The use of slate for flooring and paving, probably dates back to an age long before its properties became known for use as a roofing material. It is extremely durable and many examples of centuries old traditional, flagged cottages can still be seen.
However, cost is an important factor today and it is obviously more economic to use smaller and thinner pieces. This thinking, encouraged by an obvious market for slate flooring, brought about the now standard 300 x 300mm tile. This has a riven finish to both faces and a nominal thickness of 12mm. The edges are sawn square.
The natural cleavage of the slate gives a textured finish which provides considerable grip and the very nature of its production ensures a variation to every tile that is subtly different.
Slate flooring forms a durable and hard wearing surface and at the same time gives a pleasing and unusual appearance at an economic price, it is ideal for large areas of interior and exterior application.
A standard size of 300 x 300 x 12mm is recommended for ease of handling (thickness is nominal). Various other sizes can also be supplied against specific orders. A specific suggestion is to use tiles with three set widths of 100, 150 and 200mm laid side by side, but with their lengths in random sizes.
Natural riven slate is ideal as it provides an excellent non slip surface. Fine rubbed and sanded finishes are also available.
The standard size is readily available and large contracts can be supplied in a comparatively short period of time. Larger slabs can also be obtained with reasonable notice of delivery dates.
For design considerations see BS 5385 Part 5: 1990
The preparation and requirements for the substrate upon which the floor is to be laid are of the utmost importance. Consideration should be given to floor loadings, possible movement of structure, overall depth of finish etc., In conjunction with the type of floor required.
Here we only have space to consider the general needs in laying a standard module 300 x 300 x 12mm (nominal) riven floor but many of the principles are the same. Generally, this type of floor is laid upon a concrete or rough screened substrate, which should be set approximately 40mm below required finished floor level, and incorporate any falls that may be required. The substrate should be sound and free from any materials which might impair the future performance of the finished floor.
Bedding is normally a 25 – 30mm depth of semi dry sand / cement mortar 4:1. Sand should ideally be fine and sharp; (small aggregates could make laying difficult) cement should be ordinary Portland. This should then be spread over the previously dampened substrate. The preferred side of the slate tile should be uppermost and the reverse side covered in a neat, Portland slurry of trowelable consistency. it should then be tamped firmly into bed, ensuring that it is consolidated and, as free as possible from voids and hollows. Most floors are laid to a “broken joint” pattern but this can be varied if desired. Jointing is normally tight butted although coloured cement joints (min 5mm) can provide an attractive alternative. Any structural movement joints should always be taken into account and dealt with in the appropriate manner. this type of floor may also be laid upon other types of substrate such as marine plywood and, also, some thin bed adhesives may successfully be used. However, it is advised that expert consultation should be sought before a final decision is made.
Care should be exercised when laying the floor; to keep the surface of the slate as clean as possible. Any cement or grout should be removed before it dries, using clean water and a sponge. The sponge should only be wet enough to do the job effectively. Once laid the floor should, if necessary, be protected from any further building work, with a suitable temporary covering until the job is complete.
To maintain the satisfactory appearance of a Natural Riven slate floor, all that should be required, is firstly to thoroughly sweep or vacuum the area, after which it may be washed over with clean water. Again the cleaning utensil should only be made wet enough as to be effective.
Cement, plaster, alts etc., may be removed with a proprietary brick cleaner obtainable from builders merchants. Manufacturers instructions in all aspects of use should be adhered to. The use of a wire brush or wire wool is sometimes helpful in the operation. Ensure all traces of cleaner are removed with clean water.
Grease: this can in most cases be removes with a detergent and water. Wash over with clean water.
Paint etc.: this can be removed with a propriety stripper (preferably water solvent) and scrubbing brush. Manufacturers’ instructions in all aspects of use should be adhered to. Wash off with clean water.
General dirt etc.: most other marks can be removed with clean water, or at the most, a mild detergent. Wash over with clean water.
On completion, and is so desired, the floor may be finished using a clear sealer; either polymer, oil or spirit based. the appropriate type should be advised by the floor layer. These usually give a middle glazed appearance and also darken the slate when wet. This operation should only be carried out when slate and bed are completely dry. Once floor has been sealed it will, of course, require additional periodic treatment according to the amount of traffic it receives. Once sealed, the appearance can be maintained by the application from time to time of a proprietary polish. A polish which has been found satisfactory over the years is a metalised emulsion.
Once the finish has been brought to the required level, occasional buffing with an electric floor polisher should maintain the appearance. Application according to maker’s instructions.
It should be noted that all polishes give an increasing shine.
When specifying remember to ask for:- Wincilate “Best Quality Welsh Slate Flooring”
Wincilate flooring may be seen at:
- The Museum of London, Barbican
- Victoria & Albert Museum, Kensington (Jewel Gallery)
- Wedgewood, Barlaston
- Crown House, Cardiff
- St Mary’s Church, Thame, Oxford
- St Pauls Church, Brentford