SPECIAL SITUATIONS
Wet rooms - All areas subjected to regular wetting, such as shower enclosures, require special consideration to prevent moisture damaging the substrate whether it is cement or timber based. The process of ensuring the substrate is totally protected from moisture is called tanking. Kirkstone offer a proprietary tanking system called Lastogum, which provides an impenetrable membrane that can be tiled onto with standard adhesives such as Tilefast 6. Whilst the tanking will prevent moisture damaging the substrate, it is still recommended to thoroughly seal stone used in such locations. It is also suggested that Admix (a waterproofing additive) is used in the grout and adhesive, as this will help reduce permeability.
Underfloor Heating - The fact that stone retains heat well makes it an excellent surface when used in conjunction with underfloor heating. In general, there are two basic systems available - a hot water pipe system, which requires a minimum of 10mm of space/screed to lay the pipes in, or an electric mat system, which is laid within the adhesive bed and only adds 3mm to the overall thickness of the flooring zone. For further details please consult manufacturers of the relevant systems.
GROUTS AND JOINTS
Movement Joints - These are required to avoid stresses that can arise in both floors and walls as a result of a structural movement, thermal variations, changes in moisture content and deflection under load. All of these can cause loss of adhesion, and may also result in bulging or cracking to both vertical and horizontal surfaces.
Movement joints should pass from finished surface through the bed to the substrate. They may be left open throughout the construction, or cleaned out and filled with a non-staining grade sealant. Alternatively, they may incorporate proprietary non-corrosive metal performance strips. These strips need to be laid as the work progresses.
Flexible perimeter joints 10mm wide, but certainly not less than 6mm are generally required to be installed to the margins of all floors greater than 2m between restraining surfaces (e.g. walls). For floors with restraining surfaces greater than 10m apart, flexible intermediate joints are also necessary. The intermediate joints should be 6mm wide and no more than 10m apart (15m apart for external paving). In timber floor installations, it is preferable if the joints can be lined up with a counterpart on the tile backer board. For full protection the sealant must then be continued through into this joint.
Tile Joints - To allow for minor tolerances on smooth finished stones and to permit the introduction of a jointing medium, a narrow joint of not less than 3mm is required. For textured stones and natural cleft surfaces, joints are recommended to be between 6mm and 10mm wide. In these cases, a modified grout may be required to minimise shrinkage. Our collection of antiqued tiles have a small degree of variance in size and squareness. Consequently joints are recommended to be 4mm to 6mm wide. The joints should be completely filled by working the grout, e.g. Groutfast 8 into the joint. As some stones are naturally more absorbent than others, care should be taken to ensure the grout is of a similar colour to the stone (a range of grouts are available from Kirkstone). All grout residues should be wiped off the surface of the stone before it is allowed to harden.
PROTECTION
If a stone floor is to look and perform to expectations, it is imperative to allow the installer ample time to lay, clean, seal and protect the floor without interference from any finishing trades. Sufficient time should be agreed and written into the programme of works, prior to the contract being accepted.
The protection of finished and partially finished flooring from damage or contamination by following trades is of paramount importance. During the laying operation and for a full 4 days afterwards (24 hours if using adhesives), the areas that are being treated should be accessible to no one other than flooring operatives. Light pedestrian traffic may be allowed onto a finished floor after this period, but the floor must be kept clean and protected until all construction, electrical and decoration activities have been completed.
USEFUL REFERENCES
British Standards
BS 5385 - Wall and Floor Tiling. Code of practice for design and installation.
Part 1: 1995 Internal ceramic and natural stone wall tiling and mosaics in normal conditions.
Part 2: 1991 External ceramic wall tiling and mosaics (including terracotta).
Part 3: 1989 Ceramic floor tiles and mosaics.
Part 4: 1992 Tiling and mosaics in specific conditions.
Part 5: 1994 Terrazzo tile and slab, natural stone and composition block flooring.
BS 8000: Part 11 - Workmanship on building sites. Code of practice for wall and floor tiling.
Section 11.1: 1989 (1995) Ceramic tiles, terrazzo tiles and mosaics.
Section 11.2: 1990 Natural stone tiles.
Adhesives, Grouts and Sealants - Product names shown in italics are available from Kirkstone. Please contact our Head Office sales team on 015394 33296 for further sales and technical information on any of our products.
Source: Kirkstone.com