Why Cast Stone?

According to the Cast Stone Institute:

"Cast Stone has been a prime building material for hundreds of years. The earliest known use of Cast Stone dates about to the year 1138 and  was seen at Carcassonne, France, the Cité which contains the finest  remains of medieval fortification in Europe. Cast Stone was first used  extensively in London in the year 1900 and gained widespread acceptance  in America in 1920."

https://www.caststone.org/history.htm

"The two basic cast stone production systems were 'dry tamp' and 'wet  cast.' The dry tamp process employed a stiff, low slump concrete mix  that was pressed and compacted into the molds. The decorative aggregate  mix was frequently distributed only on the exterior facing of the cast  units, while the cores of the units were common concrete. After a short  time, the units were removed from the molds and often cured in steam  rooms to assure proper hydration of the cement. The wet cast process, on  the other hand, used a much more plastic concrete mix that could be  poured and vibrated into the molds. This system used significantly more  water in the mix, assuring proper hydration of the cement mix without  elaborate curing, but requiring that the units be left in the molds for  at least a day. Through this method of fabrication wet cast products  distributed their decorative aggregate mix through the entire unit,  rather than simply an outer facing."
 

High quality cast stone was frequently 'cut' or tooled with pneumatic  chisels and hammers similar to those used to cut natural stone. In some  cases, rows of small masonry blades were used to create shallow parallel  grooves similar to lineal chisel marks. The results were often  strikingly similar in appearance to natural stone. Machine and hand  tooling were expensive, however, and simple molded cut cast stone was  sometimes only slightly less costly than similar work in limestone.  Significant savings could be achieved over the cost of natural stone  when repetitive units of ornate carved trim were required."

https://www.nps.gov/articles/000/cast-stone.htm

"Cast stone was first discovered in ancient Rome, where pozzolanic  cement was mixed with natural aggregates such as natural stone and  broken bricks. This helped the Romans create a new material, opus  caementicium, which would be used as an alternative where quarried stone  would have been used. For example, this new material would have been  used to create the vaulted arches or gateways of the Colosseums.

In 1138, cast stone was used in the medieval wall for the city of  Carcassonne in France. As part of the wall repairs, lintels were cast  from a natural stone alternative, where lime-pozzolan cement was mixed  with natural aggregates. By now, cast stone was used across many  European countries."

https://www.clickcaststone.co.uk/blog/cast-stone-history/

The term ‘natural stone’ refers to any product that is quarried from the earth.

It  is widely recognized that natural stone is a strong, stable and  timeless building material. Popular natural stones including, granite,  marble, limestone, travertine, slate and sandstone, have been used as  building materials for thousands of years, creating some of the most  famous historic structures, monuments and works of art around the world.

As  a natural material that has gone through many changes over time,  natural stone offers variations in both colour and grain pattern, which  when used correctly requires minimal maintenance.

Cost is usually  the most prohibitive factor when deciding to use natural stone on a  project. The process of extraction, cutting and finishing the stone can  be comparatively more expensive and time consuming than producing cast  stone. In addition, while locally sourced UK stone options are  available, popular stones from abroad are often imported from China,  Italy and Turkey, increasing the carbon footprint of the material.

Cast stone is an appealing alternative to natural  stone, produced in moulds using high quality fine and course aggregates,  designed to simulate natural cut stone. It can be manufactured to  produce architectural features that will enhance new buildings or match  existing stonework on restoration projects and is regularly used and  accepted in areas with sensitive planning constraints.

As well as  being both superior in strength and comparably more cost-effective,  there are several additional benefits of using cast stone over natural  stone:

• Specifying cast stone allows the designer the ultimate  freedom to achieve the aesthetic they desire without restriction. Using  the highest quality molds made from solid timber, steel, fiberglass or  polyurethane allows us to achieve crisp arises, beautiful curves and  fine decorative details.
• Using specialist mixing methods in both  or wet cast and semi-dry products achieves consistency in stone color,  free of the naturally occurring variations or imperfections found in  natural stone. In addition, the reduced moisture absorption of cast  stone results in improved freeze/thaw durability over natural stone.
• Cast stone can be produced and delivered to site in a much  shorter time frame and requires minimal maintenance during its lifetime.  Steel components such as reinforcement and fixings can be included in  the product during the casting process, making it possible to produce  structural stone that negates the need for any additional support,  bringing significant associated construction and economic benefits.

Often,  the choice between natural and cast stone products comes down to  personal preference and the constraining parameters of each individual  project, such as time-scales and budgets.