Unfired Clay Bricks: Exploring an Old and New Option

Unfired clay bricks have been used for millennia, despite challenges related to strength and durability. Today, they are gaining renewed interest for their potential to drastically reduce CO₂ emissions.

A recent Environmental Product Declaration (EPD) from a Danish brick factory suggests that eliminating the firing process could reduce CO₂ emissions by up to 90%, depending on the energy source. Since 2021, DTU Construct and DTU Sustain have led a project—sponsored by the Capital Region—aimed at modernizing and optimizing the use of unfired clay as a viable construction material. This initiative has already resulted in a demonstration wall built using extruded clay blocks.

A major challenge remains: unfired clay bricks are not currently included in CEN standards, creating regulatory and practical barriers to their adoption in construction. To address this, the project has expanded its scope to include documentation of the load-bearing capacity of masonry made from unfired bricks and clay mortar. Additionally, collaboration has been established with a parallel project (Leralliancen) exploring indoor walls constructed with unfired clay blocks.

In spring 2024, DTU conducted tests on masonry test walls, mini-walls, and smaller specimens of unfired clay bricks and clay mortars produced from glacier clay. These tests aimed to validate a proposed calculation model for the vertical load-bearing capacity of unfired clay masonry. The results so far are highly promising.