39. When an appeal is made to the Board under section 7(1)(b) F65 [ , section 7(1)(d) or section 7(1)(e) ] of the Act, the Board in considering such appeal shall—

(a) be restricted to considering the extent to which the design of the building complies with the requirements of Part B F66 [ or Part M ] of the Second Schedule to the Building Regulations, and

(b) have due regard to any dispensation from, or relaxation of, a requirement of Building Regulations granted under Section 4 or 5of the act in respect of, or which is relevant to, such building.