Over the past decade the field of designing buildings for recycling has become of increasing interest to researchers investigating approaches to designing sustainable buildings. More recently the research has focussed on producing practical guidance for building designers interested in designing sustainable buildings. The guidelines and principles for designing buildings for dismantling, reuse and recycling developed in the last five years focus on two main areas:

1 the process of removal of building elements and materials from building structure

2 the requirements for reprocessing of building elements and materials to enable reintegration in a new building.

DISMANTLEABILITY
To facilitate the removal of elements and materials from a building, these have to be designed to be technically capable to be removed with as little effort and as quickly as possible. A quick and effortless dismantling process will reduce costs of dismantling, which will then begin to compete with the cost of a standard demolition process and become more economically attractive. Effective dismantling is desirable whether the building elements are to be reused, recycled or down cycled. To achieve building designs that can be efficiently dismantled the following points should be considered.

• INFORMATION - Provide As Built drawings and Maintenance Log including identification of points of disassembly, component and material and identify materials and points of disassembly on elements.
• ACCESS - Provide easy and safe access to building element and fixings with minimal machinery requirements.
• DISMANTLING PROCESS - Simplify fixing systems and enable removal by means of small hand tools and handheld electrical tools avoiding specialist plant. Use mechanical rather than chemical fixing. Provide realistic tolerances for assembly and disassembly. Design joints and components to withstand dismantling process.
• HAZARDS - Make components sized and of a weight to suit the means of handling and provide means of handling and locating. Avoid toxic materials.
• TIME - Minimise number of parts, fixings and types of fixings and allow for parallel disassembly.

REUSE, RECYCLING AND DOWNCYCLING
Once removed from the building, elements have to be reprocessed to enable their reuse or recycling. The nature and amount of preparation work required will depend on the characteristics of the elements and the designated use. Taking into account that reusing elements provides the greatest environmental benefits, the following recommendations aim to maximise the ability for the materials and elements to be reused, but also aim to ensure that once the element can no longer be reused it is capable of being recycled.

• REPROCESSING - Use materials that require minimal reworking, avoid non-recyclable materials such as composite materials and treatments and secondary finishes to materials that complicate reprocessing. Minimise the number of different types of components and ensure inseparable subassemblies are from the same material and components of different materials are easy to separate. Flexible installation options included.
• HAZARDS - Minimise toxic content, if toxic content is unavoidable ensure the ability to release it in a controlled manner. Make components sized and of a weight to suit the means of handling and provide means of handling and locating.
• DURABILITY - Use sturdy and avoid fragile material. Design joints and components to withstand repeated use.
• INFORMATION - Provide identification of material and component types. Provide product details and installation instructions.