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TECHNICAL BULLETIN—BEFORE YOU BEGIN

 

The following is a guideline for procedures and precautions that should be considered before the installation of cast stone. It is provided for informational purposes. Consult your architect or designer, and your manufacturer for additional information.

 

All on-site personnel should be familiar with all project specifications related to all aspects of the job, including packaging, delivery, storage, installation, anchoring, patching and repair, cleaning and sealing. If the project specifications are not specific in any area, the industry standards should be followed.

 

Cast stone is an architecturally designed and molded masonry material that is available for decorative purposes, and not load bearing purposes. It is well suited for full veneer wall facings, columns, balustrades, coping, trim, banding, fireplaces, window sills, and surrounds, door surrounds, and decorative medallions strategically placed around any building or structure. It provides color, contrast, decoration, and elegance to any project.

 

Cast stone material is designed for both indoor and outdoor purposes. Once it is cured, it is very strong and based upon design and shape has an internal reinforcement giving it added strength.

 

After the order is placed and before the delivery of material, job personnel in charge of the project should be familiar with the cast stone material specifications and installation requirements.

 

All approved shop drawings and a set of setting plans should be available to the job superintendent, inspector, contractor, and mason, so they can make themselves familiar with the up and coming material. Review will allow them to strategically plan the installation of the material as well as direct the storage of the cast stone material when it arrives.

 

Since there are setting plans on-site, it is easy to match the bills-of-lading to the required material list to ensure that all material has properly arrived on-site. Verifying the material count on the pallets and confirming that all pallets have arrived is essential. Any missing material, cracked, chipped, broken, or damaged material should be reported to the manufacturing plant. Small chips of less than a quarter inch cannot be seen at a distance of ten feet, can be patched if desired, but may not be grounds for rejection of material.

 

Color samples should be available to the job superintendent or inspector so they can match the cast stone to the sample. Note that samples that have been sitting in an indoor facility for a while have dried out and are probably lighter in color than the material that is received. Wet material is darker than dry material and can take up to six months to blend with the color sample. Wet material may be blotchy looking, but this in no way affects the integrity of the cast stone. Drying and time will blend the blotchy affect to a consistent color.

 

Texture of the stone should be inspected. Keep in mind that cast stone may or might not have been acid washed before shipment. Color samples are generally not acid washed and cleaned before sending out. Once all material has been installed and inspected, it should be properly cleaned then sealed with water repellent. The texture of the cast stone material should appear the same at a distance of ten feet thereafter.

 

Crazing (spider web cracking design) and efflorescence (white crystalline, shiny appearance) on the cast stone are not grounds for rejection. Washing the material with a mild acid mixture, or soap and water should remove the effects. Note that the solution that you use can bring additional chemicals to the surface that can enhance the effect, thus the stone may require a couple of washings to eliminate such effect. Keeping any material that has a crazed appearance out of the dust and dirt environment will help eliminate any dirt settling into the minute cracks.  Please see the appropriate bulletins on crazing and efflorescence for further information.

 

Preparation for storage of the material is important. The material must be stored on non-staining pallets or materials, away from as much dust, dirt, oils, and paints as possible, and stored with proper air circulation. Making sure that the material is not stored in a heavy traffic area protects it from possible chipping and breakage because of bumping, flying debris from passing vehicles and the like.

 

Ensure that weather conditions have been considered before installation. When rain is in the forecast, take precautions to cover open areas and insure proper drainage of water. Confirm that no standing water sits around the cast stone material.

 

Mortar, chalking and grout should not be applied in weather less than 46°F, 60°F, or more is best. In hotter climates, it is best to install in early hours when the weather is cooler and in areas that are shaded. Placing damp cloths and plastic over materials, keeping them well moistened, especially patched areas, helps prevent the material from drying too rapidly. It is important to keep in mind that any mortar or grout that is used should also be keep moist to eliminate quick drying and shrinkage. Mortar that is over 90 minutes old should generally be discarded.

 

Ensure that all mortar joints, dowel holes, and anchor slots are properly prepared and ready to be filled. Ensure that the material is aligned properly and you are prepared with spacers so material is evenly spaced. Improper preparation and installation will lead to disappointment of the finished project.

 

Confirm that you have examined the proper use of anchors and supports for the masonry materials used. Cast stone material should have been designed so no lip is less than three-quarter, minimum one inches best, to prevent cracking or chipping of material should it be hit.

 

Keep in mind that movement is possible throughout the years. It is important to make sure that you make yourself familiar with the different movement, expansion, and contraction of all masonry materials that will be used. Proper use of sealants should be considered for the different joints in columns, coping, banding, soffits, any projecting profiles, top joints, rigid suspension connections, and the like, to prevent cracking and shifting of materials. After initial installation, the joints should be properly primed and sealed. When combining the different masonry materials, including cement, take precautions to use any separation, and masking off material---painters tape is an excellent method---required by the specifications and masonry standards.

 

Once material with projecting profiles has been installed, it is extremely important to ensure the protection of the material. Window and door surrounds, sills, coping, banding, water tables, columns, capitols, and the like, all have some type of decorative profiles that need to be protected as the rest of the structure is constructed.

 

Basic construction practices and industry standards should be followed throughout the project. Ensure proper installation of weep holes over windows, at relieving angles, and at the bottom of walls. It is important that no mortar drip in the wythe between the face of the structure and the back of the stone.

 

If material has chipped during installation, it can be patched using the same materials that the cast stone was manufactured with. Patch kits are available and are usually shipped with the original order. Patch kits contain three parts sand to one part cement, plus any pigment as necessary. Adding enough water to the mix to make it pliable but not too wet is important. You may want to verify that you have the patch kit material ready at the start as you do not want to wait for it to be shipped from the manufacturer. Additionally, should time elapse, sands do change slightly over time in color and in aggregate size, therefore, the new patching material may be slightly off in color and consistency. Usually, this is not noticeable but something to keep in mind at the start.

 

A white acrylic bonding agent can be purchased at any home improvement center and used in the patch kit mix (one tablespoon bonding agent to one handful of mix). You may wish to test the color of the mix when using the bonding agent as it can tend to whiten the patch kit material.

 

Instead of adding the bonding agent directly to the mix, you can spread the bonding agent over the chipped area making sure it is not too close to the edge of the chip and then apply the patch material.

 

If you do not have any patch kit material available, you can finely grind up a cracked or unused piece of stone to make your own matching color patch material. Leaving just a little bit extra on the patched piece and let it dry for a short while will allow you to brush it with a rough clean cloth, carpet, or a soft brush to easily blend it with the cast stone and mortar.

 

Use wooden or plastic tools, not metal, to finish the patching. If the weather is hot, cover the patch with a damp cloth and plastic so it does not dry too fast. Spraying the area that requires patching first with water helps with the bonding of the patch material. Keep the spray bottle handy for additional moistening of the damp cloth throughout hotter days.

 

Once all the material has been installed, inspected, and final approval has been given, sealing the cast stone material with a water repellent is suggested. Material used around areas that will see a lot of water like planters, fountains, pool copings, water tables, and wall copings that will receive frequent watering by sprinklers, should especially be treated. Be sure to protect the other areas of the building such as doors and windows when applying. See the Bulletin for Water Repellents for suggestions on the best solutions to use.

 

Note that careful planning at the start will assist in eliminating disappointment for any homeowner or commercial designer at the completion of the project. Careful quality assurance and control of the cast stone material on-site are important as chipping and cracking will occur if the cast stone is not properly handled. Ongoing inspection at the job site will keep all parties informed of the expectations and progress of the project.

 

There is so little one can do to change the appearance of cast stone after installation, therefore, we strongly suggest that careful consideration and planning are executed from the start.

 

TECHNICAL BULLETINS —BEFORE YOU BEGIN (PDF)

 

The information within this and all our bulletins has been provided as a guideline and based upon statistical data and prior uses. We always suggest that you consult with your engineer, architect or contractor for the best design and use of cast stone for your project. Our design team is always available to answer any of your questions. We do not accept any liability from damages resulting from your interpretation of the data contained within.