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Structures in Building Culture

Crafting wood (2014)

Log cabin construction in Tuass and Münz, 2014

Drawing inspiration from traditional log cabin construction techniques from Scandinavia and the Alps, we spent ten days stacking wooden beams. The beam here is a building block, an element to be stacked. This method contrasts with traditional Dutch methods of building wooden structures, which are hierarchical and made up of various types of beam. For centuries we have used this method to build ships, farmhouses and roofs, all of them skeletal structures that are covered with brick, wooden planking or sheeting. ‘In constructing roofs and ships, the sequence of assembling the various components is of great importance, largely owing to the structural hierarchy of the components. Analogous to the human body, the keel is the spinal column, the trusses are the ribs, and the planks are the skin.’ (from Joinery 2012, connecting wood).

In log cabin construction, there is no hierarchy between components, since the wooden beams are both structure and façade cladding. The log cabin tradition originated with farmers who used the available material – stone and trees – to erect shelters for cattle and hay in the mountains. They stacked logs on a stone base to create simple structures. Using this system, two people could build a complete hut within a week, beginning on the ground and stacking slowly upwards. With the log cabin method, every tree trunk is equal. The most elaborate detail is the corner where two beams meet. For this corner joint, a number of solutions have been devised, among them the butt and pass, saddle notch, finger joints and dovetail. The detailing of the wood at the corners ensures that the beams fit together and that the walls are closed and sturdy.

During the quest to find our own log cabin construction methods, we were also immediately confronted with the corner detail. How are we going to turn the corner? How do we position a beam with respect to the beam below and the beam around the corner? Can we make it and build it? And what does it look like then? The search led to four principles for constructing four cabins. Each principle not only has logic of its own but also an unintended relationship with the log cabin tradition.

Tuass cabin 1
Münz cabin 1
Tuass cabin 2
Münz cabin 2

The reconstruction drawings were made by Daniël Bakker

A plank as module.  The basis of this principle is the conceptual idea to use one type of plank and minimize the number of steps. The construction of Tuass 1 is composed of horizontally and vertically stacked planks that are trimmed to exactly the right length. Alternate vertically stacked planks extend past the joint, creating an asymmetrical corner. This method is similar to the butt and pass joint, in which every second beam extends beyond the corner. It is probably one of the oldest log cabin construction methods and avoids complicated corner details. The end of one plank abuts the side of the next plank, eliminating the need for notches. There is no joint, but simply a stack.

The beauty of a corner.  The Tuass 2 corner detail has the refinement of a Japanese wooden joint. It’s an elaborate detail that requires lots of connections and notches. The construction consists of two beams alternating with a plank. The connections, notches in the beams, are visible. No beams or planks extend beyond the corner, and the corner is symmetrical. This method of construction most closely resembles the finger joint method. The notches are partly sawn out of the wood, and partly composed of smaller beams. Together, these components create the right form at the corner. The notched connections create a smooth surface that reads as a carefully composed furniture detail.

Prefabrication. Because of their desire to prefabricate the components for Münz 1, this group made a structure based on a standard notch as connecting detail. The beauty lies in its repetition and precision. The beams of adjoining walls are stacked alternately to form an open structure. Notches are clearly visible. Both walls extend past the corner, creating a symmetrical joint. This method of open stacking comes closest to the ‘saddle notch’ method that is commonly deployed when stacking untreated logs. The notches in both logs interlock with each other, creating a strong corner and eliminating the need for other means of connection.

An invisible detail. The idea for Münz 2 is based on the conceptual idea of making the corner joint invisible with a dovetail joint. The process is simple: all beams are equal in length and fitted with the same dovetail and notch. One of the two walls extends past the joint, creating an asymmetrical corner. Traditional log cabin construction features a number of dovetail principles in which the joint is visible at the corner of the two beams. In this case, however, the dovetail is applied in a remarkably hidden manner. This method calls for great precision and can only be fabricated using a milling machine. Different beam heights are used on either side of the corner, resulting in an unusual effect and enhancing the idea of an invisible corner.

The corner solution shows the skills and signature of the carpenter. The four groups formed their own ideas, which then led to a method of construction. The emphasis on particular aspects differed from group to group: from a conceptual idea about using materials and ordering, to a desire for efficient prefabrication and the pursuit of beauty. The three principles of Vitruvius – strength, beauty and utility – reached their own balance within each group. Ten days of drawing, measuring, sawing, milling, fitting and composing led to four unique building structures, each of which breathes new life into the log cabin tradition in a unique way.

Machiel Spaan
July 2015