What is sandstone?
Sandstone is a natural stone made of sand grains, usually quartz, bound together by a natural cementing material. It is a sedimentary rock: sand once deposited in seas, rivers or deserts that later hardened under pressure and through mineral cement. The binder can be calcareous, clayey or siliceous, for example. Iron-rich sandstone is coloured red, brown or purple.
Properties
- Variable durability: this depends heavily on the binder and the quarry. Some sandstones weather within a few decades, others last for centuries.
- Porous: sandstone absorbs water, so frost, salts and pollution can cause damage.
- Easy to work: sandstone is relatively easy to dress and carve.
- Discolouration: over the years sandstone often darkens, sometimes to black, through soiling and patina.
Application
Sandstone was often combined with brickwork, for example for string courses, quoins, window and door surrounds and ornaments. It is also used for plinths, window sills, steps, flooring and sculpture. Well-known types in the Netherlands include the yellowish Bentheim and Gildehaus sandstones from just across the German border, formed in the Lower Cretaceous.
Maintenance and repair tips
- Do not confuse it with sand-lime brick: sand-lime brick is a manufactured building block of lime and sand, not natural stone.
- Clean gently: aggressive high-pressure washing or sandblasting destroys the stone surface. Leave cleaning to a specialist.
- Use a softer mortar: for pointing and repairs, use a mortar that is softer and more vapour-permeable than the stone. Hard cement mortar makes the stone itself fail.
- Match replacements: when replacing stone, choose one with similar properties and appearance. For listed buildings, agree this with the heritage authority.
- Shed water: make sure copings and drips drain well, so the stone does not stay wet.
Related terms
- Quartz
- Quartzite
- Iron sandstone
- Lime mortar
- Natural stone maintenance
- Natural stone replacement
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