Hands, shoe prints, tools and entire trees – Doka is making its mark on this new build in the city's famous Národní Street. All exactly to specification. The fair-faced concrete core of the monolithic building in the heart of Prague is hallmarked by artistry cast in concrete, from the basement levels up to the top floor.
The exceptional design by architects Ing. Arch. Stanislav Fiala/Fiala + Němec s.r.o reflects the diversity intrinsic to concrete as a material. Pure, unpretentious aesthetics and artistic traits alike necessitate precision formwork engineering.
Ceilings and walls on every level feature varying inserts, including for example impressions of stones and tiles, ropes, fabrics and tools. Doka met these peculiar architectural challenges primarily by deploying its Framax Xlife and Dokaflex formwork, both renowned for the top-class appearance of the finished concrete.
But made-to-measure special formwork by the Doka Pre-assembly Service also features largely on this build. All in all, 30,750 m2 of Doka formwork are in use.
In order to produce a specific pattern in the finished concrete, in certain places the Doka formwork sheeting is removed and replaced with OSB, cement excelsior boards or planed boards. The imprints are created by fixing actual objects as positives to the face of the formwork sheeting. The prepared formwork is sprayed with release agent and the objects are removed as soon as the formwork has been stripped.
Framed formwork Framax Xlife is the main product for forming the walls of the Palác národní. The sturdy steel frame and the Xlife sheet ensure excellent concreting results, with a regular joint pattern from the panel size-grid. High resistance to scratches and vibrator damage is a big advantage of the plastic-enhanced surface of the Xlife sheet. The finish helps prevent splintering at nail-holes and allows the sheets to be cleaned with high-pressure spray cleaners.
The ceilings of the Palác národní feature unique castings in relief. The fast, hand-set Dokaflex system is ideal for these jobsite parameters. The beams of the Dokaflex system telescope, so the formwork can be fitted neatly to columns and walls. The free choice of sheeting makes this system perfect for widely differing sets of requirements. Formwork sheets 3-SO are much used on the Palác národní build. Made of spruce, this 3-ply sheet is of the high standard of workmanship and wood quality that extend its suitability to include fair-faced concrete finishes. It is durable and dimensionally very stable, and the all-round edging strip makes it easy to clean.
Concrete cast in colour
Colour highlights are another feature of the concrete walls in the Palác národní. Added before the fresh concrete leaves the plant, the colour is thoroughly mixed in during transport to the jobsite. When it comes to forming, it is very important to ensure that each batch of coloured concrete sets before the next layer can be poured. Otherwise they could mix and “colour noise” could result.
The safe way to success
Safety comes first on every jobsite. So on the Palác národní build, lead contractor Terracon relies on the Edge protection system XP from Doka. The system consists of uprights combinable with all forms of barrier and railing (wooden boards, galvanised gratings, etc.). This system of fall protection is universal, so it can be used for formwork, stairways or at the edges of buildings. "We supplemented the columns with XP Protective grating, which we consider a great bonus. Not only is it easy to mount but in real terms its use is safe. A situation where the men on the site would borrow a plank from the handrail and leave a gap in it, just because they need wood, can't arise", notes site manager Miroslav Mrázek from Terracon. Another benefit is that this system simplifies jobsite logistics – the Edge protection system XP takes up about one third less space for transport and storage.