The materials used in the construction of an eco-house are key to its green credentials. There are various green options available, but it is important to consider loadbearing issues when making your decision. Ask your supplier to identify which type of block is suitable for exterior and interior loadbearing walls, as some may be loadbearing, but still unsuitable in an exterior wall. One of the best ways to help the environment is to source materials locally; transport costs are reduced and you may be able to check production methods and the sustainability of sources.

Strengthening the structure
Laying a block flat, rather than on its edge, can make a significant difference to a wall’s strength. Some compressed earth blocks, for example, have a minimum compressive strength of 435psi on their edge, rising to 2,465psi when they are laid flat. On their edge, most loadbearing concrete blocks have a minimum compressive strength of 1,015psi.

Combining conventional bricks and blocks with green bricks and blocks in the same structure is not recommended. While conventional bricks and concrete blocks are often combined, green blocks should be used consistently. In addition, as green blocks can vary in size dramatically, complete walls should be built with cut blocks rather than alternating sizes.

Types of Green Building Materials

Clay brick
This is an unfired clay brick, commonly used in cobwork. They can be used for non-loadbearing walls or infills in lumber-frame constructions.

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Hemp block
The base material of these blocks consists of fibers from the hemp plant mixed with sand and lime.

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Compressed earth block
To make this block, clay, aggregates and water are pressed into a mold and dried. Traditional blocks of this nature, such as adobe blocks, were sun-dried, but modern versions are mechanically compressed.

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Compressed earth block
To make this block, clay, aggregates and water are pressed into a mold and dried. Traditional blocks of this nature, such as adobe blocks, were sun-dried, but modern versions are mechanically compressed.

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Extruded earth block
This block is molded, or "extruded," into a continuous length in a machine, and then cut into smaller blocks.

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Cob block
This sun-dried block is made from mud held together by straw, and is normally used to repair existing cob buildings.

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Clay plasterboard block
As the name suggests, this type of block has been made from clay and recycled drywall. It uses a thin-joint mortar system and may be laid on its edge or on the flat for greater loadbearing strength.

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Fired aerated clay block
Although these bricks are fired, their mode of manufacture uses a relatively small amount of energy, lowering their "embodied" carbon dioxide content.

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Straw bale
Made from the dry stalks of cereal plants, such as barley and wheat, straw is an excellent insulator, and consequently a good material for blocks.

Courtesy of DK - Do It Yourself Home Improvement © 2009 Dorling Kindersley Limited