Building in existing fabric conserves resources, saves energy, and reduces carbon emissions - good reasons to choose conversion over new build. Yet there is another, less tangible dimension: time. With additions and adaptations, patina and cracks, it leaves its mark and stores memories in the buildings. To carry these stories forward requires sensitivity to materials, spaces, and histories. Deciding what remains and what is replaced demands careful judgment.

Some interventions are so discreet that only trained eyes notice them, often compared by architects to the restoration of a classic car. Others are more radical: ceiling panels titled and set diagonally into a room, or large atriums cut into the existing architecture. At times, we may need to rethink our ingrained aesthetics and ask whether materials with a problematic reputation - such as fibre cement panels (Eternit) - can still be used, or whether cut edges might be left uncovered.

With time as a fourth dimension, building becomes a dialogue between past, present, and future. The projects in this issue of DETAIL magazine work with and on existing structures and cast a special light on this theme.

Building in existing fabric conserves resources, saves energy, and reduces carbon emissions - good reasons to choose conversion over new build. Yet there is another, less tangible dimension: time. With additions and adaptations, patina and cracks, it leaves its mark and stores memories in the buildings. To carry these stories forward requires sensitivity to materials, spaces, and histories. Deciding what remains and what is replaced demands careful judgment.

Some interventions are so discreet that only trained eyes notice them, often compared by architects to the restoration of a classic car. Others are more radical: ceiling panels titled and set diagonally into a room, or large atriums cut into the existing architecture. At times, we may need to rethink our ingrained aesthetics and ask whether materials with a problematic reputation - such as fibre cement panels (Eternit) - can still be used, or whether cut edges might be left uncovered.

With time as a fourth dimension, building becomes a dialogue between past, present, and future. The projects in this issue of DETAIL magazine work with and on existing structures and cast a special light on this theme.