In this regular column, Consultant Barry Hunt answers reader enquiries. If you have a question, email it to: nss@qmj.co.uk marked for Barry\'s attention

Am I asking for trouble if I use limestone tiling in a shower enclosure?

You are not asking for trouble if you select the right limestone and follow appropriate guidance - specifically that in BS 5385, which covers tiling in areas subjected to regular wetting.

However, cutting any corners with the installation of limestone is more liable to land you with problems than with stones that are non-porous.

It is essential that limestone is properly sealed for use in such an environment. But limestones have a wide range of properties and a sealer that works well with one will not necessarily work as well with another.

Also, some sealants may not perform well where there are other chemicals present such as those found in soaps and detergents that will inevitably be used in a shower.

Generally, the more porous (and often cheaper) limestones are better avoided as they are harder to seal fully.

The structure of the shower must be dimensionally stable in the presence of moisture with the outer surface made to be as water-resisting as possible.

It would be best to tile on to sand/cement rendering or dense concrete, but partitioning may mean that sheets or boards form the background, increasing the risk of problems.

Any plywood used should be of good quality and water and boil proof. All nails, screws or other fixings should be oxidation resistant.

Tanking (a waterproof lining) is not a necessity but would provide additional reassurance for partitioned walls. This could take the combined form of a decoupling membrane and thus provide additional relief from the heating and cooling stresses experienced during normal regular use.

Special care must be taken at the junction between the stone and shower tray where moisture could rise behind the tiled surface. If it does, it is unable to escape because of the surface sealing of the stone tile.

Spot bedding is not acceptable, even if large slabs are used. Achieving a full bed is essential to prevent potential accumulation of moisture behind the tiles and related damp and discoloration issues.

Limestone tiles often have dusty backs and it is essential this dust is washed off immediately prior to use. Cleaning also helps to reduce potential suction effects and it is recommended that a thin \'butter\' layer of adhesive be applied directly to the backs of limestone tiles to ensure full and strong adhesion is achieved.

Tile spacers should be avoided and pegs used instead. Spacers are often left in place and provide potential grout failure points and easy conduits for moisture transmission.

Reference: BS 5385:Part 4:1992. Wall and floor tiling. Code of practice for tiling and mosaics in specific conditions. Published by the British Standards Institution, London, England.