R905.1.1

Section 905.1.1 is titled 'Underlayment' and covers requirements for roof coverings. The mandate for underlayment for certain types of roof coverings to conform to applicable standards, for underlayment complying with specific standards to be labeled as such, to be labeled with classification if applicable, and to be applied and attached in accordance with cross-referenced tables in this code is established. The purpose of this section is to prevent water damage to the building. This section has 3 exceptions which allow for alternative underlayment arrangements. The purpose for the exceptions is to allow for alternative underlayment arrangements that adequately protect the building from water damage.

The model shows a partial cutaway view of an asphalt shingle roof covering assembly which explodes and reassembles to show the installation order of components. The underlayment is highlighted.