Section 3280.307 - [Effective 3/17/2025] Resistance to elements and use(a) Exterior coverings shall be of moisture and weather resistive materials attached with corrosion resistant fasteners to resist wind, snow and rain. Metal coverings and exposed metal structural members shall be of corrosion resistant materials or shall be protected to resist corrosion. All joints between portions of the exterior covering shall be designed, and assembled to protect against the infiltration of air and water, except for any designed ventilation of wall or roof cavity.(b) Joints between dissimilar materials and joints between exterior coverings and frames of openings shall be protected with a compatible sealant suitable to resist infiltration of air or water.(c) Where adjoining materials or assemblies of materials are of such nature that separation can occur due to expansion, contraction, wind loads or other loads induced by erection or transportation, sealants shall be of a type that maintains protection against infiltration or penetration by air, moisture or vermin.(d) Exterior surfaces shall be sealed to resist the entrance of rodents.(e) Multi-section and attached manufactured homes (see subpart K of this part) are not required to comply with the factory installation of weather-resistant exterior finishes for those areas left open for field connection of the sections provided the following conditions are satisfied:(1) Temporary weather protection for exposed, unprotected construction is provided in accordance with methods to be included in the approved design.(2) Methods for on-site completion and finishing of these elements are included in the approved design.(3) Complete installation instructions and the required materials for finishing these elements are provided.(f) The exterior wall envelope must be designed and constructed in a manner that prevents the accumulation of water within the wall assembly by providing a Water Resistive Barrier (WRB) behind the exterior cladding and a means of draining water that enters the assembly.40 FR 58752, Dec. 18, 1975, as amended at 86 FR 2520 , Jan. 12, 2021 86 FR 2520 , 3/15/2021; 89 FR 75749 , 3/17/2025