ICF stands for Insulating Concrete Formwork. Hollow insulation blocks or panels are stacked to form the walls, reinforced, and then filled with concrete, leaving the insulation permanently in place on both faces of the finished wall. The result is a well-insulated, airtight structural wall.
In ICF construction the formwork is not stripped after the concrete cures — it stays as the insulation layer. This produces a continuous insulated envelope with a solid concrete core, which gives good thermal performance, high airtightness potential and substantial structural strength.
Internal finishes are usually applied to the insulation with plasterboard, and external finishes are typically render or a rainscreen cladding. Service routing has to be planned because chasing into the insulation is done in a controlled way rather than cutting into masonry.