FINDINGS FOR ORDINANCE NO. 2025-19
1 CONTRA COSTA COUNTY
FINDINGS IN SUPPORT OF CHANGES, ADDITIONS, AND DELETIONS
TO STATEWIDE BUILDING STANDARDS CODE
The California Building Standards Commission has adopted and published the 2025 Building Standards Code, which is comprised of the 2025 California Building, Residential, Electrical, Mechanical, Plumbing, Energy, Historical Building, Existing, and Green Building Standards Codes. These codes are enforced in Contra Costa County by the Building Inspection Division of the Department of Conservation and Development.
Although these codes apply statewide, Health and Safety Code sections 17958.5 and 18941.5 authorize a local jurisdiction to modify or change these codes and establish more restrictive building standards if the jurisdiction finds that the modifications and changes are reasonably necessary because of local climatic, geological, or topographical conditions. For amendments to the California Green Building Standards Code, local climatic, geological, and topographical conditions include local environmental conditions.
Ordinance No. 2025-19 adopts the statewide codes and amends them to address local conditions.
Pursuant to Health and Safety Code section 17958.7, the Contra Costa County Board of Supervisors finds that the more restrictive standards contained in Ordinance No. 2025-19 are reasonably necessary because of the local climatic, geological, and topographic conditions that are described below.
I. Local Conditions
A. Geological and Topographic
1. Seismicity
(a) Conditions
Contra Costa County is mapped as Seismic Design Categories D and E, indicating very high risk for earthquakes. Buildings and other structures in these zones can experience major seismic damage. Contra Costa County is near numerous earthquake faults including the San Andreas Fault, and all or portions of the Hayward, Calaveras, Concord, Antioch, Mt. Diablo, and other lesser faults. (b) Impact
A major earthquake could severely restrict the response of Contra Costa County Fire Districts and their capability to control fires. When buildings not equipped with earthquake structural support move off their foundations, gas pipes may rupture. Fires may develop from line ruptures and spread from house to house, causing an extreme demand for fire protection resources. The proximity of large areas within the County to fault traces necessitates adopting stricter structural construction standards.
FINDINGS FOR ORDINANCE NO. 2025-19
2 2. Soils
(a) Conditions
The area is replete with various soils, many of which are expansive. Many areas have landslide prone soils, and some areas are potentially liquefiable during severe seismic shaking.
Throughout Contra Costa County, the topography and development growth has created a network of older, narrow roads. These roads vary from gravel to asphalt surface and vary in percentage of slope, many exceeding 20%. Several of these roads extend up through the winding passageways in the hills providing access to remote housing subdivisions. Most of these roads are private with no established maintenance program.
(b) Impact
During inclement weather, these roads are subject to rock and mudslides, as well as downed trees, obstructing all vehicle traffic. It is anticipated that during an earthquake, several of these roads would be unpassable preventing fire protection resources from reaching fires caused by gas line ruptures or other sources.
3. Topographic
(a) Conditions
i. Vegetation
Highly combustible dry grass, weeds, and brush are common in the hilly and open space areas adjacent to built-up locations 6 to 8 months of each year. Many of these areas frequently experience wildland fires, which threaten nearby buildings, particularly those with wood roofs, or sidings.
This condition can be found throughout Contra Costa County, especially in those developed and developing areas of the County. Earthquake gas fires due to gas line ruptures can ignite grasslands and stress fire district resources.
ii. Surface Features
The arrangement and location of natural and manmade surface features, including hills, creeks, canals, freeways, housing tracts, commercial development, fire stations, streets, and roads, combine to limit feasible response routes for Fire District resources in and to District areas.
iii. Buildings, Landscaping, and Terrain
Many buildings and building complexes have building access and landscaping features and designs which preclude or greatly limit any approach or operational access to them by Fire District vehicles. In addition, the presence of security gates, roads of inadequate width, and grades that are too steep for Fire District vehicles adversely affect fire suppression efforts.
When Fire District vehicles cannot gain access to buildings involved with fire, the potential for complete loss is realized. Access problems often severely delay fire and smoke control efforts. In existing structures where
FINDINGS FOR ORDINANCE NO. 2025-19
3 pitched roofs have been built over an existing roof, smoke detectors should be required to warn residents of smoke and fire before the arrival of fire personnel.
(b) Impact
The above local geological and topographical conditions increase the magnitude, exposure, accessibility problems, and fire hazards presented to the County fire resources. Fire following an earthquake has the potential of causing greater loss of life and damage than the earthquake itself. Most earthquake fires are caused by natural gas line ruptures. Hazardous materials, particularly toxic gases, could pose the greatest threat to the largest number, should a significant seismic event occur.
Other variables may intensify the situation:
• The extent of damage to the water system.
• The extent of isolation due to bridge and/or freeway overpass collapse. • The extent of roadway damage and/or amount of debris blocking the roadways.
•
Climatic condition (hot, dry weather with high winds).
• Time of day will influence the amount of traffic on roadways and could intensify the risk to life during normal business hours. •
The availability of timely mutual aid or military assistance. • The large portion of dwellings with wood shake or shingle coverings (both on the roof diaphragm and sides of the dwellings) could result in conflagrations.
•
The large number of dwellings that slip off their foundations and rupture gas lines and electrical systems resulting in further conflagrations.
More restrictive electric vehicle charging standards, construction and demolition waste recovery requirements, and building electrification requirements would not impact the availability of the County’s fire or public safety resources.
B. Climatic
1. Precipitation and Relative Humidity
(a) Conditions
Precipitation ranges from 15 to 24 inches per year with an average of approximately 20 inches per year. 96% of precipitation falls during the months of October through April, and 4% from May through September. May through September is a dry 5-month period each year. Additionally, the area is subject to occasional drought. Relative humidity remains in the middle range most of the time. It ranges from 45 to 65% during spring, summer, and fall, and from 60 to 90% in the winter. It occasionally falls as low as 15%.
(b) Impact
Locally experienced dry periods cause extreme dryness of untreated wood shakes and shingles on buildings and non-irrigated grass, brush and weeds, which are
FINDINGS FOR ORDINANCE NO. 2025-19
4 often near buildings with wood roofs and sidings. Such dryness causes these materials to ignite very readily and burn rapidly and intensely. Gas fires due to gas line ruptures can also spark and engulf a single-family residence during these dry periods.
Because of dryness, a rapidly burning gas fire or exterior building fire can quickly transfer to other buildings by means of radiation or flying brands, sparks or embers. A small fire can rapidly grow to a magnitude beyond the control capabilities of the Fire District resulting in an excessive fire loss.
2. Greenhouse Gas Emissions
(a) Conditions
The California Air Resources Board has collected information on emissions from air pollution sources since 1969. This information is periodically compiled by State and local air pollution control agencies to create regional and statewide greenhouse gas emissions inventories. The California greenhouse gas emissions inventory maintains information on various air pollution sources and identifies “transportation” (all on-road vehicles such as automobiles and trucks, and off- road vehicles such as trains, ships, aircraft, and farm equipment) as a primary pollution source. According to the 2020-2022 statewide inventory (2024 Edition), the transportation sector remains the largest source of greenhouse gas emissions, accounting for 37.7% of the total greenhouse gas emissions. Emissions from waste, comprising 2.2% of the total greenhouse gas emissions, have grown by
14.1% since 2000, and 96% of that amount is landfill emissions. California adopted land use and transportation policies and mandatory recycling laws to help reduce greenhouse gas emissions by promoting the use of renewable energy sources and reducing landfill disposal.
On November 5, 2024, Contra Costa County adopted its 2045 General Plan and 2024 Contra Costa County Climate Action and Adaptation Plan (CAAP). An updated local greenhouse gas emission inventory was included as part of the 2024 CAAP. For the purpose of reducing greenhouse gas emissions, the C2024 CAAP contains 29 climate action strategies, 11 of which directly result in greenhouse gas emission reductions. These strategies include, among other things, actions to support limiting the amount of waste disposal in landfills, actions to increase the installation of electric vehicle charging stations for all vehicle types as well as actions to increase the use of zero-emission vehicles throughout unincorporated Contra Costa County.
(b) Impact
More restrictive electric vehicle charging standards and construction and demolition waste recovery requirements would be consistent with the intent of State legislation and County requirements to aggressively implement energy and waste policies designed to ensure success in meeting their greenhouse gas emission reduction goals.
FINDINGS FOR ORDINANCE NO. 2025-19
5 3. Temperature
(a) Conditions
Temperatures have been recorded as high as 114° F. Average summer highs are in the 75° to 90° range, with average maximums of 105° F in some areas of unincorporated Contra Costa County.
(b) Impact
High temperatures cause rapid fatigue and heat exhaustion of firefighters, thereby reducing their effectiveness and ability to control large building, wildland fires, and fires caused by gas line ruptures.
Another impact from high temperatures is that combustible building material and non- irrigated weeds, grass and brush are preheated, thus causing these materials to ignite more readily and burn more rapidly and intensely. Additionally, the resultant higher temperature of the atmosphere surrounding the materials reduces the effectiveness of the water being applied to the burning materials. This requires that more water be applied, which in turn requires more fire resources to control a fire on a hot day. High temperatures directly contribute to the rapid growth of fires to an intensity and magnitude beyond the control capabilities of the Fire Districts in Contra Costa County. The change of temperatures throughout the County between very low and extreme highs contributes to a voltage drop in conductors used for power pole lines. This necessitates that voltage drops be considered.
More restrictive electric vehicle charging standards, construction and demolition waste recovery requirements, and building electrification requirements would not have a negative impact on the temperature conditions within the County.
4. Winds
(a) Conditions
Prevailing winds in many parts of Contra Costa County are from the north or northwest in the afternoons. However, winds are experienced from virtually every direction at one time or another. Velocities can reach 14 mph to 23 mph ranges, gusting to 25 to 35 mph. 40 mph winds are experienced occasionally and winds up to 55 mph have been registered locally. During the winter half of the year, strong, dry, gusty winds from the north move through the area for several days creating extremely dry condition.
(b)
Impact
Winds such as those experienced locally can and do exacerbate fires, both interior and exterior, to burn, and spread rapidly. Fires involving non-irrigated weeds, grass, brush, and fires caused by gas line ruptures can grow to a magnitude and be fanned to an intensity beyond the control capabilities of the fire services very quickly even by relatively moderate winds. When such fires are not controlled, they can extend to nearby buildings, particularly those with untreated wood shakes or shingles.
Winds of the type experienced locally also reduce the effectiveness of exterior
FINDINGS FOR ORDINANCE NO. 2025-19
6 water streams used by all Contra Costa County Fire Districts on fires involving large interior areas of buildings, fires which have vented through windows and roofs due to inadequate built-in fire protection and fires involving wood shake and shingle building exteriors. Local winds will continue to be a definite factor toward causing major fire losses to buildings not provided with fire resistive roof and siding materials, buildings with inadequately separated interior areas, or buildings lacking automatic fire protection systems, proper gas shut-off devicesor proper electrical systems. National statistics frequently cite wind conditions, such as those experienced locally, as a major factor where conflagrations have occurred.
More restrictive electric vehicle charging standards, construction and demolition waste recovery requirements, and building electrification requirements, would not have a negative impact on the wind conditions within the County.
II. Necessity of More Restrictive Standards
Because of the conditions described above, the Contra Costa County Board of Supervisors finds that there are building and fire hazards unique to Contra Costa County that require the more restrictive fire protection, structural and design load requirements, and energy and waste management policies set forth in Ordinance No. 2025-19.
A. The ordinance amends the 2025 California Building Code by:
1. Requiring the installation of a smoke detector in each existing flat roof building when a pitched roof is added on top of the existing flat roof, and the solid sheathing of the flat roof is not removed. (§ 74-4.002(b).)
2. Requiring wood shakes or shingles used for exterior wall covering to be fire treated. (§ 74-4.002(c).)
3. Requiring special inspections for concrete compressive strength at certain foundations to be consistent with code requirements for concrete at other locations. (§ 74-4.002(d).)
4. Addressing the poor performance of plain concrete structural elements during seismic events. (§ 74-4.002(e), § 74-4.002(g), and § 74-4.002(h).)
5. Prohibiting placement of reinforcement while the concrete is in a semifluid condition thus increasing quality control during construction. Enhanced quality control is necessary because of seismic considerations. (§ 74-4.002(f).)
6. Requiring minimum strength and construction standards for slabs-on-ground. (§ 74-4.002(i).)
B. The ordinance amends the 2025 California Residential Code by:
1. Requiring the installation of a smoke detector in each existing flat roof building when a pitched roof is added on top of the existing flat roof, and the solid sheathing of the flat roof is not removed. (§ 74-4.004(b).)
2. Prohibiting the use of gypsum wallboard as braced wall panels in single- and two- family dwellings and accessory structures, and by limiting the use of Portland
FINDINGS FOR ORDINANCE NO. 2025-19
7 Cement Plaster braced walls to one story single- and two-family dwellings, as these materials have performed poorly during recent California seismic events. (§74- 4.004(c) and §74-4.004(d).)
C. The ordinance amends the 2025 California Green Building Standards Code by:
1. Imposing more restrictive electric vehicle charging standards, as follows:
(a) For new multi-family buildings, requiring ten percent of the total number of parking spaces be equipped with fully-operational Level 2 electric vehicle supply equipment for all multi-family buildings. (§ 74-4.006(c).) (b)
For new non-residential buildings, other than office and retail buildings, increasing the number of designated electric vehicle parking spaces that must have fully functional charging equipment. (§ 74-4.006(h).)
2. Imposing more restrictive construction waste reduction, disposal, and recycling standards consistent with those presently enforced in the County as follows:
(a) Imposing the mandatory restrictions from Chapter 4 of the 2025 CGBSC on certain projects for existing residential buildings, including:
i. Projects that increase the total combined conditioned and unconditioned building area by 5,000 square feet or more. (§ 74-4.006(a).) ii.
Projects that impact 5,000 square feet or more of the total combined conditioned and unconditioned building area. (§ 74-4.006(a).) iii.
Demolition projects when a demolition permit is required, except demolition projects that are necessary to abate a public nuisance. (§ 74-
4.006(a) and § 74-4.006(b).)
(b)
Eliminating the exception from construction waste management requirements for projects solely based on their isolated location from diversion facilities. (§ 74- 4.006(d).)
(c)
Requiring measuring of all generated debris to ensure that at least 65% is diverted from landfills. (§ 74-4.006(g) and § 74-4.006(l).) (d) Requiring more comprehensive documentation for construction waste management be provided to the enforcing agency and making submittal of the same a prerequisite for scheduling final inspections. (§ 74-4.006(e) and § 74-
4.006(j).)
D. The amendments to the 2025 California Existing Building Code are not substantive in nature and are limited to administrative provisions for the use and enforcement of this Code, and to be consistent with the administrative provisions of the statewide codes as amended.
III. Assembly Bill 130 Findings
In addition to the requirement that modifications and changes be reasonably necessary because of local climatic, geological, or topographical conditions, Assembly Bill 130 imposed additional limitations to modifications and changes that impact residential units.
FINDINGS FOR ORDINANCE NO. 2025-19
8 After October 1, 2025, a local jurisdiction may not make any modification or change to these codes that is applicable to residential units, except under specifically enumerated conditions. (Health & Saf. Code, § 17958.5(c).) The enumerated conditions that permit a local jurisdiction to make a modification or change affecting residential units include but are not limited to: (i) the change or modification is substantially equivalent to a change or modification that was in effect as of September 30, 2025 (Health & Saf. Code, § 17958.5(c)(1)), and (ii) the change or modification relates to home hardening (Health & Saf.
Code, § 17958.5(c)(3)).
With one exception, each of the modifications applicable to residential units included in Ordinance No. 2025-19 were also included in Ordinance No. 2022-35, Contra Costa County’s adoption of the 2022 California Building Code with local amendments. The Contra Costa County Board of Supervisors adopted Ordinance No. 2022-35 on November 8, 2022, and the County’s adopted 2022 California Building Code with local amendments was effective on January 1, 2023. According, the modifications applicable to residential units included in Ordinance No. 2025-19, with one exception, are permitted under AB130 because they are substantially similar to modifications that were in effect in Contra Costa County as of September 30, 2025.
Ordinance No. 2025-19 modifies Section 1405.2 of the California Building Code (§ 74-
4.002(c)), to require that
wood shakes or shingles used for exterior wall covering to be fire treated. Ordinance No. 2022-35 also included this modification, but included an exception for when the exterior wall was at least 10 feet from the property line or faced a street. Thus, the modification in Ordinance No. 2025-19 is more restrictive than the modification previously in effect in Contra Costa County. Nevertheless, Ordinance No. 2025-19’s modification to Section 1405.2 is permitted under AB130 because it relates to home hardening as it further protects the subject residential unit from fire and inhibits the spread of fire to surrounding residential units.