Resisting fire spread from one building to another

The external envelope of a building should not provide a medium for undue fire spread to adjacent buildings or be readily ignited by fires in adjacent buildings. This intention can be met by constructing external walls so that all of the following are satisfied. a. The risk of ignition by an external source to the outside surface of the building is restricted. b. The amount of thermal radiation that falls on a neighbouring building from window openings and other unprotected areas in the building on fire is not enough to start a fire in the other building. c. Flame spread over the roof and/or fire penetration from external sources through the roof is restricted. The extent to which this is necessary depends on the use of the building and its position in relation to adjacent buildings and therefore the site boundary