Building portion having a wall; at least one strip-shaped supporting and insulating element which is arranged to the side of the wall, wherein the supporting and insulating element has a supporting part having a first lateral surface running in the longitudinal direction and a second lateral surface running in the longitudinal direction, which runs substantially perpendicularly to the first lateral surface, wherein the supporting part is formed from a load-bearing material, wherein the supporting part has a first leg which comprises the first lateral surface and an inner lateral surface opposite to the first lateral surface, and has a second leg which is connected to the first leg and projects from the first leg at an angle, and wherein the supporting and insulating element further comprises a reinforcing element made of metal or fibre-reinforced plastic which extends at least in the region of a reinforcing surface of the supporting part running in the longitudinal direction and is connected to the supporting part by means of at least one fastening means; and a window frame which is supported on the second lateral surface of the supporting part of the at least one supporting and insulating element; wherein at least one fastening element for fastening the window frame to the supporting part is received in at least one through-bore which runs through a portion of the reinforcing element and, from the region of the inner lateral surface of the second leg to the second lateral surface, through the second leg of the supporting part, wherein the portion of the reinforcing element is arranged in the region of the inner lateral surface of the second leg; and wherein the first lateral surface of the supporting part bears against the wall, and the supporting part is fastened to the wall by means of at least one fastening element; characterized in that the reinforcing element is substantially L-shaped in form in cross section; and the at least one fastening element for fastening the supporting part to the wall is received in at least one through-bore of the reinforcing element that runs through a first leg of the reinforcing element and is aligned with a through-bore in the first leg of the supporting part. a wall; at least one strip-shaped supporting and insulating element which is arranged to the side of the wall, wherein the supporting and insulating element has a supporting part having a first lateral surface running in the longitudinal direction and a second lateral surface running in the longitudinal direction, which runs substantially perpendicularly to the first lateral surface, wherein the supporting part is formed from a load-bearing material, wherein the supporting part has a first leg which comprises the first lateral surface and an inner lateral surface opposite to the first lateral surface, and has a second leg which is connected to the first leg and projects from the first leg at an angle, and wherein the supporting and insulating element further comprises a reinforcing element made of metal or fibre-reinforced plastic which extends at least in the region of a reinforcing surface of the supporting part running in the longitudinal direction and is connected to the supporting part by means of at least one fastening means; and a window frame which is supported on the second lateral surface of the supporting part of the at least one supporting and insulating element; wherein at least one fastening element for fastening the window frame to the supporting part is received in at least one through-bore which runs through a portion of the reinforcing element and, from the region of the inner lateral surface of the second leg to the second lateral surface, through the second leg of the supporting part, wherein the portion of the reinforcing element is arranged in the region of the inner lateral surface of the second leg; and wherein the first lateral surface of the supporting part bears against the wall, and the supporting part is fastened to the wall by means of at least one fastening element; characterized in that the reinforcing element is substantially L-shaped in form in cross section; and the at least one fastening element for fastening the supporting part to the wall is received in at least one through-bore of the reinforcing element that runs through a first leg of the reinforcing element and is aligned with a through-bore in the first leg of the supporting part.