A local housing authority may by resolution designate as a class buildings in their district each of which consists of or includes one or more dwellings if it appears to them that—
Subsection (1) does not apply to a building in a class designated under section 528 (designation by Secretary of State); but a building does not cease to be included in a class designated under this section by virtue of its inclusion in a class designated under that section.
A dwelling which is, or is included in, a building in a class so designated is referred to in this Part as a "defective dwelling"; and in this Part, in relation to such a dwelling—
A designation shall describe the qualifying defect and specify—
A designation may not describe a designated class by reference to the area (other than the authority's district) in which the buildings concerned are situated; but a designated class may be so described that within the authority's district there is only one building in the class.
Any question arising as to whether a building is or was at any time in a class designated under this section shall be determined by the local housing authority concerned.