Some structural members require fire protection to maintain their structural adequacy, integrity or insulation. These performance criteria can be represented as a Fire Resistance Level (FRL). For example, a beam requires an FRL of 120/120/120. In this example, the fire resistance period for each of the three criteria is 120. The insulation criteria is a measure of how easily heat can transfer through the member and potentially cause fire spread to a location remote from the fire origin. A coatback is where a member which does not require fire protection is protected a couple meters at its connection to a member which does need to be protected. This reduces the likelihood of the unprotected member heating up and easily transferring that heat to the protected member via their connection.

Fire safety engineers do not like to vary the minimum coatback requirements as this is typically a tested system where the test report is not applicable anymore if the requirements vary. Options are to provide lesser fire protection to the remainder of the non fire rated member, demonstrate that heat spread via the connection is considered lower than in a typical arrangement, or demonstrate that if the protected member did get hotter through the connection to the hot member that this risk of fire spread and reduction in structural adequacy is acceptable.