Building and siteworksmust be arrangedso that surfacewater from a storm with an annual exceedance probability of 1% (i.e. a 1 in 100 year storm) does not enter into a building.

A storm with an annual exceedance probability of 5% (1 in 20 year storm) has a less intense flow of water than a storm with an annual exceedance probability of 1% (1 in 100 year storm), which is what the subject building must be protected from.

It is considered more important to prevent water entering a building than it is to prevent water entering a neighbouring allotment or property.

The limitations contain several exemptions to F1P2 These are based on the belief that the use and safety levels of the exempted buildings will not be significantly diminished by surface water entering them.

Limitation (a) regarding Class 7 and Class 8 buildings refers only to such buildings which, in a particular case, do not exhibit any need for compliance with F1P2. Such buildings must be considered on a case-by-case basis. However, it is the responsibility of a building proponent to satisfy the appropriate authority that the exemption should apply. The structures like garages, tool sheds, and sanitary compartments forming part of a building used for other purposes are also exempted, provided they do not contribute to the weatherproofing of another part of a building that needs to be weatherproofed. Lastly, open spectator stands and open-deck carparks are not required to comply with this provisions.