisely located, while others desire standard products and consider custom products to be cost prohibitive. Methods are available for controlling joint locations when using semi-custom typical lengths and standard products as described herein and they should be used whenever possible.

Where jointing layouts are not clearly shown on contract documents or where shop drawing requirements are not clearly spelled out in the project specifications, misunderstandings and disappointment can develop between the architect and Cast Stone manufacturer, unless the parties first agree that the job will be fully custom in nature.

When the architect implements a standard or semi-custom design, which commits to a certain number of shapes and sizes, the approval process is significantly streamlined and delivery times are shortened. The masonry contractor may choose to receive a neat pallet of modular units, which can easily be cut to fit the exact as-built dimensions at the jobsite.

For most installations, typical lengths will be the common unit, with 4’-0” modules (3’-11 5/8”) as the most popular size. Longer lengths are available but should generally not exceed 15 times the minimum cross section thickness. Control joint spacing should divide evenly by the size of the typical unit. Special corner and end units should be cast to suit the end-of-wall condition and intermediate units may be cut with a standard abrasive blade masonry saw.

A typical fitting specification should include the following:

1. Follow architect’s jointing pattern as shown on contract drawings.
2. Cut units to suit in-place wall dimensions.
3. All window and door surrounds shall consist of evenly sized units.
4. Apply zinc primer to all exposed reinforcement before setting stone.

Window sills should be sized to fit the masonry opening or mullion spacing, with allowance for 3/8” joints. The height of all Cast Stone, which is built into masonry walls, should match the brick coursing. Profiles should be designed with the Cast Stone Institute Value Engineering suggestions at hand.

Standard Cast Stone jobs are best suited for designs that call for basic and popular items such as band courses and wall cap coping, pier caps, keystones, quoins and window sill units sized to replace brick. Semi-custom projects can include almost any application where the designer is willing to dimension the stone units on the contract documents.

Custom Cast Stone designs represent the majority of buildings under construction today. Layout drawings are needed for projects that have many different profiles running through changing wall sections or one-of a-kind installations such as entrances, porticos and signs. Base courses of stone at changing grade elevations, radius walls and applications suspended from structural concrete or steel are other good applications for custom Cast Stone.

FLASHING AND WEEP HOLES
Proper flashing and weep holes are essential elements in exterior masonry walls. Together, they provide a means to control moisture in a wall. If not addressed, moisture can have damaging effects on exterior walls. Excessive moisture within masonry can lead to crazing, efflorescence and spalling in some cases. Improper flashing can lead to moisture in the interior of a building. An effective system to deal with exterior moisture penetration is necessary for a properly functioning Cast Stone wall.

A drainage wall, also known as a cavity wall, is the most effective solution for a Cast Stone wall exposed to the elements.

THE DRAINAGE WALL
A drainage wall has five essential elements.
• Exterior wythe of masonry
• A clear cavity, or air space, of at least 1 inch
• An interior wythe of masonry or other backing material
• Flashing at all interruptions in the drainage cavity
•Weep holes at all flashing locations. Recommended spacing of 24 in. o.c.

The exterior wythe provides first resistance against moisture penetration. Cast Stone should be laid with full joints in mortar meeting the requirements of ASTM C 270, Type N mortar. Care should be taken when laying the stone to ensure the cavity behind this wythe stays clear. A tapered bed joint can help minimize mortar droppings and protrusions into the drainage cavity.

A minimum 1 in. cavity or air space is recommended. Cavities of 2 in. or more are easier to keep clear of mortar and debris. Cavities over 4 in. may require special ties and anchors. When insulation is specified, the clear space of the cavity is measured from the outer face of the insulation to the back of the exterior wythe.

Through-wall flashing and weep holes should be used at the base of the drainage wall and at all interruptions in the cavity, such as at window heads and relieving angles. Flashing must be continuous and properly lapped and sealed at the base of the wall and at relieving angles. When flashing is used over openings, such as at windows, end dams are required.

Weep holes direct water from the drainage cavity to the outside. Open head joints of at least 1 in. in height are recommended. Open weep hole joints provide the best drainage. They should be spaced no more than 24 in. apart. Rope wicks can also be used, but weep holes should be placed closer together, at 16 in. o.c., since this type does not drain as quickly. Plastic tubes are not recommended because they are easily clogged by mortar or by insects. In stones over 24 in. in length, a 3/8 in. wide by 1 in. high notch through the base of the stone is recommended for drainage. Unnecessarily long lengths of stone are discouraged because adequate drainage between weep holes can be a problem. Moisture retained in the wall can lead to crazing of the Cast Stone.

FLASHING AT BASES
Flashing and weep holes must be used at the base of a cavity (drainage) wall and at all relieving angles. Flashing should extend from the exterior face of the Cast Stone wythe into the cavity. In the case of a masonry backing wythe, the flashing should be turned up a minimum of 8 in. and extend into the masonry backing. In framed backing walls, the flashing should extend up the cavity at least 8 in. and be attached to the exterior sheathing. Building paper or other water resistant membrane on the interior wythe should overlap the top of the flashing.

Flashing is also recommended below all Cast Stone belt courses and watertables that sit on a relieving angle or occur at a change in material, i.e. stone to brick. In most cases, flashing and weep holes should be placed directly below the Cast Stone course for proper drainage of the cavity. In cases where stone and clay brick are used together in the same wythe, the flashing also serves as a bond break between the Cast Stone and the brick. Because clay brick undergoes irreversible moisture expansion and Cast Stone, like other cementitious products, tends to shrink, flashing between the different courses allows horizontal movement to occur without cracking the mortar joints or units. The Brick Industry’s Association Technical Notes 18 Series provides further information on this topic. Stones must be anchored, top and bottom, to the backing material when this detail is used.

FLASHING OVER OPENINGS
Cast Stone window heads and arched openings also require flashing. If the Cast Stone is supported by a relieving angle, flashing and weep holes are located below the stone course, on the relieving angle. When no relieving angle is used, as in the case of structural stone lintels, flashing should be placed directly above the stone course. In either case, proper anchorage of the stone to the backing is imperative.

FLASHING AT COPINGS AND CAPS
Experience has shown that Cast Stone copings perform best when the mortar bond with the masonry wall is maintained. For this reason, flashing should not extend over the full width below the Cast Stone coping. Instead, the flashing should be turned down into the drainage cavity and then out through the exterior supporting wythe below. This differs from recommendations found in the Brick Industry Association’s technical notes.

At chimney caps, step flashing from below the Cast Stone coping down through the first course of supporting masonry below the cap. Weep holes should be located in the head joints of the first course of supporting masonry.

ANCHOR PENETRATIONS THROUGH FLASHING
The anchors for attaching Cast Stone may be required to penetrate flashing and building paper to allow a secure connection to the structure. Where this occurs, proper steps must be taken to ensure a watertight connection at the interface so that the anchor does not compromise the integrity of the flashing. Grommets, thimbles, sleeves, couplings and sealants are available for this purpose, but it is beyond the scope of this Technical Bulletin to provide specific guidance.

FLASHING MATERIALS
Flashing is a key element in a drainage wall. Poor flashing materials can become brittle over time and may allow water to penetrate the building interior. As a result, longevity and life cycle cost should be considered, in addition to first costs, when choosing a flashing material.

Flashing materials used successfully with Cast Stone include stainless steel, copper, copper laminates, EPDM, and rubberized asphalt. Polyvinyl chloride (PVC) and galvanized steel flashing should be avoided because of their questionable long-term performance. (See the Brick Industry Association’s Engineering & Research Digest, "Through-Wall Flashing", for a detailed discussion.) Table 1 lists some advantages and disadvantages of each of the recommended flashing materials that must be considered in making a final selection.

WATER REPELLANTS
The technology of waterproofing masonry materials has improved considerably in the last few years and many durable water repellent materials are available which can reduce water intrusion through brick, stone and mortar joints. Proper application of waterproofing materials can be a long lasting minimizer of efflorescence, mildew, staining and dirt. Many materials are offered with 5-10 year warranties. Some studies indicate that water repellents can reduce freeze-thaw damage to masonry products and prevent loss of insulation value.

The most popular and time-tested water repellents include silicones, acrylics, silanes and siloxanes. Silicones are relatively inexpensive, only provide a surface film, and usually, only last a short time. Silicones are mainly used to keep Cast Stone clean during construction operations and they make the finished installation easy to clean. Many types of acrylics are available but most have poor vapor transmission, low penetration and inadequate resistance to ultraviolet light. Some acrylics have been known to turn yellow or produce gloss. The Cast Stone Institute recommends the use of silane or siloxane (or blends containing each) for weatherproofing Cast Stone when a water repellent is desired.

Silanes and siloxanes work by penetrating the exterior surface and then undergoing a chemical reaction with the moisture to form a water-repellent silicone resin within the void structure of the Cast Stone. Since they react with water, walls may be slightly damp but if water is contained in the pores, penetration may be limited. Do not apply the product within two days of rainfall or building washdown. Air temperature should be at least 50F for most materials and not below 40F for 24 hours. The application must be dry before the wall is allowed to get wet.

Water repellents are not a remedy for water absorption problems which are caused by poor details such as the improper use of flashing, lack of weep holes, non-ventilated wythe, failure of joint materials or the use of hard mortar joints where sealant joints should be used. Cast Stone has a natural permeability which is approximately equal to natural limestone and architectural concrete. The purpose of a water repellent should be to prevent water intrusion through the outer surface of the brick, mortar or Cast Stone, while allowing sufficient vapor transmission to let moisture out of the wall cavity, thereby improving weathering qualities and the ability to easily clean the surface if it becomes dirty.

Proper evaluation of suggested water repellents should include inspection of similar installations where the proposed material has been used under similar exposure conditions. The application should be guaranteed by the manufacturer or the applicator not to discolor the Cast Stone. Water repellents should be applied after all pointing, patching, cleaning and inspection operations are completed.