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Berlin-Pankow Underground

Berlin-Pankow Underground Special Construction for the laying of glass tiling

  • Building Type: Others
  • Pad: Coverings and Tiles
  • Solution: Sound Proofing / Insulation
  • Brand: Codex
  • City: 10000
  • Country: International

In ensuring, for the future, quality of life at a high level for the people in the Berlin region, the Berlin public transport system is particularly significant, thanks to the increase in traffic generally. An important pre-requisite is an attractive range of transport with a tailored infrastructure. The ongoing development of that infrastructure requires future expansion of the existing lines in the Underground network.

With the extension of Line U2 from the Vinetastraße Underground to the North to the new Pankow Urban and Underground Railway, one year before the 100th anniversary of the Berlin Underground, a new network link is being formed.

Start of construction of the Pankow Underground was in 1998. The Pankow Underground was commissioned for use on 16 September 2000. In the design of the station, the commissioners – the Berlin Transport Service – and the appointed architect practice, Figallo, Birkel & Partner, chose light and transparency which had to be created, amongst other means, by the use of glass tiling on the walls and pillars.

Special Features and Base Construction for Glass Tiling
The choice for the wall claddings was fully pigmented, white glass tiles. In the 50's and 60's, glass tiling was often used for wall claddings because of its resistance to frost and acids and because it was easy to maintain. It had the advantage that, because of its homogeneous construction, it eliminated any stresses between the pot and the glaze. The main problem, however, was the lack of flexibility of the glass tiles, which cracked due to stresses in the substrate.

Despite the stated advantages, glass tiling still has today the problem of a lack of flexibility – especially where there is vibration as with passing Underground trains. For this reason, Bernd Burkel, construction manager for the tiling company Junck from Berlin, worked in close co-operation with the codex Technical Division. They decided, for the base construction, to use a render that was not bonded to the concrete, so as to accommodate the lack of flexibility – "unique and a one-off" is how Herr Burkel described the special construction.

Therefore, un-gritted 300 gauge board was nailed to the concrete walls and pillars to form a barrier. Using dowels, screws and spacers, the reinforcement mesh was fixed. Reinforcement and glass-fibre has the job of increasing the structural strength and eliminating crack formation.

The construction comprised two layers of render, consisting of a basecoat and a topcoat of cement-lime render with a combined thickness of 35 millimetres. Overall, the total special construction was 50 millimetres. The construction, developed by Junck and codex, ensured that the vibrations from the Underground trains caused no damage to the glass tiling.

In total, approx. 1,200 m2 of glass tiling was fixed to walls and concrete pillars. The tiling work was carried out on scaffolding, often in the narrowest of locations.

The tiling was white Schudoplack glass tiles from the company Scholl, Kassel in the Hanover style, 30 x 60 centimetre with fluted backing. For the wall surfaces that are exposed to heaviest use – for example on the staircase exits and the waiting areas on the platforms – nine millimetre ESG safety glass was used and, for other areas, six millimetre standard glass was selected. The single-pane ESG safety glass has high resistance to temperature changes, increased resistance to impact and shock and high tensile bending strength.  The advantage of its use in the Pankow Underground was also based on the fact that the ESG glass, in the event of breakage, produces a fine network of broken pieces that are mainly blunt-edged and, therefore, present no risk of injury.

In addition to the previously mentioned advantages, glass tiling is ideally suitable for its appearance, its reflective brightness and its non-abrasive surface. With glass, brightness effects can be created that simply cannot be achieved with a glazed ceramic.

The Installation of Glass Tiling
The installation used primer, thin-bed mortar and grout mortar. The products, from the brand codex, met the pre-requisites for the bonding of glass, which generally has no absorbency properties, in guaranteeing long-term functionality and in fully meeting the criteria and requirements of durability and resistance to cleaning.

The priming of the special construction was with 'Fliesengrund', a solvent-free product that binds the upper sections of the substrate and is water-proof and water-repellent, so that the adhesive mortar does not lose its mixing water into the highly absorbent substrate. This protective- and bonding- agent is suitable as a primer to protect moisture-sensitive surfaces and to bind residual surface dust that can impair adhesion. As a neutral-odour bonding agent, it seals the pores of the surface, binds dust and protects from damaging water ingress to the substrate as well as too rapid absorption of the required mortar mixing liquid.

Floating-Buttering Method
Then the glass tiling was laid on a solid bed of trowelled mortar using the floating-buttering method. One advantage offered by the thin-bed method is the rapid installation. This is best achieved when the thin-bed mortar is applied to the substrate. In trowelling, ridges are formed into which the fluted backing of the glass tile can be firmly pressed (floating method). In the buttering method, the thin-bed mortar is applied to the back of the glass tile. Then the tile and mortar are laid using a light twisting movement and are pressed well down (buttering method). If, as with the poor absorbency of glass tiling, one has to rely on especially high adhesion, a combination of floating- and buttering- methods are used. Therefore, the thin-bed mortar is applied to the substrate and the tile backing. Fixing of the tile is achieved by bringing the two mortar layers together whilst they are still soft and plastic.

The thin-bed mortar used, Power Extraflex, has been developed specially for high demand areas and large format tiles. The dry powder mortar contains special cements, mineral aggregates and additives, has high flexibility and excellent pull- and shear- strength. It is waterproof as well as frost resistant and is suitable for adhesive bed thickness up to 10 millimetres.

The grey grout mortar, 'Brillant Flex' from codex, is suitable for fast, stress-reducing grouting even with glass tiles. Brillant Flex is used in particular in areas with high exposure to wetness and temperature changes and is suitable for joint widths from five to 20 millimetres on walls and floors. This rapid, hydraulic-setting grout mortar sets crack-free, water-impermeable and frost-resistant.

The Installation Company Fliesen Junck
The company Fliesen Junck from Berlin was awarded the work of both producing the substrate construction as well as installing the glass tiling.

Fliesen Junck Fachbaumarkt GmbH was founded over 30 years ago, then purely as an installations company. Today, it has 70 employees with 40 tile fixers in Berlin. Fliesen Junck sells and installs ceramic tiles and natural stone mainly in the local area. For end-users, a showroom has been established in the building trades market. In addition to the installation and wholesale services, Fliesen Junck has another branch of the business in the form of a workshop in which natural stone is cut to the requirements of customers and architects. 70 percent of the turnover is in installations in contract work. Reference projects of Fliesen Junck's work are seen all over Berlin. The company won the contract for the refurbishment of the Foreign Office in Berlin, with the renovation of all the toilet and sanitary areas.