MEP Plans in Mariposa County, CA

Mariposa County project facts we design around

County seat	Mariposa
Population	17,048 (Census 2024 estimate)
Incorporated cities	None: the whole county is unincorporated
Permits in unincorporated areas	Mariposa County Building Department
Title 24 climate zones	CZ 12 (about 89% of residents), CZ 16 (about 10% of residents), CZ 13 (about 1% of residents). Confirmed by ZIP for every project
ADU approval timeline	Approve or deny within 60 days of a complete application (state law)

HVAC design across Mariposa County

Climate Zone 12 and 13: Central Valley-style climate — hot summers, cool winters (about 90% of residents)

This is a two-sided load: long stretches above 100°F in summer and cold, foggy winter mornings. The heat pump is usually sized for cooling, then checked to make sure it still carries the heating load at the local winter design temperature. High summer peaks also mean the AC is often the single biggest electrical load, which is what pushes many ADUs into a panel or service upgrade.

• Heat pump sized for cooling and verified for winter heating
• Panel / subpanel sizing that accounts for a large cooling load
• Title 24 envelope and HVAC assumptions that hold up in a demanding zone

Climate Zone 16: mountain climate with cold, snowy winters (about 10% of residents)

Heating, not cooling, sets the design here. Climate Zone 16 is the most heating-dominated zone in California, with freezing nights for much of the year and snow at higher elevations. Heat pumps need to be cold-climate models that keep their capacity at low outdoor temperatures, with the outdoor unit mounted above expected snow depth and clear of snow sliding off the roof. Where there is no natural gas service, propane often supplies backup heat, cooking or water heating, and its piping belongs on the plan.

• Cold-climate heat pump sized for the local winter design temperature
• Outdoor unit placed above snow depth and away from roof snow shedding
• Freeze protection for water lines and a protected water heater location

Permits in Mariposa County

Because Mariposa County has no incorporated cities, the county reviews every ADU and residential permit. County plan check reviews MEP drawings against the same California Mechanical, Electrical and Plumbing Codes and the Title 24 Energy Code as any city, but the submittal checklist, forms and fees are the county's own, so we prepare the set to match. In rural areas, parcels outside a sewer district often rely on a private septic system; adding an ADU can require the county's environmental health division to confirm the system has capacity, and the plumbing plan then shows the connection to the septic tank instead of a sewer lateral.

What's in a Mariposa County MEP set

• Mechanical: HVAC layout, Manual J load calculation, equipment schedule, exhaust and whole-unit ventilation
• Electrical: power and lighting plan, panel schedule, NEC 220 load calculation, single-line diagram
• Plumbing: supply and DWV layout, fixture units, water heater, gas (if any), sewer or septic connection
• Title 24 (add-on): energy compliance for your address's climate zone, coordinated with the MEP design so the two documents agree

Pricing is flat statewide: ADU plans from $995, full ADU MEP package from $2,295, Title 24 add-on $240. Standard turnaround is 5 business days with two revisions and corrections included.

Mariposa County cities and communities

Place	Climate zone	Electric utility
Catheys Valley (unincorporated)	CZ 12	Pacific Gas and Electric (PG&E)
Mariposa (unincorporated)	CZ 12	Pacific Gas and Electric (PG&E)

Shown for most addresses in each city. We also serve every unincorporated community in the county.

Mariposa County ADU MEP questions

Who issues building permits for an ADU in unincorporated Mariposa County?

Mariposa County has no incorporated cities, so ADU and residential building permits throughout the county go through Mariposa County Building Department. We prepare the MEP set to that office's plan-check standards.

What Title 24 climate zones are in Mariposa County?

Mariposa County spans 3 Title 24 climate zones: CZ 12 (about 89% of residents), CZ 16 (about 10% of residents), CZ 13 (about 1% of residents). Zones follow ZIP-code boundaries, so we confirm the zone from your project address before sizing the HVAC or running the Title 24 report.

Who provides electric service in Mariposa County?

It depends on the address. In the Mariposa County places listed on this page, most addresses are served by Pacific Gas and Electric (PG&E). We confirm the serving utility for every project, because service upgrades and new meters are requested from the utility, separately from the building permit.

How much do ADU MEP plans cost in Mariposa County?

Our pricing is flat across California: single-discipline ADU plans start at $995, a full MEP package for an ADU up to 600 SF is $2,295, and a Title 24 report can be added for $240. Residential (single-family) full MEP packages start at $3,495. Standard turnaround is 5 business days, and corrections are included.

How long does ADU approval take in Mariposa County?

California law requires local agencies, counties included, to approve or deny a complete ADU permit application within 60 days. Incomplete or inconsistent drawings are the most common reason the clock restarts, which is why MEP plans that match the architectural set, and a Title 24 report that matches the MEP design, matter.