Abstract: A composite foam and concrete building component (1) for forming panels such as walls and roofs includes a central core (4) of structural concrete as a framework of spaced posts (6) and beam (7) structures, around blocks (8) of rigid, closed cell foam material such as expandable polystyrene (EPS) foam or expanded poly-lactid acid (PLA) foam. The core is straddled by front and back layers (2,3) of low density, cellular concrete, thus encapsulating the foam blocks. Cellular concrete plugs (14) can extend through the foam blocks to bond the layers together. The component can be formed by separately pouring the structural and cellular concrete without significantly altering the formwork.