How do I form semi-exposed ceilings?

Glasroc F FireCase or Glasroc F MultiBoard and Gyproc Moisture Resistant (MR) grade boards (e.g. Gyproc FireLine MR) are suitable linings for semi-exposed ceilings providing the boards are protected from direct weathering and driving rain. Linings should be protected at the ceiling perimeter with a fascia deep enough to prevent rain being blown onto the board. However, it should be noted that Glasroc F FireCase, Glasroc F MultiBoard and Gyproc Moisture Resistant (MR) grade boards are unsuitable for use in areas subject to continuously damp or humid conditions.

For semi-exposed areas exposure to positive and negative air pressures (wind loading) should be evaluated by a structural engineer to assess a ceiling framework capable to provide suitable lining support. 

When finishing boards in sheltered, semi-exposed soffits, boards should be tape and jointed, rather than skimmed. This should be achieved using Gyproc jointing products as detailed in the White Book ‘Jointing’ section, here, and finished with a specialist protective paint system, supplied and specified by others.