MEP Plans in Castaic, CA
Permit-ready mechanical, electrical and plumbing plans for ADUs, garage conversions, additions and single-family homes in Castaic (unincorporated Los Angeles County), prepared for plan check at Los Angeles County Public Works – Building and Safety, with Title 24 available in the same order.
Castaic project facts we design around
| County | Los Angeles County (unincorporated) |
|---|---|
| Title 24 climate zone | Climate Zone 9, confirmed by ZIP for every project |
| Electric utility (most addresses) | Southern California Edison (SCE) |
| Permits issued by | Los Angeles County Public Works – Building and Safety |
| ADU permits issued, 2021–2025 | 11 |
| ADU approval timeline | Approve or deny within 60 days of a complete application (state law) |
ADU building activity in Castaic
Los Angeles County issued 11 ADU building permits from 2021 through 2025 for addresses in Castaic, based on the county's reports to the state. Permits went from 2 in 2021 to 4 in 2025.
| 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|
| 2 | not reported | not reported | 5 | 4 |
Source: California Department of Housing and Community Development, Annual Progress Report data (ADU building permits by year).
Title 24 in Climate Zone 9
- Windows: U-factor 0.30 or lower and solar heat gain coefficient (SHGC) 0.23 or lower, with total window area up to 20% of floor area (west-facing up to 5%).
- Whole-house fan required (at least 1.5 cfm per square foot of floor area); units of 500 sq ft or less are exempt.
- Solar PV sized by the CEC formula kW = (floor area x 0.613) / 1000 + 1.36; no PV is required if that is under 1.8 kWdc, which for a single ADU works out to about 718 sq ft or smaller.
Climate Zone 9 requirements in full →
HVAC design for Castaic
The HVAC is sized from a room-by-room Manual J using the outdoor design conditions for the address, in Climate Zone 9's inland climate with hot summers. Cooling-driven Manual J with real window orientation and glazing.
Electrical service from Southern California Edison (SCE)
If the load calculation shows you need a service upgrade, a second meter or a relocated service, Southern California Edison (SCE) handles that through its Building, Renovation, and Project Planning Portal, separately from the building permit.
ADU electrical service with Southern California Edison (SCE) →
Plumbing and sewer
The plumbing plan shows the route, slope and cleanouts of the connection to the existing sewer lateral or septic system.
Pricing is flat statewide: ADU plans from $995, full ADU MEP package from $2,295, Title 24 add-on $240. See what's in a complete ADU MEP set.
Nearby places compared
| Place | Climate zone | Electric utility | ADU permits 2021–25 |
|---|---|---|---|
| Los Angeles | CZ 9, 8, 6, 16 | Los Angeles Department of Water and Power (LADWP) | 52,059 |
| Long Beach | CZ 6, 8 | Southern California Edison (SCE) | 3,015 |
| Glendale | CZ 9 | Glendale Water and Power | 2,945 |
| Burbank | CZ 9 | Burbank Water and Power | 1,376 |
| Torrance | CZ 6, 8 | Southern California Edison (SCE) | 1,051 |
| Downey | CZ 8 | Southern California Edison (SCE) | 1,020 |
Los Angeles County → · All California cities and communities →
Guides for Castaic projects
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Start My OrderGeneral guidance, not legal advice. Climate zone and utility are shown for most addresses in Castaic; requirements vary by project. Confirm with Los Angeles County Public Works – Building and Safety.