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Green Underfoot

15 June 2009

Ropemaker Place, London

Using a by-product of coal-fired power stations and recycled paper as a substrate for stone flooring
provides a green alternative to using screed as a base, and can significantly improve the carbon
footprint of stone flooring used in high profile locations from office foyers to airport terminals

HARD FLOORING IS NOT NORMALLY an area of specification where one would expect to pick up ‘Greenie points’, but a Technik, flooring product designed and developed by Arup’s industrial design department and manufactured by stone flooring specialists Grant’s of Shoreditch, may well change all that.

The story goes back to 2005 when Grants and Arup’s Materials Consulting experts needed to find a quick-to-install, prefabricated flooring system carrying the highest quality stone finish for a Stanhope development. Using of tongued and grooved flooring panels, they came up with a prefabricated flooring panel system that has all the advantages of raised access floors yet carries the solidity and elegance of a genuine natural stone tile.

The tile is laid on a tongue and groove substrate panel which is carried on plinths exactly like a raised access floor. Once the stone finish tile is installed there is no possibility to raise and lower the units as if it was an access floor, but up to that point the advantages are numerous.

Arup’s own carbon assessment of the product’s green credentials compares it with a conventional stone-tile-on-screed installation, with a screed thickness of 83mm. The stone tile itself is left out of the comparison, since it is common to both types of installation. This study concluded a ‘carbon footprint’ result of 16.5kg per sq m for Technik compared to 28.9kg per sq m for the screed option – most of which is due to the screed itself.

The substrate, or tile board, manufactured by German company Lindner. It is made of amixture of gypsum which is produced by ‘desulphurisation’ of the flues in coal-fired power stations, and recycled paper. The two materials combined mean the substrate is 95 percent recycled.

In addition, Technik’s advantages of on-site speed and flexibility are not usually associated with high quality hard surfaces which depend on adhesives and screeds (often noxious), long drying times, and perhaps most important, high skill levels. It is not as sensitive to onsite temperature and humidity, and indeed with no screed and minimal use of adhesive (only the plinth pedestals are glued to the underfloor), the system doesn’t add humidity to the site interior.

Installation can be carried out by less skilled operatives and the dry installation also means that other trades can continue to work alongside, making shorter programme times for the entire project. In fact Technik can be trafficked just 48 hours after installation, compared with several days for conventional screed floors. Grants claim that installation can be up to 15 times faster than floors using traditional bedding methods.

Under-floor services remain accessible; there is no ‘lipping’ of laid stone panels; there is no risk of damage to the brittle finish from shrinkage or compacting of the substrate; and because it is a factory made product, the uniformity and regularity of tile size and the panel to panel joint make for a neat and beautiful installation.

According to Grants’ own standard criteria Technik’s cost base gives a seven percent improvement on that of conventional floors. ‘For a stone tile finish with a finished floor level150mm above the structural slab,’ says Grants’ James Smith, ‘Technik costs £230 per sq m and the screeded product £246.’

The enormous development at Ropemaker Place in the City of London for instance, uses Chinese granite, while Paternoster Square, next to St Paul’s in London is sandstone. Ropemaker, in fact, has been the subject of a WRAP (Waste & Resources Action Programme) analysis.

Ropemaker, designed by Arup Associates, is a British Land speculative commercial building with 586,000 sq ft net lettable space over 21 storeys and three basement levels. The high profile development already has impressive green credentials, including a BREEAM ‘excellent’ rating. One of the products assessed at Ropemaker was the Technik flooring.

According to the manufacturers and to the WRAP study, the advantages over traditional methods are:
● The required thickness of the finished stone is reduced
● A significant proportion of component parts are recycled
● Shortened construction period (no drying time as with traditional screed)
● Minimal off cuts on site
● No requirement for special machinery.
Technik performed significantly better in terms of waste. Against an estimated waste level of 41 sq m of waste for screeded floor, Technik generated 24.5 sq m of waste over the entire site. In addition, screeded floor generates a large amount of polystyrene offcuts when standard size sheets are cut on site. Technik flooring considerably reduces offcuts and therefore site waste. Progress has also been made in reducing
packaging waste.

As is often the case with environmental concerns, things can be complex when it comes to looking at the performance of materials. BRE ‘Ecopoints’ measure the overall environmental impact of a product, covering a range of 12 issues as well as CO2 emissions including mineral depletion and water extraction. So while the strictly CO2 impact of the Technik flooring system as installed in Ropemaker is higher than that of the screed, the overall environmental impact of the Technik floor (calculated in Ecopoints per tonne) is lower. The higher CO2 impact of Technik is mainly due to transport to site, while screed’s higher overall impact is due to its greater use of resources.

Overall Technik was found to be the cheaper option at Ropemaker Place. In the stages of laying the screed floor, the tiling costs the most both in terms of materials and labour, pushing the price of the traditional floor up. Additionally, the materials associated with the traditional screed design take up a greater area within a warehouse and as such the cost is considerably higher than that of Technik floor.

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