An architectural feature of a building on a medium street must not project beyond the street alignment unless the architectural feature—
(a) projects no more than 600 mm horizontally beyond the street alignment; and
(b) is at least—
(i) 5 m in height above any part of the street that may be used by a motor vehicle; or
(ii) 2.7 m in height above the level of the street in any other case; and
(c) is constructed from non-combustible material.