Introduction

For centuries, wood and timber have been used as very important building materials in many countries. However, at the same time fires posed a major threat to cities, towns and other urban areas comprising a large number of wooden buildings. After a century with strict regulations regarding use of wood in urban areas, this is now changing due to several reasons:

• Implementation of performance based building and fire regulations
• Regarding of wood as a sustainable and environmental friendly material
• Introduction of fire safety engineering tools
• Introduction and combination of new passive and active fire safety measures

At NTNU, a number of MSc thesis projects have been carried out during the last years, focusing on various aspects of fire safety of wooden buildings. These projects cover historical buildings and areas as well as design and engineering of modern wooden buildings.

Fire safety of old wooden buildings
MSc Project Tommy Skålvoll

The MSc project was carried out in connection to a project regarding fire safety of Røros, an old wooden mining town on the UNESCO World Heritage List. The study comprised a survey of risks for fire initiation and spread in old wooden buildings. Several fire safety strategies and measures may be applied in order to avoid fire initiation and spread, covering fire prevention as well as fire protection issues.

Application of a Fire Risk Index method for multi-storey wooden buildings showed that implementation of some measures could reduce the Risk Index value from 3.57 to 2.62 for a specific building.

New building adjacent to old wooden buildings
MSc project Bente Veiåker Engmo

The study covered a new block of flats being placed adjacent to blocks of old wooden buildings in the city centre of Trondheim. Alternative conditions and measures regarding fire safety were examined. Methods to estimate the actual fire risk and possible fire conditions included national standards and methods for calculation of heat radiation.

The major risk was fire spread due to heat radiation, and especially to the window areas. A combination of technical and administrative measures were considered to be sufficient to prevent fire spread from the actual neighbour building at a distance of approximately 4 meters.

Multi-storey wooden buildings
MSc projects Torfinn Heier and Ronny Hatterud

A proposed three-storey wooden block of flats with a floor area of about 1200 m2 and 10 flats on each floor was studied. It was found that use of available analytical and calculation methods would cause some alternative design solutions of fire protection measures that would increase the fire safety of the block. A detailed fire safety concept was developed for the specific building, showing that it is possible to design rather big wooden buildings mainly based on the prescribed solutions as given in the Guide to the Building Regulation.

Fire safety aspects of a new four-storey wooden block of flats with a floor area of about 530 m2 and with 5 flats in each floor were studied. The block could not be designed according to the prescriptive rules as given in the Guide to the Building Regulation. The fire safety of the block was evaluated by use of both qualitative and quantitative analyses, as given in national standards, specific guidelines and a Fire Risk Index method.

The fire safety of the four-storey block was compared to the fire safety of a block constructed from concrete and steel, and without residential sprinklers, by use of a Fire Risk Index method. The Risk Index values turned out to be about similar for the two blocks.

• For old wooden buildings in urban areas, fire safety can be improved by various fire prevention and fire protection measures, including technical as well as administrative measures.
• For new buildings to be placed adjacent to old wooden buildings, special precautions have to be taken to obtain a sufficient fire safety. The major risk is caused by radiation.
• Performance based building regulations, fire safety engineering tools, new applications of wood materials and structures and fire protection measures have made it possible to design new multi-storey wooden buildings, also for urban areas.

Acknowledgements

The authors want to express sincere thanks to the MSc students Tommy Skålvoll, Bente Veiåker Engmo, Torfinn Heier and Ronny Hatterud. Further, thanks to the Wood Programme at Innovation Norway for sponsoring the work and to engineering companies advising the students during their project work.