The invention relates to a composite floor beam (30) for use in construction. The composite floor beam (30) comprises an upper part (32) made from a first material extending substantially along the length of the beam and a lower part (34) made from a second material such as metal extending substantially along the length of the beam, the upper part (32) comprises an upper surface (40) and a lower surface (42). The lower part (34) comprises an upper surface (51) and a lower surface (52). The upper surface (40) of the upper part (32) is designed to be arranged horizontally to support a floor above. The upper surface (40) of the upper part (32) is parallel to the lower surface (52) of the lower part (34). The lower surface (52) of the lower part (34) is designed to be arranged horizontally for attachment to a ceiling below. The lower surface (42) of the upper part (32) and the upper surface (51) of the lower part (34) define apertures (36) between them for cabling and/or piping and/or other utilities. The apertures (36) pass from a first side of the beam to a second side of the beam. The direction of the apertures (36) passing from the first side (38) to the second side (39) being transverse to the direction of the length of the beam (30).