Residential and commercial construction in Winterthur

Every summer half-year, the historic Hegi rice mill is still at work. Then the shavings fly in show mode and museum visitors watch as the water-powered saw cuts beams from tree trunks. Not far from the historic site on the Reismühle canal, atelier ww has realised a residential complex with 109 flats and around 1,500 m of commercial space at2 . The design, developed in dialogue with the urban design specialist group, was executed in accordance with the SIA Efficiency Path 2040 standard. In order to realise the mill-inspired façade quickly and sustainably, the formwork was fastened using REISSER RDS spacer screws.

Located between the Reismühle canal, Eulachpark and the old village centre of Hegi, the L-shaped complex is divided into five staggered building wings on Rümikerstrasse and a head-end building divided into two structures on Hegifeldstrasse. The four-storey ensemble with a staggered storey, which is connected by an underground car park with 90 parking spaces, thus adapts to the small-scale development of the village surroundings. At the same time, the additional façade areas created by the projections and recesses of the three- and four-storey buildings lined up next to each other allow for optimal lighting of the living spaces.

The site's pathways and garden design reflect the projecting and receding building wings and culminate in several communal and private outdoor seating areas. The commercially oriented head building in the north of the site is oriented towards the intersection and is set back here in favour of a small forecourt. All of the flats are arranged in an east-west direction. The ancillary rooms are located close to the stairwell, while the living spaces are orientated towards the garden. Each ground floor flat has access to its own garden, while the top floor flats have private roof terraces. The balcony construction for the units on the upper floors is a galvanised steel frame placed in front of the building, which stands out clearly from the building's pre-greyed wooden façade with its natural anodised aluminium external blinds and red fabric awnings.

Timber formwork held at a distance with RDS and screwed together more quickly

In keeping with the neighbouring sawmill, this uses vertically installed spruce formwork, which alternates between light and dark in the projections and recesses and is combined with light-coloured windows. In order to install them sustainably and as quickly as possible, the timber construction company worked with REISSER RDS spacer screws made of stainless steel A4. The fire protection-compliant material is required for invisible and inaccessible screw connections for rear-ventilated rainscreen façades.

The spacer screw, which has been tried and tested in Switzerland for 25 years but is still relatively unknown in Germany, is also equipped with two different threads at the head and tip, unlike conventional screws for the installation of rear-ventilated rainscreen cladding. The head thread holds the profile to be fixed (wood or aluminium) at a distance. The dowel thread is used for fastening in the substrate using plastic frame anchors for load transfer in tension and compression. The screw design enables large façade surfaces to be levelled and screwed together at high speed - a requirement that also significantly influenced the choice of fastener for the Reismühle residential complex.

Top efficiency thanks to '1-2 man' assembly

As the installation system with the REISSER RDS spacer screw basically enables a quick installation process due to the so-called "1-2 man installation", the building envelope - depending on the façade wall - could be installed quickly and to the highest quality with just one fitter or a maximum of two ximal fitters. One fitter first applied the façade insulation over the entire surface, inserted corresponding auxiliary brackets above and below the insulation and temporarily fixed the substructure for the outer skin with the REISSER RDS spacer screw, which is suitable for all commercially available insulation materials and profiles. The formwork was then attached to this substructure and precisely aligned using a laser. The continuous screw fastening was only carried out at the very end. The simplified fastening method requires fewer work steps overall, as the insulation material does not have to be cut out for the screw connections. This counteracts design errors and leads to considerable time and material savings, combined with easy installation and greater cost-effectiveness. And last but not least, the low thermal conductivity of the A4 material minimises heat loss via the screw connections with the REISSER RDS spacer screw