Review of the CUT technique

Abstract

Bio-based and ecological buildings are gaining global importance, with straw bale constructions as one of the possible choices in Europe. Straw bale buildings are classified into load-bearing, non-load-bearing, and hybrid techniques. Load-bearing and non-load-bearing methods have been studied extensively in past decades whilst hybrid methods, such as CUT (Cells Under Tension) techniques have been somewhat neglected, despite its significant potential for advancing sustainable building practices. This master thesis presents a comprehensive review of the CUT techniques, a hybrid methods of straw bale building, which are used by approximately 50 builders and architects in Europe and South America, and more than a few hundred of buildings have been erected since 1995. Twenty builders and architects working with CUT techniques answered survey and analysis of their knowledge was performed to form the basis of this thesis The thesis also presents aspects of the CUT techniques such as CUT method modifications, mould growth analysis with the VTT model, Life Cycle Assessment, and a list of building details. By providing a comprehensive overview of the CUT technique, this research aims to highlight its significance in the context of ecological building practices and the findings of the thesis aim to contribute to the builders and architects working with straw bales and the CUT technique.

Popular Abstract

The CUT (Cell Under Tension) technique is a specific combination of straw bales, light timber frame construction, and plaster material. Together, these materials form a load-bearing, extremely well-insulated, ecological, healthy, and affordable building system.
The ability of each of used material is used to its maximum in the CUT technique. This helps to save resources but also to make the building very accessible and efficient. The walls of these houses are very simple, consisting only of three materials. Firstly, it is the straw bales – an excellent insulation and partly load-bearing material. Secondly, it is a timber structure made from very thin posts and battens. The timber structure transports some of the loads, but also holds the bales in place. The last material in the wall is earthen plaster, which is directly applied to the surfaces of the straw bales. The plaster gives the building its final rigidity. All of these materials can be either supplied or usually found locally a couple of kilometers from the building site.
The CUT technique is used mostly among self-builders and small companies across Europe and many houses were built since 1995, being happily used until today by many people. Unfortunately, the structural properties of this technique are not accepted by many building authorities in Europe. The technique relies on the capacity of the earthen plaster to transport loads, which might not be allowed. Several building professionals saw the potential of the CUT technique and decided to use some principles of the CUT technique in their projects, therefore, the CUT technique was modified. An outdoor or indoor layer of plaster was replaced by material that can legally take the loads (sheathing boards or planks), and the dimensions of the posts were increased. After these changes, the wooden part of the construction was sufficiently load-bearing.
Other CUT technique modifications emerged because the builders wanted to use the CUT technique for different purposes like wrapping old and new buildings, or to create organic shapes and forms, or building CUT walls that are not load-bearing in combination with Post and Beam wooden structures.
Several conclusions on the CUT technique and its modifications were drawn based on the survey responses, literature review, site visits, and interviews. The calculation showed that the environmental impact of the CUT walls is minimal compared to other commonly used building systems and that the walls are mould-safe according to a mathematical model.

• author: Podmolik, Josef
• supervisor: Paulien Strandberg; Herbert Gruber
• organization: Department of Building and Environmental Technology; Division of Energy and Building Design
• alternative title: Analysing Modifications, Performance, and Professional Practices of the CUT techniques
• course: AEBM01 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Straw bale buildings, Hybrid techniques, CUT construction, Modified CUT, LCA, Clay plaster, Mould Index
• language: English
• id: 9162802
• date added to LUP: 2024-06-13 07:59:04
• date last changed: 2024-06-13 07:59:04