A New Life for Limestone

Specification involves decision making and in many ways a process of elimination, in the same way that you trawl the entire assemblage of high street stores with your partner seemingly in search of the holy grail, only to find yourself back at your first port of call purchasing their initial object of desire. (This purely from a male perspective, of course!) During the journey you will have hinted at, or at least leant towards, a particular choice of object in the hope of short cutting the elimination process.

As an interior design specifier you endure these journeys daily, swapping roles with your partner, your own role being taken on by a never ending stream of salespeople and glossy brochures. Relying on instinct, information, budget, and if you’re fortunate, previous experience of a particular product or material, you reach a decision. You could argue that by sticking to a tried and tested palette of materials you could expect to guarantee reliability, performance and ultimately the success of a proven formulae. But by the same token you might argue that familiarity can breed repetitiveness and in many instances you can ‘expect the expected’. My own feeling is that as an architect or designer, you have a duty based on your acquired knowledge and experience to push the boundaries and limitations within our respective fields, and to strive for interesting, intelligent, coherent and if possible unexpected solutions. To consistently do this, however, ultimately entails an element of risk, and it is at this stage that you place your trust in the hands of the suppliers, manufacturers and installers.

In recent times limestone has been a material whose performance in commercial use has suffered severely in terms of bad press. On occasion limestone falls into the category of ‘design from photography’, which occurs when designers, architects and other specifiers judge the suitability of certain materials partly on the basis of their inclusion within certain well published projects. It had been viewed wrongly as a cheap alternative to marble and dumped into the UK market on the back of projects such as the ‘Grand Louvre’ completed in 1993 by JM Pei. Some of the softer, cheaper Spanish, Portuguese and French stones were never intended to be used on floors but poor marketing and uniformed specifiers wrongly selected them, resulting in the aforementioned bad press to the extent that in some practices specification of limestone is banned. The most common failures in the faulty stones were discolouration, surface breakdown, pitting and inability to clean, and yet most stones were given test certificates.

Domus Tiles recently enlisted the help of eminent geologist Kip Jeffrey to evaluate the performance of an extensive range of limestone under stringent criteria to provide two ranges of high quality durable flooring tiles. Testing was carried out on over one hundred stones and to date only eleven have met the Domus criteria, (understandable when you consider that chalk is a form of limestone.) That isn’t to say that other suppliers don’t have suitable ranges of commercial limestone available, but my own experience of limestone has been limited to the Domus range which was specified recently in Tun Ton Restaurant in Glasgow by Graven Images, and to date has performed well. Domus have provided a fairly extensive brochure relating to this particular subject which explains in simple terms their own range, criteria and methods of testing limestone, while for the stone boffins out there the importance of microstructure, microposity and mineralogy are also discussed.

The great pyramids Cheops in Egypt has almost 2.5 million limestone blocks, some weighing up to 70 tonnes. The tolerance of these blocks—plus or minus 1mm—surpasses even modern day technology when you consider that a 300x300mm square limestone tile, machine manufactured today has a similar tolerance. The complexity and precision achieved in constructing this Egyptian colossus is further highlighted by the fact that a thin layer of hard limestone veneer was added on top of the softer core of limestone block, initially for greater durability but also for the reflective qualities of the harder stone which would have cast an enormous glow from the pyramids as the sun rose.