How to choose natural stone for projects?



Rogerio Moutinho, MGLW (United Kingdom)

What do architects and designers really look for, when they want to use natural stone?

Without trying to be too simplistic, what one really wants when choosing natural stone for a project is:

1.- A stone with the right colour and pattern

2.- A stone that is suitable or adequate for the purpose, i.e., it is hard enough,not too absorbent, etc.

3.- That the natural stone is fairly easily available, i.e., in the quantity that one requires, and is so within the time frame of the project.

4.- Finally, a natural stone that is affordable or basically that which is within the budget originally allocated.

But before we get into more detail regarding these four points let us also ask ourselves the following question: What comes to your mind when you hear the word NATURAL STONE?

Do you see DESIGN and DECORATION – because you saw a beautiful entrance hall in a hotel, or a showroom with a fine-looking worktop, or even a striking shower cubicle with some exquisitely book-matched veined slabs of an exotic material?

Do you also see ART – the many beautiful sculptures, be antique or modern, are you are able to enjoy as you walk around a city or when visiting a monument?

Do you see it as a BUILDING MATERIAL – how often, as architects or designers, have you stopped to admire a beautiful façade, a rustic wall, a shop-front with a special finish?

Finally, do you see natural stone as HISTORY – nobody can deny that natural stone is an integral part of our heritage. The evidence is there to be seen in every country. As one of the most durable materials, natural stone has always been used for structures (from the pyramids of Egypt to just about any old building in any city), and they are a living testimony of human history.

Because of all these values that it encapsulates, natural stone is really a material like no other.

Now, stone is a natural product, and, as such, it has its own particularities, which means that we must make carefully informed decisions when choosing one for a project. But, going back to the topic – what are the criteria one should take into account when choosing natural stone for a project?

One good method is to make a CHECK LIST that summarises the main criteria. Of course, each point can include many variables depending on the particular situation, but the most important ones are covered here and are valid for most of them.

All these points in the CHECK LIST are all crucial, and they are listed below in no particular order.

1.- Commercial or domestic use

2.- Internal or external application

3.- Special finish requirements

4.- Colour scheme and book matching

5.-Quantity required versus availability

6.- Sampling and viewing the stone in LARGE slabs

7.- Budget

8.- Technical data or tests

Although these are quite self-explanatory, let us go into some detail about each of them.


1.- Commercial or domestic use:

Commercial use implies heavier traffic, which requires a harder-wearing stone. One should not use a soft limestone, no matter how great it looks, on a shopping centre floor, but one can use it for the walls.

On the contrary, for domestic use one has, in theory, the whole array of natural stones to choose from, depending on the purpose: for example, for a kitchen countertop, the best choice remains granite, because its chemical composition makes it less susceptible to staining from acid corrosion.


2.- Internal or external application

With regard to internal use, the only limitations are those we have already looked at.

When it comes to natural stone for external use, the first thing to bear in mind is: is it for wall cladding, or is it for flooring? Most stones are suitable for cladding because water just runs down the walls, but, nevertheless, one should take into consideration the technical data of the stone. For example, the absorption data should be considered. Nowadays, there is a test called ‘salt crystallisation’ which gives one an idea of how the stone will age and wear over time.

As for external flooring, weather factors play an even bigger role. Water, snow and ice (depending on the climate of the place), will remain on the surface and will have a much greater interaction with the stone. In my experience, external flooring in cold climates requires stones which meet the highest specifications.


3.- Special finish requirements

For safety reasons, projects often require a special non-slip surface. In many cases, this implies applying a special finish such as flaming, bush-hammering or sandblasting. But bear in mind that some of these finishes cannot be applied to all the stones.For instance, flaming is out of the question in the majority of limestones.


4.- Colour scheme and book matching

There is always a natural stone for almost every colour scheme in anyone’s project. Stone is a natural product, it comes from a quarry, not a factory line producing perfectly evenly coloured pieces. This natural colour variation makes it unique and gives it its beauty. The issue here is- quantity versus uniformity. If the project is for a large area, one may want to restrict oneself to stones that are naturally more uniform. Additionally, one should be aware of the great potential for effect of book-matching with veined materials (image book-matched material) This can make one´s project really unique because there will be no other set of slabs in the world with the exact same pattern.


5.- Quantity required versus availability

It seems obvious, but many people are often surprised at how often problems arise because of unreasonable expectations around two aspects:

Of any given stone, there are slabs that are more figured and others that are less figured. If one goes for a perfectly clean look, for a larger area, it might be impossible to achieve the required quantity. Nobody will dig out half a mountain to make your dining-room floor.

On the other hand, even without this sort of limitation, when one deals with mega-projects, one must make sure beforehand that the quarry has the capacity to extract the quantity of material required within the required timescale.


6.- Sampling and viewing the stone in LARGE slabs

Continuing from the previous point, it is imperative that one does not make the final decision on using a natural stone based just on a sample. This is, in my opinion, one of the most common mistakes made in the stone industry. Whenever possible, it is highly recommendable to visit the local distributor and see for oneself the large slabs that will give one a much more realistic idea of what the stone will look like in a bigger area, be it flooring, a façade, etc. High quality photographs of slabs can also been seen on the tablets as an alternative, when a personal visit is not possible.


7.- Budget

This is obviously the most self-explanatory point of any check-list. However, it must be said that there is almost always a natural stone for every budget.


8.- Technical data or test

Depending on the project that one is working on, it is important to be aware that quarries are increasingly producing technical data sheets for each type of material, based on lab tests. Since July, 2013 the European Union has making it compulsory for quarries to supply this information.

To sum up, natural stone can add a unique value to a project, it just requires choosing wisely. Please make the most of the knowledge and experience built up over the years by your distributor / natural stone supplier. Visit them, talk to them, feel the natural stone, ask all the questions, no matter how simple they might seem. And if there is a particularly complicated requirement, your stone supplier is there to get for you all the answers directly from the quarries.

A project in natural stone highlights the uniqueness of not just the stone, but of the whole project itself. Make the choice the proper way- and you will be even more proud of what you have built.