Recycled materials in construction: types, pros and examples

Construction is one of the industries that produces the most waste – from demolished buildings, offcuts, packaging and unused materials. Yet much of it is perfectly fit for a new life.

Recycled and reclaimed materials are no longer just for experimental pavilions. We increasingly see them in homes, offices and restaurants – sometimes for environmental reasons, sometimes for the character they bring. Here is what you need to know before including them in your project.

What are recycled building materials?

They are materials made from processed waste, or elements from old buildings that are used again. It is important to distinguish between two things:

• Recycling – the waste is processed into a new raw material: concrete is crushed into aggregate, metal is melted down, glass is ground.
• Reuse – the element is taken in almost the same form: old bricks, timber beams, doors, parquet, tiles, basins, light fittings.

To these a third, newer idea can be added – design for disassembly. The building is designed so that its elements can be taken apart and reused at the end of its life: with bolted rather than welded connections, dry-laid construction, modular dimensions and clear documentation of the materials.

From an environmental point of view, reuse is usually the more valuable option, because it takes less energy for processing.

Which materials can be recycled or reused?

Almost every major building material has a second-life option.

• Concrete – crushed concrete is used as a sub-base for roads and paving and for backfill, and, with controlled quality, as aggregate in new concrete.
• Steel and metals – metals can be melted down again and again without losing their properties; steel sections can also be reused directly.
• Bricks – old solid bricks are cleaned of mortar and laid again; they are much sought after for interior walls and façades with character.
• Timber – beams, boards and parquet from old buildings become floors, cladding, furniture and worktops.
• Glass – processed into glass wool, foam glass, tiles and decorative paving.
• Plastic – used to make insulation materials, profiles, decking and tiles.
• Rubber – old tyres are turned into surfacing for playgrounds and sports facilities.

What are the pros and cons?

The main advantage is less waste and fewer raw materials; the main disadvantage is that quality and availability are harder to predict.

Pros

• Less waste going to landfill.
• Less extraction of new raw materials – sand, gravel, timber, ore.
• Less embodied energy – especially with direct reuse.
• Character – old bricks and timber have a patina that new materials cannot convincingly imitate.
• History – material from the family's old house built into the new home carries meaning.

Cons

• Inconsistent quality – every batch is different and needs checking.
• Limited quantities – large, uniform batches are hard to find.
• Extra labour – cleaning, sorting and processing.
• Certification – structural elements require evidence of their properties.
• Hidden risks – old materials may contain harmful substances, such as old paints or asbestos products, which require special handling.

What are the best-known examples around the world?

A number of projects have become benchmarks for what is possible.

• BedZED, London – a housing development in Beddington designed by the architect Bill Dunster, using reclaimed steel elements and locally sourced materials. It was one of the first large-scale eco-housing developments in the UK.
• EcoARK, Taipei – an exhibition pavilion whose walls are built from panels made of recycled plastic bottles. Designed by the Taiwanese company Miniwiz, it became a symbol of the idea that waste can be architecture.
• Resource Rows, Copenhagen – a housing complex by Lendager in which whole panels of brickwork were cut from old buildings and built into the façades of the new ones.

How to use recycled materials in your own project

The easiest place to start is with non-structural elements – cladding, floors, furniture, decoration – and to decide on this at the very start of the design process. Here is a sequence that works:

1. Take stock of what you have – if you are demolishing or renovating an old house, list the bricks, beams, doors, slabs and parquet that could be kept.
2. Decide where you will use them – a feature wall, flooring, cladding, furniture, garden paving.
3. Check their condition – damp, rot, cracks, traces of old paint or harmful substances.
4. Consult a structural engineer – anything load-bearing requires calculations and proven properties.
5. Find suppliers – dealers in reclaimed bricks and timber, construction waste yards, listings for salvaged materials.
6. Plan the logistics – cleaning, storage and transport take time and space.
7. Build them into the design – old elements often come in non-standard sizes, and the design must adapt to them, not the other way round.

What should you bear in mind in Bulgaria?

In Bulgaria the market for reclaimed materials is still largely informal, but old bricks, roof tiles, timber beams and stone slabs from village houses have long been sought after for renovations and new holiday homes. Recycled concrete and asphalt are used mainly in road construction.

Where a material has a structural role or must meet fire safety and energy efficiency requirements, it needs the relevant declarations of conformity. For decorative and finishing purposes there is far more freedom. It is best to discuss these choices with your architect at the concept design stage, not once the materials are already on site.

If you are planning a demolition, consider careful dismantling rather than rapid demolition – that way more materials remain fit for reuse.

Our approach at DARCH Projects

When we work on the renovation of existing buildings or on a new home replacing an old house, we suggest which elements are worth keeping and how to integrate them into the new architectural design. Often it is the old brick or beam that turns out to be the most memorable detail.

Frequently asked questions

Can old bricks be used for a new house?

Yes, especially for cladding, interior feature walls, boundary walls and garden paving. The bricks are cleaned of old mortar and checked for cracks and crumbling. If they are to carry loads, a structural engineer's assessment is needed, because the properties of old bricks may be unknown. For decorative purposes they are an excellent choice thanks to their colour and texture.

Is recycled concrete strong?

Crushed concrete is a reliable material for road sub-bases, backfill and paving. As aggregate in new concrete it can be used with controlled quality and in line with the relevant standards, usually replacing part of the natural gravel. For the structural elements of a building, the decision rests with the structural engineer and must be backed by testing.

Are recycled building materials cheaper?

Not always. Some reclaimed materials, such as old bricks or timber beams, can cost more than new ones because of the manual cleaning, sorting and demand for them. Others, such as crushed concrete for backfill, are usually more economical. Often the benefit lies in the character and the reduction in waste rather than necessarily in a lower price.

What risks do old building materials carry?

Old materials may contain harmful substances – for example lead-based paints or asbestos products, once used in roofing and pipes. Timber may be affected by fungi or insects, while bricks and stone may have absorbed salts and moisture. That is why every material should be inspected carefully and, if in doubt, checked by a specialist.