The provisions of this section have effect with respect to the terms of advances under section 435.
The advance, together with the interest on it, shall be secured by a mortgage of the land concerned; and an advance shall not be made unless the estate proposed to be mortgaged is either—
The amount of the principal of the advance shall not exceed the value of the mortgage security or, as the case may be the value which it is estimated the mortgaged security will bear when the construction, conversion, alteration, enlargement, repair or improvement has been carried out; and the advance shall not be made except after a valuation duly made on behalf of the authority.
Where the advance is for any of the purposes specified in section 435(1)(b) and (c) and (1A) (construction, conversion, alteration, enlargement, repair or improvement) it may be made by instalments from time to time as the works progress.
The mortgage deed shall provide—
but subject to section 441 (waiver or reduction of payments in case of property requiring repair or improvement) and to section 446(1)(b) (assistance for first time buyers: part of loan interest-free for up to five years).
The mortgage deed shall also provide that, notwithstanding the provisions referred to in subsection (5), the balance for the time being unpaid—