Understanding hardscaping materials and tips on installation

Sandstone

Sandstone is a sedimentary rock primarily composed of small grains of minerals, which have been weathered by the elements and transported by rain, wind, and ice. The deposited grains collect in layers and become compacted under pressure, while overlying deposits continue to accumulate. Various minerals that migrate into the voids or pores of the deposits cement the grains together.

Although sandstone is a relativity soft material, it yields high compression strength and has a low absorption rate making it ideal for construction and use in freeze-thaw conditions. It is highly resistant to weathering and tends to heighten in colour and appearance as the stone ages. Imported sandstone from Asia has become a popular paver material in North America. Variations of the material can closely blend in with many of North America’s local stone materials, but yield a more affordable price.

Deposits of sandstone can be found in a variety of colours with a single-source deposit offering numerous shades and veining. Iron oxides, manganese oxides, and other impurities can cause bright and contrasting colours in sandstones. Globally, sandstone can be found in a range of vibrant colours—from tan, brown, yellow, red, pink, white, grey, and black. In some cases, certain colours can be easily associated with their geographic source deposits, which are found globally, with primary deposits located in the U.S., India, China, Brazil, and Germany.

Slate

Slate is a metamorphic rock derived from deposits of the sedimentary rock shale. Shale is formed from layers of sediment; primarily silt and clay are deposited and compacted together. When shale is subject to heat and pressure it metamorphoses into the more dense and durable slate.

This material is most commonly used in flooring, paving stones, and as roofing tiles. A great attribute to slate is the ability to split the stone into layers, giving it a natural textured surface, yet remaining quite smooth and flat. Slate is virtually waterproof with a low water absorption rate making it impervious to freeze-thaw cycles.

This material does vary in colour; however, the most abundant is grey. Deposits of green, purple, blue, and black are also common.

Spain is the leading producer and exporter of natural slate materials followed by Brazil. Substantial deposits are also found in the eastern U.S., in a region known as the ‘slate belt,’ comprising the states of New York, Pennsylvania, Vermont, Maine, and extending into Canada in the province of Newfoundland. China and India have also become large exporters of this stone.

Manufacturing and quarrying

The manufacturing and quarrying of natural stone pavers varies depending on the desired product and geographic source location. For the most part, operating quarries around the world function in a similar fashion. Quarries extract various stone materials, which are cut into slabs or cubes, which are then sent to a processing facility where they are cut or split into standard and custom sizes.

Standard sizes (length x width) range between 300 x 300 mm (11.8 x 11.8 in.) and 600 x 900 mm (23.6 x 35.4 in.). Most pavers are cut or split to a thickness between 25.4 mm (1 in.) and 50.8 mm (2 in.). A natural split stone may vary between 25 mm (0.98 in.) and 35 mm (1.37 in.) thick, while calibrated cut stones have a more exact tolerance of 25 mm (0.98 in.), plus or minus 1 mm (0.03 in.).

The variation of thickness depends on the intended application of the product and the desired appearance. Since the stone is quarried and cut to size, an almost limitless option for customization is possible. Post cutting, different finishing processes are applied to the stone to give the material its final texture and appearance. Common finishing processes include natural split, flamed, honed, sandblasted, bush-hammered, and antiqued.