Thursday24 August 2017

Prefabricated flooring takes off

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With its adoption in two Heathrow terminal buildings, the Technik flooring system is getting a chance to prove itself

After three years of being specified for small receptions and lift lobbies, Technik, the prefabricated floor system, has finally hit the big time with a series of airport installations at Heathrow and Frankfurt. It is being laid at Heathrow’s new Terminal 2B, and in September 14,500sq m of the flooring will be installed at Terminal 5C.

It’s a rewarding time for the team behind Technik — Arup Product Design, contractor Grants of Shoreditch and Lindner, the German interior fit-out company and supplier of the substrate. They have carried out extensive performance testing to convince clients that the floor would perform in heavy traffic.

“In the construction industry it’s quite a step change,” says Rebecca Stewart a designer at Arup’s Product Design division. “It has taken three years to convince people that it does work under the loading. We were having a lot of success with little lobbies, but an airport is a big step up.”

Technik was developed in response to a challenge issued by Stanhope to come up with an alternative to a traditional screed floor for the Foster & Partners-designed Willis headquarters at 51 Lime Street, which was completed in 2007 in the City of London. The developer had been concerned about the messy and time-consuming process of laying floors that can often cause hold ups, and was looking for a more modern system. Recently, the flooring has been used in Arup Associates’ Ropemaker Place office and retail development, which is nearing completion in the City.

“In traditional screed floors you have all sorts of problems,” says Mathias Baumgartner, head of international business at Lindner’s flooring division.

“You come in very late with the wet trades and you cause a lot of humidity and dirt when the building is very busy. All sorts of trades are rushing to finish their jobs and you’re pouring screed that can’t be walked on for days. Often it gets cracked and has to be laid again. The beauty of the Technik product is that we can get away without these risks.”

Arup Product Design worked with Grants to come up with a pre-bonded system that allowed specifiers to choose the material they wanted (granite, marble, ceramic, slate, porcelain etc) but avoid any wet trades during the installation. They used an existing product, Lindner’s tongue-and-groove plasterboard, produced in 600m x 600m panels. The chosen stone is fixed to the substrate using Mapei’s Keralastic synthetic resin fixing and a finish is applied in the factory. A layer of 0.5mm steel plate is added beneath the panel to enhance load capacity to more than 10 kilonewtons. This creates a 50mm-deep panel which can be fixed to the galvanised steel pedestals, also supplied by Lindner and adjustable from 25mm to 2,000mm to suit the contours of the structural floor. The cavity created by the pedestals can be used as an air plenum.

Because of the support structure, the stone can be just 15mm rather than 25mm thick, which leads to an overall 10% weight saving through both the thinner stone and lighter substructure. The Technik team claims other advantages such as the higher quality control of off-site assembly that makes installation easier and does not add to humidity in the building. There is less chance of damage to the brittle finish due to shrinkage. There is also quick access to underfloor services. And crucially, the speedy assembly means a programme saving of 85% on traditional floors since other team members aren’t inconvenienced by the wet floor. Technik can be trafficked with 48 hours of installation compared to conventional screed drying times of one day per millimetre.

Technik system: pedestals support Stone on a calcium sulphate substrate.

Technik system: pedestals support Stone on a calcium sulphate substrate.

Installations at airports also have to contend with the need for a large number of fixings such as posts and desks through the floor. With Technik, these can either be fixed to the underside of the substrate or bolted to the supporting floor. At Heathrow, Arup worked with BAA to install receiving base plates with stone plugs in various “hot-spot” areas within the floor.

Tests at the Building Research Establishment examined the performance of the product’s strength with heavy loads and after soaking. It was found to be able to sustain heavy industrial standards of 20 kilonewtons of load, more than enough for the cherry pickers and other equipment that would pass over an airport floor. After water testing, Technik dried out in approximately 24 hours and was found to lose just 1% of it strength after saturation.

Despite the void beneath the floor, the acoustics are “quite dead”, and no one ever realises they are walking on a void, assures Arup’s Stewart.

According to the Technik team, the prefabricated floor also performs well on cost. In a comparison of the Technik system with a screed-based system, Technik costs £224 per sq m compared with £261 for screed. Although screed is only £7 per sq m more expensive in terms of materials, big savings are made on labour such as tiling, which is £84 per sq m for Technik compared with £114 for screed.

Another cost issue is the larger area that screed materials take up in a warehouse in comparison to the prefabricated Technik system. Production lead times are six weeks and Lindner can produce 1,000 panels a day, including bespoke sizes.

Technik also scores high on sustainability, using up to 50% less stone than traditional stone on screed floors and the simpler on-site installation means there is less wastage through breakages and replacement of tiles that have curled before the screed is completely dry.

In a comparison carried out by Arup of the Technik floor with a traditional system, Technik had a 43% lower carbon footprint — 16.5kg of carbon dioxide per sq m compared with 28.9kg. Calculations for the two systems were done on a cradle-to-grave assessment that looked at carbon emissions associated with getting the flooring to site.

“The UK [construction market] is slightly ahead in time. Prefabrication and green products are a big issue in the UK already. It’s just starting on the continent,” says Lindner’s Baumgartner.

Manufacturing the substrate

The tongue-and-groove substrate is manufactured by Lindner in Bavaria from 95% recycled raw materials including recycled paper from local sources and plaster from flue gas desulphurisation plants.

The paper forms the 15-20% fibre content, while the plaster is used for the gypsum. These two components are mixed together with water and pressed into the mould to create the required density. The raw boards are dried in an oven and then the top and bottom surfaces are ground to get the exact dimensions required. The edges are calibrated then shrink-wrapped on a palette.

For UK Technik projects, they are transported to stone contractor Grants of Shoreditch, which bonds the floor finish to the substrate and installs the system on site using the pedestals also supplied by Lindner. The substrate is also sold separately for use as base boarding for more traditionally installed flooring.

Floor detail

Floor detail

1 Perimeter joint
2 Stone tile
3 Calcium sulphate substrate
4 Joint adhesive
5 Pedestal
6 Pedestal adhesive


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