(1)Subject to the provisions of this section, the gross value of any small post-1918 dwelling-house which is neither a local authority or housing association dwelling-house nor a flat or maisonette shall be five per cent. of the hypothetical 1938 cost of construction of the dwelling-house plus five per cent. of the value of the site on the first day of April, nineteen hundred and forty-nine, estimated on the basis—
(a)that all buildings have been removed therefrom ;
(b)that there is no impediment (whether of a legal nature or not) to the use of the site for the construction thereon of a dwelling-house of the same general character and dimensions as the existing dwelling-house and with foundations occupying the whole, or, at the option of the builder, any part of, the ground occupied by the buildings of the existing dwelling-house ; and
(c)that any permission required by any statutory provision for that use of the site will be forthcoming unconditionally, and in particular, in the case of a permission under the enactments relating to town and country planning, will be forthcoming without the imposition of any development charge.
(2)If the state of repair or amenities of the dwelling-house are not as good as those of the majority of comparable dwelling-houses in the locality, being dwelling-houses to which this section applies, the gross value of the dwelling-house shall be the amount ascertained under the preceding provisions of this section diminished by such amount as may be just.