bunk bedmeans any bed having a sleeping surface which, or any part (including the under-surface) of which, would be 800 millimetres or more vertically above any horizontal surface on which the bed were placed in such a position as would be usual for the purpose of enabling a person to sleep on the bed, and references to “height” in relation to a bunk bed or any part of one shall be construed accordingly;
permissible gapmeans — (a) in relation to a gap in the sleeping surface of a bunk bed, a gap of not more than 75 millimetres;