Planned drainage paths which prevents the water and moisture to enter into the building and protects the exterior.
CALGreen Code Section 5.106.10: Grading and paving.
Construction plans shall indicate how site grading or a drainage system will manage all surface water flows to keep water from entering buildings. Examples of methods to manage surface water include, but are not limited to, the following:
2. Water collection and disposal systems.
3. French drains.
4. Water retention gardens.
5. Other water measures which keep surface water away from buildings and aid in groundwater recharge.
Exception: Additions and alterations not altering the drainage path.
The intent of this code requirement is to ensure that newly constructed project sites, additions and alterations that redefine drainage paths are planned and developed to keep surface water from entering the building to extend the longevity of the exterior building walls and to keep moisture from entering the exterior wall and perimeter floor systems. See Chapter 3 for exceptions for additions and alterations.
Sections in the California Building Code (for example, Section 1808.7.4 Foundation elevation) that address sloping grades away from buildings but do not address how all surface water flows will be managed on site.
Show on the construction documents (site or grading plan) how grading and/or a drainage system will manage all surface water flows to keep water from entering the building. This is particularly critical on sloped sites.
Show on the grading plan, in addition to redirecting the water away from the exterior walls, how surface water will be managed on site. Methods include, but are not limited to, those listed in the regulation.
Plan intake: The reviewer and/or plan checker should review the grading plan and confirm that there are slopes away from the building and adequate measures to manage surface water flows. In addition, the reviewer should ensure that the plans indicate protection from water intrusion for buildings located on sloped sites or having flood plain requirements.
On-site enforcement: The inspector should verify that all grading and/or drainage systems have been installed as designed on the approved construction documents and that floor elevations are correctly set with respect to adjacent grades.
(Excerpted from ‘Guide to the 2019 California Green Building Standards Code Nonresidential’ – Chapter 5)