The outer wall components are resistant to fire from the inside for more than 90 minutes, due to the inbuilt 84 mm thick sacrificial layers, which burn at 0.9 mm per minute under optimal ventilation conditions. The sacrificial layers delay the fire reaching the load-bearing core layer by approximately 93 minutes.
The conclusion was that wood is three to five times more resistant to fire than concrete or bricks. A thick wooden block does not burn, but only becomes charred on the surface. Wood’s fantastic static properties are also retained much longer at extremely high temperatures in comparison with reinforced concrete structures, for example.
On the outer side, the solid timber façade component has board panels with a thickness
of 29 mm, inlaid and dowelled with the two soft wood fibreboards (Gutex Multiplex-top), each 22 mm thick. The fire performance of the soft wood fibreboards according to DIN EN 13501-1 corresponds to class E. The nominal bulk density of Gutex Multiplex-top is approximately 200 kg/m3.
As part of the IBA Hamburg, the “WOODCUBE” was intended take on a clear structural form and act as a prototype. This gave rise to the distinct cube shape, which ensured a high recall value. The building’s cubature is enhanced by irregularly spaced, freely overhanging balconies. These are designed in such a way as to give the impression that they swing out of the basic shape.
Possibility of Conversion
Due to the large floor spans, almost every type of room layout can be achieved within the building. Every floor features different types of apartments. As there are no load-bearing walls, room structures can be changed at any time. Some of the apartments are also set up in such a way that, if required, they can be made completely accessible without major alteration work.
Above the basement, which is a waterproof concrete tank, almost all of the load-bearing construction components are made of timber elements, with the exception of the staircase core. The basement contains space for storing bicycles and technical and supply rooms, along with a laundry room and storage spaces for the apartments.
Large windows that run the width of the balcony and smaller square, or rectangular windows that seem to be arranged without reference to one another, break up the façade. The vertical openings for the building services installations are in ducts on the eastern and western outer walls. The bathrooms and kitchens are arranged around these ducts. Overall, the cubic form of the building makes it very compact.
The apartments on the west side of the second and third floors were joined together vertically to form a maisonette. The fourth floor, however, is designed as a closed unit. Each apartment has at least one balcony on a corner of the building and oriented east, south, or west. The roof, which is covered with a photovoltaic unit, is not accessible.
As far as I can trace it, all the well preserved buildings were built with slow and traditional methods. The minimum requirement was to cut the trees in winter while the moon is waning. Even better are the days just before the New Moon in Capricorn.
The 'Abbrandlerhoefe' however, those farms which needed to be rebuilt hastily after a fire and couldn't possibly be built that way. Harvesting hay happens in midsummer when the heat causes the fermentation of hay and its combustion. Therefore building wood needed to be logged in the hot part of the year and often didn't even have time to dry properly. This does influence the quality and longevity of the building.
A project of this kind and needed to be planned carefully and was worked on over a period of time. All the accumulated experience of farmers, talented carpenters and trades people contributed to a lasting building. Due to this tradition and attitude of our ancestors, we now have buildings hundreds of years old and still functioning.
Time was scarce too. Large farmer families, including the farmhands and animals, needed to have a new roof above their heads before the next cold winter would descend from the glaciers and surrounding mountains. Over many centuries, building a farm in a very short time was only an exemption due to a catastrophe. A farm was built for many generations to come, not just the grand kids.
Living and surviving in this harsh and steep alpine environment has always kept these people closely knit. After such a disaster, neighbors would work together and help the owners to log the trees and swiftly start working on the new building which was then called the 'Abbrandlerhof'.
This sometimes causes the hay to ignite all by itself and is called spontaneous combustion. Quite a few stately and very old farm houses have turned to ash and rubble in this way. For most of the 'Salzburger' alpine farms, there is an existing privilege. In the case of a burned down farm, the farmer is allowed to cut trees for building materials in the state forest free of charge.
In the hot and humid midsummer days when thunderstorms are brewing, farmers often have to rush and bring in the still moist hay before a downpour. This way the hay might not get soaked in the rain, however a much more dangerous threat to the hay barn and farm buildings is lurking: A bale of hay only half dry starts fermenting and in just a few short hours develops an incredible internal heat.
'Abbrandlerhoefe' - farms which have been rebuilt after a fire
This is the name given to farms in the area of the 'Salzburger Land' which were rebuilt after a fire. Bringing in the harvested hay, especially the second cut which is called the 'grummet', always poses a certain risk and sleepless nights for the farmer.
The resulting success is obvious - I never forgot the prank and I still remember why this wooden fireplace never caught fire! The reason was: the particular larch trees which were used to build it were cut at a very specific time according to the phase of the moon. I found this very intriguing and practical at the same time.
The penitential pilgrimage afterwards led me from the village police to my mother, from there to my father, to the teacher and to the principal. At every stop, I experienced another interaction which was meant to deter my boyish brain from ever playing with matches again.
The black chimney flue made from larch wood boards went through the ceiling, the 2 bedrooms upstairs passing through and beyond the shingled roof. This old farm house was perched like an eagle's nest upon the highest rocks above a steep meadow, close to my home town 'Bruck am Grossglockner'.
An old wooden chimney made a huge impression on me during my childhood. This strange object was located in a 400 year old farmhouse in the Austrian alps and belonged to friends of ours that farmed this mountain side. The charred wooden chimney started above an open fireplace at the main floor of the house built from wooden beams.
Only some of its surface will be charred as a result. When the source of fire disappears, the trunk stops burning as well. For wood to burn well, it must be cut into small pieces and surrounded by air. Today, Dr. Thoma's firm builds certified firewalls made of wood for industrial needs.
The same treatment of a reinforced concrete wall would have caused the temperature on the opposing side rise to 600° even after 20-30 minutes and everything would start to burn. Because of the heat, the concrete begins to crack in layers and release the rebar rods which then melt. It may seem unbelievable, but even a thick tree trunk thrown into the fire will often remain unburned, while the fire eventually fades and dies out.
After 122 minutes, there was a strange sound. It turned out that the tank ran out of oil. Following this incident, the institute carried out the test at its own expense and in the end, Dr. Thoma received a F180 certificate. It turned out that after three hours of treating a Holz100 wall with a 1000 ° flame, the temperature on its other side rose only by 1.8° C.
Dr. Thoma insisted, and the manager replied, irritated: “Listen, I have been working at the Institute for many years, and I have tested everything one could test in the timber industry. You should be glad if it can even withstand the F30 test. It will definitely not last any longer.” Finally, Dr. Thoma offered to pay for every minute of the test and the manager agreed, shook his head, and started the test.
Dr. Thoma had initially claimed that although made of wood, Holz100 was a completely different structure and asked for them to examine how long the wall would last beyond F30. In response, the manager looked at Dr. Thoma as if he were an idiot and replied, “I said F30”.
Holz100 Canada Inc.