Rule C: Alterations and extensions
2. In the case of alterations not involving any extension of a building—
(a)the plans and sections required by item 5 of Rule B of the alterations and of the building so far as affected by the alterations, so far as necessary to establish whether the proposals comply with these regulations; and
(b)a key plan showing the position of the site when it is not sufficiently identifiable from such plans.