Sections R405, Foundation Drainage, and R405.12, Concrete or Masonry Foundations, of the 2021 International Residential Code are hereby amended to read:

Provisions shall be made for the control and drainage of surface or standing water around buildings by installation of an approved rain drain system that is tightlined to an approved public storm water conveyance system.

Adequate provisions shall be made to ensure that under-floor spaces remain free of running or standing water by the installation of drains or by installing structural fill material that lifts the foundation to level that is above the existing water table. At a minimum, such drains shall be installed around the perimeter of the building at the footings.

Additional drains may be required in the under-floor space. The drainpipes shall be sufficient size to adequately convey water to an approved public conveyance system but shall be a minimum size of four inches. Provisions shall be made to prevent the drainage system from becoming blocked by soil. The Building Official may waive the provisions of this section when soils appear to adequately drain the site and no water will stand or run under the building and the project is in compliance with adopted stormwater requirements.