Wood Magazine - Issue 1, 2016

Photo: Moelven Töreboda

Moelven Töreboda applies a post and beam approach for its in-house system, designated Trä8. This comprises glulam posts and beams, a stabilising system of glulam and LVL (Laminated Veneer Lumber) panels, plus floors and ceilings that use LVL beams and panels. Stability is ensured by box beam units made from glulam and LVL, filled with mineral wool insulation. The floor units are constructed from LVL panels with most of the veneer layers running lengthways and a small number running at 90 degrees. The panels are laid on LVL beams whose fibres run along their length. The exterior can be finished with curtain walls that are fitted outside or between the post and beam carcass. The structural design allows great freedom when it comes to window placement.
Photo: Derome

Derome is able to offer buildings of up to 6–7 storeys using surface units, with great scope for interesting floor plans. They build all the wooden frames industrially and transport the units to the construction site for quick and efficient assembly. The surface units comprise a wooden structural frame with insulation and a surface layer. The façade material can be adapted to the location. Derome will shortly be launching a new product in the form of modules for up to 4 storeys.
Photo: Martinsons

Martinsons uses cross laminated timber (CLT) in the floor and stabilising walls, and sometimes uses the post and beam system. The inside of the external walls is CLT, onto which insulation and the exterior façade are fitted. The floor structure comprises a CLT panel that is bonded to glulam beams with an underlying flanged beam in glulam, plus insulation. Separated from the top of the floor structure is a frame of 220 millimetre wooden beams that supports the ceiling below. Insulation is inserted between the beams. The thickness of the floor structure is around 0.5 metres. The CLT units are 12 metres long and 1.2 metres wide. The floor units rest on the CLT wall units. The maximum window width is 2 metres without reinforcement. The openings in the façade should be spread symmetrically along the vertical axis so that the outer walls can provide sufficient stability.
Photo: Lindbäcks Bygg

Lindbäcks Bygg uses wooden box units with an internal ceiling height of 2.5 metres and dimensions of max 3.9 x 8.4 metres. The maximum width is determined by road transport restrictions. The outer walls of the modules are load-bearing, with the ceiling and floor suspended from the walls. The modules are designed so that a room can be made up of two or more modules. One module can also contain two or more smaller rooms, such as a bathroom, corridor or wardrobe. If a module wall is less than 4.4 metres, openings are compensated for with glulam beams, and if a wall is wider steel joists are used. The walls in the modules are stud walls. This means that openings in façades and load-bearing walls should be positioned symmetrically along the vertical axis for stability reasons, which can limit the window options. On the other hand, it is an example of traditional façade design in wooden buildings.

Wooden high-rises apply modern technology

by Carl Michael Johannesson

Today, it is technically possible to design ever taller structures in wood, and that creates considerable freedom. The limits of what is possible have moved forward, not least in residential developments. Long gone are the ruthless efficiencies of the Million Programme, which produced homes that later generations saw as monotonous, despite their high technical and functional quality.

THE RIGHT TECHNIQUES, coupled with regulatory changes, now make it possible to build in wood over many floors. Practically any design can be manufactured and erected, almost no matter how complex it is. In the end, price, running costs and future care and maintenance requirements determine the appearance and design choices.

All over Sweden there are companies that make and build homes in wood. Whether these are site-built, prefabricated or modular, the companies have know-how amassed over generations, which now takes in CLT, sometimes in combination with several other materials in hybrid structures.

There are several companies in the Swedish market that manufacture carcasses and components for multi-storey wooden buildings. The various construction systems have their differences, but they also have many things in common. Several include traditional stud walls, they have thick floor structures between the apartments and in some cases they are subject to the limitations of the timber when it comes to free spans. The installation solutions in floors and shafts are pre-prepared, while sound and fire proofing insulation between the apartments is taken care of horizontally and vertically.

The advantage of buildings constructed using CLT and post and beam systems is that they offer greater flexibility regarding room layouts and uninterrupted spans. They also offer certain benefits with regard to impact sound insulation. Some designs incorporate a cast concrete slab of 50 millimetres or more, which allows the total thickness of the floor structure to be cut by around 100 millimetres while retaining the same impact sound insulation. The thickness of the floor structure affects not only the overall height, but also the design of the façade and the building’s integration with the surrounding built environment.

COMPARED WITH MOST OTHER MATERIALS, wood has more functional properties. It provides thermal insulation, resists wind and weather, stands up to traction and compression forces and is easy to handle and shape. The environmental characteristics are also a plus. The positive properties are overwhelming, but only if the material is used properly. In addition, the material is easy to amend and work with, paint and surface treat, plus it has a finished surface ready for treatment immediately after being sawn and planed. The work put into the surface through care and maintenance is reflected over the whole lifetime of the building. Weather, erosion from the sun’s rays, grain, texture and patina help give a wooden façade character and beauty over a very long time.

Wood’s geometric aspects are reflected many times over in carcasses and façades, and this contributes to a feeling that is difficult to quantify, but still significant.

With increasingly cost-effective solutions, there is a risk that building in wood will be anonymised, without embracing the material’s possibilities for detailing and well crafted meetings between structural elements and façade features. Unfortunately, it is sometimes the case that surface decoration has had to compensate for excessive cutting of corners.

The construction system is often compared with the industrial manufacture of cars, for example, where specialisation is far-reaching and plant costs amount to hundreds of millions, or more, with development costs taking up a large chunk of turnover. Competition there is tough, and survival in the market depends on renewing and adapting the product to the end customer. Within certain industrial segments, companies undergo renewal over a cycle of 3 to 5 years. A failed product is a threat even to the biggest company. A successful product, on the other hand, has a value all of its own that makes the owner happy.

ONE CAN ONLY HOPE that the demand for renewal will come from the clients themselves. ‘Tried and tested’ was the order of the day in the 1970s and 1980s, when new technical solutions created damp and maintenance issues. Since then, industrial advances have led to better, more sustainable and more energy-efficient constructions. Those who draw comparisons with vehicle manufacturers are right to do so. But in contrast to a car, which mainly makes the owner happy, an attractive building can make more than the owner and the users happy, while also helping to raise the value and status of a neighbourhood or district.