24.—(1) Subject to paragraph (2), in-situ foamed urea formaldehyde shall not be used in the erection, structural alteration or extension of a building.
(2) In-situ foamed urea formaldehyde may be used for filling the cavity of a cavity wall having an inner leaf constructed of bricks or blocks, provided that it is—
(a)suitable for such an application; and
(b)satisfactorily installed.