SELECTED PORTIONS OF THE
LOS ANGELES BUILDING AND GRADING CODES

IMPORTANT ASPECTS OF THE 1996 CITY OF LOS ANGELES BUILDING CODES RELATING TO HILLSIDE CONSTRUCTION

Section 7007.2 - No person shall conduct any grading excavation or filling, including the export or import of earth material, between the hours of 6pm and 7am, except in emergencies.

Residence Additions :

Section 7005.9 - Whenever the principal building on a site is added to, altered or repaired in excess of 50 percent of its replacement value, the entire site shall be made to conform with the provisions of this chapter (70) and chapter 18.
 

Hillside Planting and Erosion Control :

a. Removal of Ground cover : (Section 7005.3) The existing vegetative ground    cover of any watershed in any hillside area shall not be destroyed.....

b. Restriction of Work during Rainy Season : The period between November 1 and April 15  is hereby determined to be the period in which heavy rainfall normally occurs in the City of Los Angeles and is declared to be the “rainy season”. During this period, no grading work in excess of 200 cubic yards shall be commenced on any single grading site under permit until an erosion control system has been approved and it has been demonstrated to the department’s satisfaction that such grading work will not endanger life, limb, health, property or public welfare. All hillside property owners or their agents shall submit erosion control plans to their district grading inspectors prior to October 1 for unfinished grading projects and sites with substandard conditions, unless specifically exempted by the grading inspectors.

c. Preparing slope for planting (Section 7011.4) - Fill slopes may be prepared for planting by casting topsoil over the face of the slope, not to exceed 3 inches. As an alternative, the slope face may be scarified to a depth not to exceed 3 inches.

d. Planter boxes (Section 2317.8) - Where planter boxes are installed adjacent to wood frame walls, a 2-inch wide air space shall be provided between the planter and the wall. Flashings shall be installed when the air space is less than 6 inches in width. Where flashing is used, provisions shall be made to permit circulation of air in the air space. The wood-frame shall be provided with an exterior wall covering conforming to section 2320.

Drainage :

a. Gutters (Section 7013.9) - Eave or ground gutters shall be provided to receive all roof water and deliver it through a nonerosive device via gravity to a street or watercourse if the slope underlying the natural ground exceeds 3 percent or if more than 3 feet of compacted fill or more than 1 foot of uncompacted fill is placed on the ground.

b. Site drainage (Section 7013.10) - All pads with cut or fill shall slope a minimum of 2 percent to an approved drainage device or to a public street. Where used, the drainage device shall be an adequately designed system of catch basins and drain lines which conducts the water to a street. Exception : When the slope of the underlying natural ground does not exceed 3 percent and the compacted fill is less than 3 feet in depth, the slope of the pad may be reduced to 1 percent.

c. Drainage around Buildings (Section 7013.11) - On all building sites, acceptable drainage devices shall be installed to conduct storm water around buildings, whenever the distance from the building to the top of any slope is less than 5 feet.

d. Berms (Section 7013.3) - Berms conforming to the provisions of Figure 70-3 shall be constructed at the top of all slopes.

Liquefaction :

a. (Section 7006.2) - Geotechnical investigation may be required if shallow ground water (50 feet of less) is encountered or if unconsolidated sandy alluvium is present.

Grading :

a. Permits

A licensed contractor must perform the grading when a project involves more than 100 cubic yards of excavation and involving an excavation in excess of 5 feet in vertical depth at its deepest point measured from the original ground surface. (Section 106.1.2) A permit is not required if it conforms to the following:

    1. An excavation which is less than 2 feet in depth, or which does not create a cut slope greater than 5 feet in height and steeper than 2:1. This exemption does not apply when cuts exceed 50 cubic yards or which changes the existing drainage pattern.

    2. A fill is less than 1 foot in depth and placed on natural terrain with a slope flatter than 2:1. This exemption does not apply when the fill exceeds 50 cubic yards or when the fill changes the existing drainage pattern.

    3. Excavations located within hillside areas, for caissons or piles under buildings or structures authorized by valid building permits.

    4. Excavations, not located in hillside areas, for basements, footings, caissons, piles, swimming pools or underground structures which are authorized by valid building permits.

    5. Excavations for wells or tunnels or utilities, which do not provide vertical or lateral support for buildings or adversely impact the safety or stability of private or public properties.

    6. Grading permits may be waived by the department for excavations under buildings or structures in hillside areas if the applicant can demonstrate that the site is relatively level, or the excavation is entirely for footings and/or grade beams not exceeding 5 feet deep.

b. Cut Slope Height - No cut slope shall exceed a vertical height of 100 feet unless horizontal benches with a minimum width of 30 feet are installed at each 100 feet. (Section 7010)

c. Fill Slope Height - No fill slope shall exceed a vertical height of 100 feet unless horizontal benches with a minimum width of 30 feet are installed at each 100 feet. (Section 7010)

d. Fill Slope Gradients (Section 7011.2) - No fill shall be made which creates an exposed surface steeper than 2:1 (50%). The fill slope abutting and above private property shall be so placed that no portion of the fill lies above a plane through a public property line extending upward at a slope of 2:1. The department or the board, in case an appeal is made to it under Section 105, may permit a fill to be made which creates an exposed surface steeper than 2:1 provided the following:

        1. The use of the steeper slope is determined to be necessary due to special design limitations on the site,

        2. The gradient does not exceed 1-1/2:1 (66.7%),

        3. The applicant shows through investigation, subsurface exploration, analysis and report by a soils engineering and engineering geologist, to the department’s satisfaction, that the fill to be used and the underlying bedrock or soil supporting the fill have strength characteristics sufficient to produce a stable slope which a minimum factor of safety not less than 1.5 for static loads.

f. Protection of Adjoining Property (Section 3301.2.2.1) - Excavations shall not remove the lateral support from a public way, from an adjacent property or from an existing structure. For the purpose of this section, the lateral support shall be considered to have been removed when any of the following conditions exist :

        1. The excavation exposes any adverse geological formations which would affect the lateral support of a public way, or an adjacent property or an adjacent structure

          2. The excavation extends below a plane extending downward at an angle of 45 degrees from the edge of the public way or an adjacent property. EXEMPTION : Normal footing excavations not exceeding 2 feet in depth will not be construed as removing lateral support.

          3. The excavation extends below a plane extending downward at an angle of 45 degrees from the bottom of a footing of an existing structure.

Import/Export :

Setbacks :

a. Top of Cut Slope (Section 7010.3) - The top of cut slopes shall not be made nearer to a site boundary line than 1/5 of the vertical height of cut with a minimum of 2 feet and a maximum horizontal distance of 10 feet. The setback may need to be increased for any required interceptor drains. Setback dimensions shall be horizontal distances measured perpendicular to the site boundary.

b. Toe of slope from property line (Section 7011.5) - The toe of fill slopes shall be made not nearer to a site boundary line adjoining other private properties than ½ the height of the fill slope with a minimum of 2 feet and a maximum of 20 feet. In the event retaining walls are constructed to retain fill, the height of the fill shall be measured from the elevation of the fill behind the wall and the setback distance may be measured from the face of the wall to the boundary line.

c. Swimming Pools (Section 1806.4.4) - The setback between pools and slopes is h/4, where h is the height of the slope, maximum of 7 feet. All pool walls closer than 7 feet from the top of any descending slope shall be designed as free-standing.

d. Foundation Setback (Section 1806.4.2) - h/3, where h is the height of the slope, maximum of 15 feet for slopes steeper than 3:1 (33.3%).

e. Alternate setback and clearance (Section 1806.4.6) - The building official may approve alternate setbacks and clearances. The building official may require an investigation and recommendation of a qualified engineer to demonstrate that the intent of this section has been satisfied. Such an investigation shall include consideration of material, height of slope, slope gradient, load intensity and erosion characteristics of slope material.

Friction Piles and Caissons :

a. Two direction ties (Section 1807.2) - Individual pile caps and caissons of every structure subjected to seismic forces shall be interconnected by ties. Such ties shall be capable of resisting, intension or compression, a minimum horizontal force equal to 10% of the larger column vertical load.

b. Downward pressure (Section 1807.7) - Where piles are driven through subsiding fills or other subsiding strata and derive support from underlying firmer materials, consideration shall be given to the downward frictional forces which may be imposed on the piles by the subsiding upper strata.

c. Grade Beams (Section 1634.10.1) - grade beams shall extend at least 12 inches below the lowest adjacent grade and provide a minimum 24-inch distance horizontally from the bottom outside face of the grade beam to the face of the descending slope. Where a footing or grade beam extends across a descending slope, the stem wall, grade beam, or footing shall extend up to a minimum 18 inches above the highest adjacent grade.

Retaining Walls :

a. Arbitrary Design Method (Section 1819.2) - Walls which retain drained earth and are free-standing (cantilevered design less than 15 feet high) or basement walls which have spans of 15 feet or less between supports, may be designed for an assumed equivalent fluid pressure per Table 18-I-E.

b. Gravel backfill (Section 7011.3) - A compaction report is not required for gravel backfill behind retaining walls provided the wall does not exceed 10 vertical feet, the maximum distance between the wall and the backcut does not exceed 24 inches, the gravel backfill is mechanically compacted and covered with concrete pavement or be capped with a 24-inch thick soil blanket mechanically compacted to the department’s satisfaction and provided that the gravel backfill does not provide vertical or lateral support for an structures or adverse bedding planes.

c. Code does not apply (Section 101.5) - Retaining walls which are not over 4 feet in height, measured from the bottom of the footing to the top of the wall, unless supporting a surcharge or sloping earth, or impounding flammable liquids. This exemption shall not apply to retaining walls of any height built on slopes steeper than 5:1 (20 percent).

d. Wood Retaining Walls (Section 1819.6) - No retaining wall shall be constructed of wood or stone.

e. Temporary Shoring (Section 3301.2.2.2) - temporary shoring shall be designed for an equivalent fluid pressure of not less than 30 pounds per cubic foot plus any surcharge loads OR as recommended by the soils engineer

Underfloor Ventilation (Section 2317.7)

a. Underfloor areas shall be ventilated by an approved mechanical means or by openings into the underfloor area walls. Such openings shall have a net area of not less than one square foot for each 150 square feet of underfloor area. Openings shall be located as close to corners as practical and shall provide cross ventilation. Where moisture due to climate and groundwater conditions is not considered excessive, the building official may allow operable louvers and may allow the required net area of vent openings to be reduced to 10% of the required area, provided the underfloor ground surface is covered with an approved vapor retarder.

Expansive Soils :

a. Footings located in expansive soil shall be no less than 24 inches deep for exterior an 18 inches deep for interior footings. Exterior walls and interior bearing walls shall be supported on continuous footings. Footings shall be reinforced with at least two continuous ½ inch diameter deformed reinforcing bars. One bar shall be placed within 4 inches of the bottom of the footing and one within 4 inches of the top of the footings. Section 1804.4

b. Concrete floor slabs on expansive soils shall be placed on a 4-inch fill of coarse aggregate or on a moisture barrier membrane. The slabs shall be at least 3-1/2 inches thick and shall be reinforced with welded wire mesh or deformed reinforcing bars. Welded wire mesh shall have a cross sectional area of not less than 0.05 inch per foot each way. Reinforcing bars shall have a diameter of not less than 3/8 inch and shall be spaced at intervals not exceeding 24 inches each way. The soil below an interior concrete slab shall be saturated with moisture to a depth of 18 inches prior to placing the concrete. Section 1804.4

            c. Expansive Index (Table 18-I-B)