Rapidly growing interest in contemporary timber buildings and engineered wood products like CLT (Cross Laminated Timber) striving to address the ecological emergency suggests raising a question on where will all the additional wood needed to fulfill this mass-transition come from? At the same time the way we are dealing with waste timber highly disregards its unique qualities and potential for high-value use. This paper begins with a review of the existing literature to identify the knowledge gap on the advancements made in regards to design tools and innovative building components using waste wood in architecture applications. Through identification and assessment of the ‘leaks’ of waste in timber value chain the focus was given to the waste components coming from sawmilling processes. This theoretical approach gave basis to practice-based prototypes using ‘’offcuts’’ collected at a small-scale sawmill and inventoried based on photogrammetry technology. According to the geometrical data collected a digital twin library was generated to support the most efficient use of the material. The prototypes reference directly to CLT construction and investigate how the function of a structural panel could be achieved using waste wood. Additionally, previously discarded characteristics of the collected material were explored to serve in an architectural context. In conclusion the paper highlights the potential to make way for waste wood in sustainable timber construction and opens up questions for further research necessary to implement this concept towards commercial application.
2.1 Case Studies
Digital Structures, MIT
Nordic Waste Wood for Good
The Voxel Quarantine Cabin
Moving towards net zero plan is accompanied by many sustainability legislations to help become carbon-neutral by 20501 . Starting in 2022 the new law mandates that new buildings in France are built at least from 50% timber or other natural materials2 . Those and many other policies must be implemented to tackle climate change, however, this raises the question of where will all the additional wood come from?
Overall consumption of primary processed wood products is expected to grow 37 percent by 2050 in a business-as-usual scenario and even 8 additional percent more in a bioeconomy scenario considering top modern wood products – mass timber and man made cellulose fibers – as a substitute for leading, non-renewable materials of the past decades – concrete and steel3. Therefore we must very carefully study and perhaps restructure the forestry value Chain.
The relevance of protecting the world’s forests, together with its expansion is rooted in the fact that they play a key role in preserving the climate. Not only as a provider of sustainable building material but as an organism, which hosts the ecological process needed for biodiversity and life on earth to thrive. One of the most important transactions happening in biology is the carbon dioxide exchange and the forests play a key role in it.
This study is divided into two parts, analysis of existing literature and research gaps in the light of wood waste qualities and their potential in architecture applications. Secondly, developing a framework for production of CLT panels, which is studied to find new opportunities to integrate sawmill timber waste material for new waste timber building components. The methodology for this research is to address three objectives of the investigation: the impact on Timber Waste Streams, the fabrication of the architectural component (CLT panel) and the geometry (architectural application). Following this investigation technique the project can evolve with the feedback provided by each method, finally becoming an informed prototype design.
3.1 Material Analysis
This section presents the computational design and prototyping for working with a library of waste components (offcuts) to create secondary timber CLT panels, which can be used as an exterior and interior structural component.
The offcut material was sourced at Valldaura Labs sawmilling station. The leftover material comes from CLT panels production from 2020. The half-round offcuts collected at the site come from Pinus radiata pine species and were harvested at site in a random pick order, less than a kilometer away from the mill. It is important to recognize that this material was not stored with an intention to further use it in the future. It had been exposed to direct sun and rain.
The first step for analyzing the available waste stock integrates several tools and processes:
3D reality capture based on photogrammetry and geometric reconstruction that helps to gain information of the components, regardless their irregularities in shape and size. Material Digitization allows for capturing real world spatial data into computer systems. This data must be further analyzed to extract the information valuable to the experiment. In this research 3D scanning data collection had following goals:
- To obtain three-dimentional geometric data to reconstruct the offcut components as a mesh in a 3d software and to learn about their dimensions (primarily varying thickness and lengths).
- To obtain two-dimensional curve outline data to allow it to be used in the algorithm.
To compare the results and estimate the best techonology to be used for collecting all the necessary data measurements from reality were taken and compared with the 3D model result from three different softwares. The result closest to the real component dimension were achieved by Reality Scan application, using photogrammetry. Following that this became the main tool for creating the Digital Library of Offcuts.
3.2 Digital Library
Within this master thesis introducing digital tools allowed for collecting detailed measurements data of the collected material, but also allowed for extracting various geometrical forms of this data. Three databases of the offcut geometries were established. First, photographic data was collected. Each of the components was photographed from different angles, resulting in an average number of photographs between 60 to 85. Later, a point cloud meshing and texturing was achieved giving a result of 3D textured models. An analysis and further geometrical deconstruction of this database provided the information on irregularities in dimensions through the length and width of the components. Those complex geometries were then converted into simplified meshes, in order to reduce their file size and to allow further geometrical analysis.
3.3 Computational Design
Several experiments were committed to find out the optimal number of pieces needed in the Digital Library for receiving satisfying results to produce a long lasting panel with a continued surface coverage, additionally with the minimum material loss due to the processing. These tests were run on the first of the variables, where the Panel Size was given and the Coverage Area and the Waste created were calculated. The result showed that the optimal number of items starts already with 15 items in the library, giving a panel coverage of 85% of the desired panel size. Which later on in the fabrication tests showed high surface continuity of the outer offcut layer of the panel. However, the higher number of Items in the library, the least waste is Created.
The role of the algorithm as a tool for CLT Offcut panels fabrication is to have greater control over the irregular geometries of the material and to minimize the waste produced during carpentry processing needed to use the waste components as a high value use product. The architecture of the script allows for panel design which relates to its future purpose and design strategy.
3.4 Prototype and Design
This master thesis focuses on the architectural applications that relate directly to today’s building practice. The prototypes reflect common building elements, where the goal is to represent current wood applications and their function in buildings. They reference to CLT construction with the goal to investigate how the function of a structural wall could be achieved using waste wood and through analyzing the previously discarded characteristics of the collected material explore additional properties, which could serve in an architectural context, for instance as a façade layer.
Additionally, the exploration of folding Shading Structure application proposed in the last chapter raised a question on the connection detail between the panels. Therefore, the prototypes also explore the joinery proposed in the design and the process of Digital Fabrication. Finally, a full scale Demonstrator in a form of a furniture was designed, following the same structural principles as the Shading Structure and fed with results of the Flexible Panel Size Variable, where the final form is directly related to the material available in the Digital Library.
The main goals of taking a step into physical prototypes were:
- To demonstrate the feasibility of use of irregularly shaped sawmill offcuts on the outer layer in the production of CLT panels .
- To test the results of the scan resolution in relation to measurements from reality.
4. Design and Fabrication
Following the material qualities exploration and the material analysis conducted through Prototype 01 it was crucial to implement those findings into a bigger scale architectural language that could refer to the potential life extension of the waste components and their future in becoming a high-use value product. To showcase the potential of the Offcut Panel to serve as both structural and façade component of a building a folding structure is explored. This self-supporting structural skin serves simultaneously as a building envelope, which relates to the recognized quality of the grain continuity of the Offcuts and their potential to become an exposed exterior layer.
To take advantage of the nesting algorithm and the Digital Library of 16 Items collected and scanned for the purpose of this research the first step was to propose a smaller furniture scale structure, which could be supplied from the Digital Library of 16 items.
The Furniture is a teaching tool, with a gradient of results for solving emerging design and fabrication challenges. This architectural experiment puts an emphasis on the Flexible Panel Size Algorithm Variable and explores the way how this type of structure could be addressed by the Digital Library and the available Material Stock. In other words – it explores how an architectural form could be found on the basis of the characteristics (in this case dimensional) of the material available and at the same time find a design which can benefit from the embedded material qualities. The Panel Size X (Width) and Y (Length) are the inputs for the Dimension available for the form.
The first step was to (using the Flexible Panel Size Variable and nesting algorithm) create a set of Panels to be used as the furniture form driver. The parameters set for this process were the Maximum size of the available CLT press at Valldaura Labs – where the physical experiments were conducted (250 cm x 117.5 cm) and later the Thickness and Panel Coverage % Match was set to provide the highest result possible.
Out of 16 Items available in the Digital Library 5 panels varying in size were created.
There are already many possibilities explored in the field of timber structures proposing various ways of connections and joineries for timber plates, such as metal rods, metal plate connections, dowels, press-fit joineries etc. Already explored in CLT construction – digital fabrication with CNC offers a wide range of possibilities to tailor the joinery of mass timber panels and opens possibilities for timber-to-timber connections.
This research prioritises wood joineries using 3-axis CNC router as a fabrication method. After the final form of the Furniture experiment was established, the joinery was designed – with a goal to maintain continuous exterior offcut surface and to be able to control the varying angles between the panels.
For the sake of working in 3D environment the Digital Panels were transformed into simplified boxes – which translate to the highest thickness dimension of the panels.
In order to verify physical feasibility of the ‘’fold’’ and the proposed workflow the design was taken into 1:1 scale prototype. This experiment puts special focus on testing the joinery proposed for maintaining a continuous folded surface and the fabrication strategy for merging material geometrical individuality and design efficiency. Additionally, a conclusion on material behavior during fabrication is drawn.
Drawing from experience from Prototype 01, which explored the method of Offcut CLT panels production steps, two panels resulting from the Flexible Panel Size Variable (Figure 43) were produced for a second phase of experiments, this time exploring the Furniture fold design. Previously observed fabrication difficulties opened a new research question on how to address the recognized material difficulties and provide a responsive fabrication workflow. Two connections, both of different angles, were tested for achieving more results related to material loss during fabrication and for further surface continuity and angle fitness tests. Each of the joints received a different cutting strategy. A new tool for collecting the fabrication data was introduced, having in mind that the machine settings resulted in playing a key role in achieving satisfying results.
Another step into improving the material – customized fabrication settings was to recognize that the layer of the offcut is the one more sensitive to the milling process. To address that the strategy was extended into a 3 processes, where the first 4 cm of cut-to size lamellas were milled following Roughing Strategy (5 mm cut depth) in order to speed up the processing and beginning the Re- Roughing Strategy was introduced at the height of the Offcut Layer. This strategy allowed for a major improvement in results.
The objectives of the research were to investigate the synergies between the recognized qualities of the waste material and architectural application to develop a building component in a form of a CLT panel, with a goal to extend their life-span and provide new high-quality purpose which could benefit the Timber Value Chain for carbon storage. Through the Final Prototype the research covered the material testing for fabrication methods and achieved a method for producing Offcut CLT panels. To adopt those findings and apply to a scalable design a shading structure is proposed.
CLT construction is mainly represented by orthogonal grid designs, which refer to the material as a final supply for an already detailed design. Folded structures are less explored, specifically using mass timber elements. The staring point is a simple algorithmic folded structure design, where the folded geometry gives possibility for self-supporting large span structure, which simultaneously serves as a skin layer. Through the ‘’fold’’ this proposal investigates the potential of a ‘’waterproof timber’’ where the Offcut Components serve as the exterior layer and placing panels in an angle allows the exterior water flow. Previously explored Thickness Matching and Surface Continuity is crucial for this type of design. Beyond that the Flexible Panel Size Variable continues to be the design driver, therefore the proposal aims to be a result of the available material stock.
The potential observed during the Folded Structure Exploration (Figure X.) was the fact that it is composed from independent ‘’stripes’’ of panels. This observation gave a way to directly connect the dimensions of the structure to the Digital Library Stock, which informs the form. Each of the ‘’stripes’’ correspond to one panel in the Panel Stock. The X and Y dimensions of the panelized form refer to the X and Y dimension of the material available. Learning from the results of the fabrication which indicated various material quality issues, which might be caused by not proper way of storing the waste components – the offcuts collected were laying around sawmilling station at Valldaura Labs, exposed to direct sun and rain. The Offcut Shelter is used as a roofing structure for storing waste components for future use, with the goal to create an efficient drying environment. For wood to dry evenly, avoiding drying-caused defects like cracks, certain weather conditions are to be favored and some to be avoided. Through various climatic analysis the structure finds the best position to create protection from direct sun and to open itself to winds coming mostly from the north.
5. Results and Discussion
The research examined the use of offcut sawmilling wood waste as a building component, specifically focusing on half-round offcuts for top layer of mass timber structural panels. The study used 3D scanning and digital library tool to create a database of the waste components, and developed algorithms for panel design that allowed for optimized and controlled usage of the offcut components. Two different design variables were explored, one with a fixed panel size and the other with a flexible panel size. Prototype panels were fabricated and tested, with results showing high accuracy thickness match for surface continuity. However, issues with material loss and surface continuity were encountered during the joinery fabrication process, which relates directly to the state of the material collected. Overall, the research highlights the importance of digital fabrication strategies and further exploration of waste material processing in relation to defects and proposes an architectural application of shading folded structure, which tackles the issue of previously not fulfilled wood drying conditions (use) and the potential of recognized qualities of the waste material to serve as a structural and façade building component.
Author: Agnieszka Szklarczyk
Thesis Supervisor: Michael Salka
Program: MAEBB 02 2021-23