Design for disassembly

The concept of design for disassembly means that a construction is designed in a way that allows the structure to be disassembled, and the materials can be subsequently used for another construction. The construction should be separable without damaging the materials used. Design for disassembly can be incorporated into construction projects with bricks to a much greater extent than is currently done.

The purpose of this article and task is to provide you with insight into the advantages of building with bricks where design for disassembly is considered, and to equip you with the ability to choose a mortar that facilitates the disassembly and reuse of materials in the future.

Teacher's guide:

4. Brick_EN.pdf

Bricks

Bricks made of clay are well-known for their durability, and with proper maintenance, brick constructions can last for many years. When dealing with a material like brick, which has a relatively significant impact on the environment, it is essential that constructions are designed with a focus on the possibility of disassembly and reuse at a later stage.

In construction, design for disassembly is a new term that has grown alongside the desire to reduce the construction sector's environmental impact.

For many years, mortars have been used in bricklaying that allows the disassembly of the masonry, cleaning the bricks, and reusing them.

Murbrokker inden rensning

The duration of the exercise:

Approximately 45 minutes.

However, examples of mortar for bricklaying have emerged where the adhesion to the stones is so strong that the stones cannot be separated from each other. And the stones that can be separated cannot be cleaned because the mortar's adhesion to the stones is too high.

Masonry with these mortars leaves no option but to crush the bricks for recycling. It is regrettable to use a refined material like bricks, for example, as road fill, considering that there are alternative materials with far less environmental impact.

However, there are examples where bricks laid with hard mortars can be reused differently. The hardness of the mortar allows the masonry to be cut into module joints, which can later be reinserted. This type of reuse is relatively resource-intensive and, therefore, not as widespread at present.

Photo: Rasmus Hjortshøj - Architect: Lendager

People in the industry believe that it is especially the new functional mortars that make cleaning of bricks impossible. This is mainly due to the high binder content in functional mortars. Despite the lower potential for reuse, strong functional mortars have many advantages. They are very robust, making it easier for engineers to ensure the durability of the construction. The mortars have a quick setting time, meaning they are easier to use during periods of moderate frost. This results in fewer weather-related delays and a more efficient construction process. Functional mortars can also become part of the solution in the future. It only requires manufacturers to recognize the need for mortars to be disassembled in the long run while retaining their other beneficial properties.

Working with bricks

In the planning of brickwork, design for disassembly can be incorporated. This ensures the greatest possible potential for reuse in the long run. It requires questioning the material composition so that the mortar used for bricklaying has the necessary strength but is not stronger than necessary. This way, it ensures both the desired durability of the construction and the potential for material reuse.

Roof tiles

Clay roof tiles have several favorable characteristics, including a long lifespan, sturdy durability, excellent adaptability, and, notably, significant potential for reuse. These qualities make clay roof tiles a high-quality product.

Tegltage

There has likely been little consideration given to incorporating design for disassembly into many existing roof structures where clay roof tiles have been used. Nevertheless, the majority of roof constructions using clay roof tiles are designed in a way that allows for the separation of structures, enabling the tiles to be removed intact and reused elsewhere.

The favorable possibilities arise from the fact that most roof constructions with clay roof tiles are assembled in ways that make them relatively easy to disassemble. The clay roof tiles are fastened to a batten substrate with steel ties that can be easily loosened. Ridge tiles may be either masonry-bonded or screwed on. In cases where ridge tiles are mortared together, relatively weak lime mortars are often used, making them easy to clean. In cases where ridge tiles are screwed together, they can be unscrewed for disassembly.

Tagsten

During dismantling, it is essential to handle the roof tiles appropriately. The tiles should be carefully removed, bundled up for easy handling, transportation, and laying on a new roof. This should be considered from the outset of the dismantling process to avoid costly procedures.

Tagsten på paller

An untapped potential

Unfortunately, most bricks are not reused. This is likely because it is not economically advantageous, given the current practices. When brick roof tiles are dismantled, they are typically thrown down through waste chutes, causing them to break. Subsequently, the broken tiles can only be used for recycling. Much of the crushed brick is used as road fill or as a base for green roofs.

Tagsten klar til knus

Examples

Bricks that cannot be reused due to mortar choice

The four images above clearly show that the bricks are well bonded together, making them impossible to clean and reuse.

Example of roof tiles being reused

Tagsten

The roof tiles have been removed to replace the underlayment. In this process, the battens are also replaced before reinstalling the old roof tiles.

Example: roof tiles for reuse bundled up

It is an advantage to clean the roof tiles before they are taken down. Once the roof tiles have been removed, they should be bundled for easy handling and laying out in the next roofing project.

Task - choice of mortar

In this task, you need to consider how to combine bricks with different mortars. The purpose of the task is to give you insight into which mortars can be used for specific exposure classes.

Your task is to find mortars for bricklaying that can be used for each exposure class. The selected mortars should be as weak as possible while still meeting the requirements for the exposure class. This ensures the best starting point for later disassembly and reuse.

Which bricklaying mortar can be used in the following exposure classes?

  1. MX1
  2. MX2.1
  3. MX2.2
  4. MX3.1
  5. MX3.2
  6. MX4 *
  7. MX5 *


* MX4 and MX5 are additional classes that cannot stand alone.

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