R405.1

Section R405.1 is titled 'Concrete or masonry foundations' and covers the requirements for subsoil drains around foundations that enclose habitable space. The purpose of this section is to control subsoil water around the foundation to prevent it from entering the dwelling; and to alleviate hydrostatic pressure against the wall to prevent structural failure.

The model shows a section of a foundation system with the subsoil drainage portion highlighted. This system uses a perforated pipe with a sock filter which is surrounded by gravel.