FAQ

What is cast stone?

Cast stone or reconstructed stone is a concrete masonry product simulating natural-cut stone and is used in architectural applications. ... Cast stone can be made from white and/or grey cements, manufactured or natural sands, crushed stone or natural gravels, and colored with mineral coloring pigments.

Materials and processes used for manufacturing Cast Stone vary according to the aggregates locally available to the manufacturers and the processes and techniques used by the manufacturers to obtain the desired appearance and physical properties. Of paramount importance in molding Cast Stone is the need to use a properly proportioned mixture of white and/or grey cements, manufactured or natural sands, carefully selected crushed stone or well graded natural gravel and mineral coloring pigments to achieve the desired appearance while maintaining durable physical properties.

Although a variety of casting methods are used, production conforming to this standard will exceed minimum requirements for compressive strength and weathering qualities essential for normal installations as a suitable replacement for natural cut limestone, brownstone, sandstone, bluestone, granite, slate, keystone, travertine and other natural building stones. The specifier should not prescribe the casting method.

Definitions

Cast Stone - a refined architectural concrete building unit manufactured to simulate natural cut stone, used in Division 4 masonry applications.

• Dry Cast – manufactured from zero slump concrete.

Vibrant Dry Tamp (VDT) casting method: Vibratory ramming of earth moist, zero-slump concrete against a rigid mold until it is densely compacted.

Machine casting method: Manufactured from earth moist, zero-slump concrete compacted by machinery using vibration and pressure against a mold until it becomes densely consolidated. 

• Wet Cast – Manufactured from measurable slump concrete.

Wet casting method: Manufactured from measurable slump concrete and vibrated into a mold until it becomes densely consolidated. 

• Specifier Note: Slump, manufacturing method, and apparatus shall be selected by the manufacturer and not specified by the purchaser.

Fabrication 

The manufacture of cast stone is the most labor-intensive of all concrete products. Specialized work is usually carried out on a departmental basis consisting of the Drafting/Engineering, Pattern/ Mold, Casting/Curing and Finishing / Shipping areas. Workers develop their various skills in both procedure oriented and craft-oriented ways. The manufacturers have developed procedures that work for the different job functions, but craftsmanship, talent and technique are passed along by the workers, sometimes for generations. 

Planning

To assure the success of the project, the detailer (draftsperson) assigned to a cast stone job must have knowledge of architectural styles and designs as well as experience with the manufacturing techniques and the installation methods. The manufacturer details each piece with an aim toward simplification and standardization. As with any custom product, a great deal of economy is achieved by taking advantage of repetition. Shop drawings should be specified as needed - usually to show details and sizes of stones, arrangement of joints, relationship with adjacent materials and the location of each piece on the structure. 

Some builders and manufacturers, however, prefer to simply work with “shop tickets” which only show the part to be furnished; leaving jointery and fit up to the masonry contractor in the field. 

Cast stone can be formed in a greater variety of shapes than other type of natural cut stone. Lengths should be within 15 times the minimum profile thickness whenever possible. Consult with a structural engineer and/or manufacturer if longer lengths are absolutely necessary. Longer lengths invite cracking and handling problems. Try to keep the backside flat and unexposed to view. Remember, most shapes are cast into a mold with four sides and a bottom. One side will always be unformed; typically the bottom of the stone. 

Never design a piece with a thin projection; one, which has a thickness less than twice the length of the projection. Weight is approximately 135 lbs. per cubic foot. To figure weights per lineal foot simply multiply cross section dimensions in inches. For instance, a window sill measuring 6” high x 10” deep = 60 lbs. per lineal foot. 

(ASC suggested standard dimensions not exceeding a maximum of 36" in length without expansion joint unless otherwise requested by the customer.)

Molds 

The pattern or mold shop is the heart of any cast stone producer’s enterprise. Many cast stone manufacturers have craftsman on staff and/or a CNC machine that is able to produce custom molds. This allows manufacturers the ability to produce almost any stone design element required to fit a project’s needs. 

In general, over 85% of cast stone is produced from new molds but the trend is increasing toward standard inventory availability, especially in the residential and landscape markets. 

In restoration projects, full-length pieces are often salvaged from the original structure and used as models for the actual molds. Ornamental plaster is an excellent modeling material and there are a number of excellent plaster fabricators available for this purpose. One caution though, be sure the materials are not copyrighted.  

Are your products made on site?
Yes, we make the prototype, molds, and cast products at our location.

What are your products made of?
Our products are made from cast stone, hydrostone, various gypsum products, resin, cement, fibers, concrete, polymers, iron oxide, fiber and 30 % limestone aggregate.

AGGREGATES: 

Sand

The sand used in cast stone is shipped in from multiple river beds resulting in a variance in quality. From color the cleanliness each load has its own level of “defect”. 

All manufactures contend with this issue and do their best to carry the cleanest sand and sifting practices. 

Cement

We use a white or grey natural Portland cement and add measured amounts of iron oxide for coloring

Polymers

Our add mixes of polymers are integrally mixed and topically applied after production.

Polymers are used to suspend the composition of molecules in place, prevent efflorescence and promote strength.

Fibers

We use a blend of fine to medium fine chopped fiber integrally to enhance bonding and shear compressive strength.

If material has an occurrence of apparent stains or discolored blemishes within the surface, we will replace those pieces. This is a natural occurrence and is never totally unavoidable. These occurrences are not reason for rejection nor cancellation of orders unless 65% or more is discrepant.

Cure time and climate changes also plays a factor in the integrity and overall quality of material.

What are your color options?
We have various shades of buff, white, black, and red. We can also color match to any of the  Sherwin Williams color palettes.

Color And Finish

Match sample on file in architect’s office.

Units shall exhibit a texture approximately equal to the approved sample when viewed under direct daylight illumination at a 10 ft distance.

• ASTM D2244 permissible variation in color between units of comparable age subjected to similar weathering exposure.
  · Total color difference – not greater than 6 units.
  · Total hue difference – not greater than 2 units.

Minor chipping resulting from shipment and delivery shall not be grounds for rejection. Minor chips shall not be obvious under direct daylight illumination from a 20-ft distance.

The occurrence of crazing or efflorescence shall not constitute a cause for rejection.

Remove cement film, if required, from exposed surfaces prior to packaging for shipment.

Manufacturing Tolerances

Cross section dimensions shall not deviate by more than ±1/8 in. from approved dimensions.

Length of units shall not deviate by more than length/ 360 or ±1/8 in., whichever is greater, not to exceed ±1/4 in.

Maximum length of any unit shall not exceed 15 times the average thickness of such unit unless otherwise agreed by the manufacturer.

Warp, bow or twist of units shall not exceed length/ 360 or ±1/8 in., whichever is greater.

Location of dowel holes, anchor slots, flashing grooves, false joints and similar features – On formed sides of unit, 1/8 in., on unformed sides of unit, 3/8 in. maximum deviation.

Submittal Procedures

Samples: Submit pieces of the Cast Stone that are representative of the general range of finish and color proposed to be furnished for the project.

Shop Drawings: Submit manufacturers shop drawings including profiles, cross-sections, reinforcement, exposed faces, arrangement of joints (optional for standard or semi-custom installations), anchoring methods, anchors (if required), annotation of stone types and their locations.

Economy 

Cost per unit depends greatly on specifications and bid documents. On an average, however, cast stone costs less than quarried stone. 

There are several reasons for this: 

1. It is a molded product and requires no further tooling after the initial pattern is made. Each piece of cut stone must be carved individually. 

2. Freight is also a concern. Usually quarried stone must be hauled over long distances. Most of the limestone in this country is hauled from Indiana. Many stones come from overseas. Brownstone is now typically available from India and Germany. Imported brownstone is beautiful but the cost is several times more. 

Industry standard information can be found at: https://www.caststone.org

Additional Information

We make all products at our Houston, products location. Our products are made of sand, water,  limestone aggregate,  hydrostone, various gypsum products, fibers, iron oxides, polymers and cement. Colors can be selected from the entire Sherwin Williams palette.

American Stonecast, LLC offers a 1 year warranty that guarantees it's product free from any defects that are not considered inherent characteristics of cast stone. This warranty covers only products manufactured by American Stonecast, LLC which are determined to be defective. This warranty does not include damages caused by settlement of the building, failure if the structure (including foundations and walls), and surfaces, efflorescence, oxidation or other causes beyond the control of American Stonecast, LLC.

If you have any questions regarding this warranty, please do not hesitate to contact us Monday - Friday am to 4:00 pm