Plasterboard etc at ceiling level is, like the roof covering, considered as long term.
The allowance for storage in the roof void at ceiling level is also treated as an ever-present, long term load.
As these will also be present throughout the building's life loads applied by water tanks are treated as long term loads.
The design allowances for loadings due to snow on the roof are treated as medium term loads, i.e. these loads will not be present at all times, but will affect the roof structure only for a period of weeks or months at a time.
6.Man Load on Rafter and Ceiling:
Where this is applicable, this load is treated as a short term load, ie this load will be present within the structure for a period of minutes or hours only.
Always considered for design, the loadings due to wind are treated as very short term loads. These loads will be present on the structure for a period of minutes or seconds only. The above loadings cover the most usual types of load carried by trussed rafters. Other loads may be present within the roof in special circumstances These may include air conditioning equipment, patient hoists, climbing ropes etc and must be allowed for in the design, in the appropriate load case.