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Steve Turner By Steve Turner • March 14, 2017

How to choose French Limestone for major projects

Cutting and finishing large volumes of French limestone

 

On our blog, we've talked about some of the different types of French limestone and the quarries they come from. But the factories that cut and finish the stone tend not to be mentioned very much.  However, they are such a vitally important part of the process that we thought we should highlight what to look for and why.

For major projects that use French limestone, it goes without saying that the specifier has to choose the right type of stone that suits the technical and aesthetic requirements of the project.  But there are other considerations that could have an impact on the larger projects.

French limestone stone cutting factory
Cutting blocks of Tuffeau French limestone for masonry projects

Quarry Capacity

For the very large projects requiring large volumes of stone, it is important to know that there is enough raw material in the quarry to fulfil the requirement and that it can be extracted in the necessary timescales.  The size of the "bench" or layer of the chosen stone should also be taken into account.  Each bench of stone can have very different characteristics and they are not necessarily interchangeable.  The technical qualities of each bench may be different as well as the aesthetic qualities.

Chauvigny quarry - French limestone
Chauvigny Quarry - "Gold" bench above and "White" bench beneath our feet

Quarry Bench Height

The height of each bench or bed ("banc" in French) is a further consideration.  Some benches are just a few centimetres thick and some are several metres thick.  Stonemasons will recognise this as an important factor when choosing stone for larger structural pieces, such as supporting columns.  Generally, stone is stronger and less compressible when it is installed the same way up as it lies in the bed.  For example, a tall bed height means that a supporting column could be delivered in a single piece of stone instead of several smaller pieces. 

Factory Machinery

Most of the companies that own quarries also own a factory where the excavated raw stone blocks are cut and processed.  The equipment in the factory is often determined by the use that the stone is normally put to.  For example, if the stone is particularly suited to flooring, then the company will probably have invested in a tile line machine specifically to cut and finish floor tiles.  Or, if the stone is great for carving and monumental pieces, they will more likely be focussed on cutting "6 sides sawn" blocks for the stonemasonry market.

The question here is; does the factory have an adequate number of machines of the right type to keep up with the production rate or would it have an impact on the project's critical path timeline?

Curved slabs of French LimestoneIn order to produce cut to size sculpted pieces, e.g. fluted columns or coping stones, the raw block would be cut "6 sides sawn" on a block cutter and then moved onto a CNC machine or perhaps a stone lathe.  After that, it may be finished by hand.  Does the factory have enough block cutters or enough CNC machines and then enough masons to complete the work within the required project timescales?  Sometimes, the cutting and finishing work can be outsourced by the quarry to other companies.  The key question then is, how much control does the quarry have over the outsourced supplier?

In the small image here, you can see the curved finished pieces that were cut by the CNC wire saw in the larger photo below.  To meet the production deadline, the raw blocks were first cut to size by several block cutters before being shaped by one of the 3 wire saws (below).  They were then cut to width and length by a further set of block cutters before being honed by hand and then packed and wrapped ready for despatch.

CNC wire saw cutting French limestone curved slabs
One of three CNC Wire Saws cutting curved slabs of French Limestone for a major project

The whole production process should be considered when planning large scale projects and it is worth ensuring that the quarry company already has experience of such projects.  

Our French partners include the largest limestone quarry companies in France and they have supplied limestone to some of the world's greatest natural stone projects.  It is used in historic buildings and new builds alike, from Canterbury Cathedral to Canary Wharf and in the UK's most sought-after residential locations as well as in significant buildings around the world.

If you think French limestone could be suitable for your project, please get in touch and we will help you identify the right stone, the right quarry and the right factory to meet your project requirements.

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