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Last edited 26 Aug 2021
Natural stone flooring
The term ‘flooring’ refers to the lower enclosing surface of spaces within buildings. This may be part of the floor structure, such as the upper surface of a concrete slab or floor boards, but typically it is a permanent covering laid over the floor. There are many types of flooring materials available including stone.
Stone is a natural substance quarried or mined from the earth. Due to certain inherent characteristics (such as heat retention, durability, ease of cleaning and so on), natural stone may be a desirable material for the production of flooring tiles.
For flooring applications, one important aspect of natural stone is its absorption rating. This refers to the degree to which a material is porous, with the more absorbent being more susceptible to staining and cracking damage. These ratings include:
- Non-vitreous (highest absorption level, making it susceptible to staining, cracking and poor slip resistance).
- Semi-vitreous (less porous, but still susceptible to damage from excessive liquid).
- Vitreous (even less porous than semi-vitreous, making it suitable for low to mid traffic floors).
- Impervious (relatively waterproof, easy to maintain and suitable for high traffic floors).
The major rock groups are igneous, sedimentary and metamorphic. The unique characteristics of each are due to the complex geological processes that have impacted upon it, creating many different types of structure, texture and colour.
A flagstone (sometimes called a ‘flag’) is a flat slab of stone used for paving, walkways, driveways, patios and other outdoor applications. Since the Saxon period, flagstones of various sizes were used for flooring in and around castles and other structures. It has also become popular in modern applications due to its ease of maintenance and affordability.
Traditionally, natural flagstones are quarried from sedimentary rock. This sedimentary rock can have various compositions and characteristics. One of these is the distinct stratification (or bedding planes) which allows the stone to be easily cleaved, i.e readily separated, into largish pieces. It is frequently a fine-grained sandstone interbedded with thin, shaly or micaceous layers, but can also be a limestone.
Depending on the application, flagstone tends to be durable and weather resistant and can be cut into smaller pieces to create interesting patterns. It also provides a naturally slip-resistant finish if properly maintained.
Granite is an igneous rock composed of quartz, mica and feldspar. It has an impervious absorption rating, which makes it suitable for flooring applications that will require good resistance. It is extremely tough and can range in colour from light grey to black, pink, blue and green, according to the mineral content.
Limestone consists of calcium carbonate formed at the bottom of shallow lakes and seas that has been compacted over time. Travertine, another commonly used natural flooring material, is a type of limestone.
The primary source of calcite in limestones is marine organisms although there are other sources. The presence of these organisms means that the stone often has fossil inclusions that form an attractive feature when the stone is polished or honed. It can be categorised as either soft or hard limestone. Various colours can be found as a result of the presence of different minerals in the limestone.
Marble is a metamorphic rock that is predominantly composed of calcite or dolomite crystals. It is characterised by its crystal-like texture which is formed by limestone being changed by a combination of heat and pressure. It is both hard and compact.
Marble has been used as a building material for centuries. As a type of natural stone flooring, it is a classic substance that is associated with elegance. It wears more quickly than granite and is more susceptible to staining.
Sandstone is composed of quartz particles that have eroded from other rocks, commonly granite, and cohered together with natural cement minerals in ground water before being compacted. The stone’s colour depends on the colour of the sand but tends to warm reds, yellows and oranges.
While sandstone can be relatively easy to install, it should not be used in places that experience high foot traffic. It is extremely porous and delicate in comparison to other natural flooring materials and requires considerable care. For instance, solutions that contain acid or alkaline substances should not be used to clean sandstone.
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