19 Building materials not made from metal, especially doors and windows including roof windows, roofs or in the form prefabricated glass roofs, roofing riles, window sills, building materials (not made from metal) as parts of roof trusses, fittings and non-electrical locks, ventilation and smoke exhaust flaps, folding shutters, rolling shutters, external blinds (nor made from metal), concrete slabs, construction materials made from concrete, building materials (not made from metal) building materials (not made from metal) for use in chimney construction (not made from metal), roof dormers, roofing tiles, pan tiles, roof gutters, roofing materials, prefabricated roof elements, building materials (not made from metal) as parts of, concrete ceilings, roofing paper and paper skeins, roof membranes with and without hard boarding, air and vapour barriers, wall membranes, separation layers, all of the aforementioned not made from metal, used for building purposes