Slate as Paving
Although slate is mainly used in roofing projects, due to its thin, strong, waterproof properties,
it is often used as a paving material, and has been used as such for many centuries. It is a
metamorphic rock, comprised of shale that is easily rived, or split, due to its foliated nature
– being formed in thin sheets, ranging from paper thick to over ninety centimetres, making it
suitable for all kinds of projects.
When used in roofing, the sheets are cropped using a guillotine, leaving a sheared edge.
Paving slates however, tend to be sawn four sides, i.e. the dimensional sides, split or riven to
thicknesses of around 20mm. (Thinner slabs may be used for internal projects. These would
be considered as Tiles and fall under BS5385.) (See Tiling British Standards.)
Although slate has very low water absorbency, the potential for water entering the foliated
layers of the sawn edged slab can become problematic if the joints are not fully filled with
an impermeable grout or joint compound.
Slate is a hard-wearing material, although it can become slippery under foot, especially when
used as steps or areas of high pedestrian traffic due to its smooth surface. As a general rule
however, it does have anti-slip properties, and provided a fall of 1:60 is maintained to dispel
surface water, it is a useful material.
It is easy to clean, with the surface drying off quite quickly. The use of sealants may increase
the slipperiness of the surface, and care should be taken to use a breathable impregnating
sealer. Take advice from the supplier before applying any form of colour enhancer or sealant,
especially on slate paving.
