(1)  A provision of the Building Regulations does not apply to any building work –

(a) for which a building permit is granted before the provision commences; or

(b) if the building surveyor for the work certifies in writing that substantial progress was made on the design of the work before the commencement of the provision.

(2)  Subsection (1) does not apply if the building surveyor and the owner of premises where building work is to be performed agree that a provision of the Building Regulations applies to the building work.

(3)  Nothing in this section prevents a person from complying with a provision of the Building Regulations that is not an applicable provision by virtue of this section.