Title 16 - Buildings and Construction

16.110 Residential Code for One- & Two-Family Dwellings

16.110.R405.1

Section R405.1 of the International Residential Code for One- and Two-Family Dwellings is hereby amended to read as follows:

R405.1 Concrete or Masonry Foundations.

Drains shall be provided around all concrete or masonry foundations that retain earth and enclose habitable or usable spaces located below grade. Drainage tiles, gravel or crushed stone drains, perforated pipe or other approved systems or material shall be installed at or below the area to be protected and shall discharge by gravity or mechanical means into an approved drainage system. Gravel or crushed stone drains shall extend at least one foot (1’) beyond the outside edge of the footing and six inches (6”) above the top of the footing and be covered with an approved filter membrane material. The top of open joints of drain tiles shall be protected with strips of building paper. Perforated drains shall be surrounded with an approved filter membrane or the filter membrane shall cover the washed gravel or crushed rock covering the drain. Drainage tiles or perforated pipe shall be placed on a minimum of two inches (2”) of washed gravel or crushed rock at least one sieve size larger than the tile joint opening or perforation and covered with not less than six inches (6”) of the same material.

Exceptions:

  1. 1.
    A drainage system is not required when the foundation is installed on well-drained ground or sand-gravel mixture soils according to the Unified Soil Classification System, Group I Soils, as detailed in Table R405.1.
  2. 2.
    A filter membrane is not required where perforated drains are covered with at least eighteen inches (18”) of washed gravel or crushed rock.
  3. 3.
    For gravel or crushed stone drains a filter membrane is not required when the gravel or crushed stone extends at least eighteen inches (18”) above the top of the footing.

R405.1.1 Precast concrete foundation. Precast concrete foundation walls that retain earth and enclose habitable or useable space located below-grade that rest on crushed stone footings shall have a perforated drainage pipe installed below the base of the wall on either the interior or exterior side of the wall, at least one foot (1’) beyond the edge of the wall. If the exterior drainage pipe is used, an approved filter membrane material shall cover the pipe. The drainage system shall discharge into an approved sewer system or to daylight.

(History: Ord. BC-3286 §64, 2020; Ord. BC-2936 §45, 2012)

Effective on: 1/1/1901