A mezzanine for storage is not designed like an office area or like a space carrying heavy machinery. The use determines the loads and affects the sections, the spacing of the beams, the connections, the deck and the anchoring.
Where it is required, the technical solution has to rest on a study by a qualified engineer, and not on an experienced eye.
The use has to be known before the choice of sections begins. Imposed loads are not a matter of the fabricator's judgement: they are classified to EN 1991-1-1 by category of use — dwelling, office, assembly area, storage — and the values come from the Greek National Annex. A storage mezzanine has nothing in common with a sleeping one, neither in its sections nor in its anchors. Beyond strength, what is examined is deflection, the connection to the existing structure — the load ends up in a wall, a column or a floor that has to accept it — and access together with escape.