16.02.220 Amend Section 1907.1 General.
Section 1907.1 General is deleted and based upon Express Findings 1 and 3 in Section 16.02.040 is amended to read as follows:
1907.1 General. The thickness of concrete floor slabs supported directly on the ground shall not be less than 3 1/2 inches (89 mm). A 6-mil (0.006 inch; 0.15 mm) polyethylene retarder with joints lapped not less than 6 inches (152 mm) shall be placed between the base course or subgrade and the concrete floor slab, or other approved equivalent methods or materials shall be used to retard vapor transmission through the floor slab. As a minimum and in all cases where a slab is to be placed inside of a building, the slab shall be reinforced with not less than six inches by six inches ten-gauge welded wire mesh or an approved alternate installed at mid height of the slab.
Exception: A vapor retarder is not required:
(1) For detached structures accessory to occupancies in Group R-3, such as garages, utility buildings or other unheated facilities.
(2) For unheated storage rooms having an area of less than 70 square feet (6.5 m2) and carports attached to occupancies in Group R-3.
(3) For buildings of other occupancies where migration of moisture through the slab from below will not be detrimental to the intended occupancy of the building.
(4) For driveways, walks, patios and other flatwork which will not be enclosed at a later date.
(5) Where approved based on local site conditions.
In all slabs under habitable spaces, a 4-inch (10 mm) crushed rock capillary water barrier shall be provided under the minimum 6 mil vapor retarder.