Zero Freeboard

Most of you will already be aware of the commonly desired design of having an alfresco or portico at the same finished floor level as the dwelling, however what doesn’t appear to be common knowledge is the fact that this isn’t necessarily a deemed-to-satisfy solution due to the requirements of the BCA (Volume 2) for an alfresco, porch and other external paved surfaces adjacent to the building must be at least 50mm below the finished floor level of the dwelling and slope away 25mm over first 1m to prevent water entering the building. For permeable external surfaces, the finished floor level of the dwelling is to be a minimum of 100mm above finished ground level.

There is potentially a number of ways in which this can be achieved however will likely need to be considered as part of an Alternative Solution prior to the building permit approval – we recommend discussing this with your design team to come up with a solution in order to meet the performance requirements of the BCA and this can then be presented as part of the building permit application.

Some examples of a suitable ‘zero freeboard’ design could be the incorporation of a strip drain system at the door sill and also where the raised external surface meets the external wall (as the penetration of surface water / moisture into the dwelling also needs to be addressed at this location – not just at the door sill).