City of Los Angeles · Mulholland Specific Plan
Site Permeability 50 Percent Maximum
Code Citation
Mulholland Design Guideline 5
Mulholland Design Guideline 5
Definition
Mulholland Design and Preservation Guideline 5 caps non-permeable surfaces at 50 percent of lot area. Driveways, patios, pool decks, building footprints, and other impermeable elements are aggregated against this cap. The guideline supports the Plan’s purposes regarding ecological balance, hillside stability, and stormwater management.
What Counts as Non-Permeable
- Building footprint (all enclosed and roofed structures).
- Driveways and turn-around areas (concrete, asphalt, pavers without permeable bedding).
- Patios and pool decks.
- Tennis and sport courts.
- Solid retaining walls (footprint, not necessarily face).
- Other impermeable hardscape.
What Counts as Permeable
- Permeable pavers with appropriate bedding (verified by section detail).
- Decomposed granite walks.
- Lawn, planting beds, native vegetation.
- Pool water surface (verify treatment per current City interpretation).
- Decks above grade with gaps allowing water passage to subgrade.
Guideline ExcerptTotal non-permeable surfaces should not exceed 50 percent of lot area. (Guideline 5, Mulholland Design and Preservation Guidelines, amended September 24, 2009.)
What Plan Check Looks For
- Total non-permeable area calculation on the Plot/Site Plan, with each surface identified and area shown.
- Aggregation against 50 percent of total lot area.
- Permeable claim supported by section detail (for example, permeable paver assembly with subsurface drainage).
- Coordination with the LID (Low Impact Development) plan where applicable.
- Consistency with Guideline 11 (landform grading) and §10 (landscaping).
Upstream Decisions
- Run the permeability calculation at the schematic stage. The 50 percent cap shapes driveway design, patio footprint, and the relationship between building and outdoor living spaces.
- For lots near the cap, consider permeable pavers, decomposed granite, or above-grade decking as substitutes for solid hardscape.
- Coordinate with the LID consultant. Site permeability and stormwater BMP design are mutually reinforcing.
- For pool projects, the pool itself often counts toward non-permeable; the deck is a separate area to evaluate.
Worked ExampleA 12,000-square-foot lot proposes a 3,800-square-foot building footprint, a 1,200-square-foot driveway and turn-around, an 800-square-foot patio, and a 600-square-foot pool with a 700-square-foot pool deck. Total non-permeable area: 3,800 + 1,200 + 800 + 600 + 700 = 7,100 square feet. The 50 percent cap is 6,000 square feet. The design exceeds the cap by 1,100 square feet.
The applicant revises: the driveway is rebuilt with permeable pavers (verified by section detail and bedding); the pool deck is reduced to 500 square feet; and the patio is rebuilt with decomposed granite. Revised non-permeable area: 3,800 (building) + 0 (permeable driveway) + 0 (permeable patio) + 600 (pool) + 500 (deck) = 4,900 square feet — comfortably within the cap.
Source: Mulholland Design and Preservation Guidelines, Guideline 5 (site permeability). Adopted September 24, 2009 as part of Ordinance No. 167,943. Coordinates with §10 (Landscaping) and Guideline 11 (Landform Grading).
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