What Title 24 forms are required for a California TI mechanical permit?

A California commercial TI mechanical permit submission typically requires the NRCC-MCH-01 (Certificate of Compliance - Mechanical), plus any applicable sub-forms: NRCC-MCH-02 for fan systems, NRCC-MCH-03 for economizers, and NRCC-MCH-05 for HVAC controls. These must be generated in CEC-approved compliance software (EnergyPro or CBECC-Com) and signed by the responsible person. Acceptance test forms (NRCA-MCH) must also be listed in the permit set.

Do I need stamped plans from a mechanical engineer for a California TI HVAC permit?

Whether stamped plans are required depends on the AHJ and project size. Most California AHJs require engineer-stamped mechanical drawings for any TI with new or relocated HVAC systems over 5 tons, any project with duct work in unconditioned space, and any project in a high-occupancy or life-safety occupancy. Some AHJs allow C-20 contractor self-certification for minor HVAC alterations under 5 tons. When in doubt, use stamped plans - they almost always reduce correction cycles.

What is the most common TI HVAC plan check rejection in California?

The most common first-round rejection is an incomplete NRCC-MCH package - either the equipment schedule data doesn't match the compliance software inputs, the compliance software run is from a prior Title 24 code cycle, or the economizer documentation is missing entirely. The second most common is missing or incomplete ventilation calculations showing occupant-based outside-air rates per ASHRAE 62.1 and CMC Table 4-4.

What is the permit sequence for TI HVAC in California?

The typical California TI permit sequence is: (1) Architectural and structural drawings submitted by GC; (2) Mechanical sub submits concurrent mechanical plan check with Title 24 package, equipment schedule, and ventilation calcs; (3) Plan check correction cycle resolved; (4) Mechanical permit issued; (5) Rough-in inspection (ductwork, equipment before ceiling close); (6) HERS rater duct leakage test; (7) Startup and acceptance testing; (8) Final mechanical inspection. The HERS test must precede the final inspection.

How does a C-20/C-43 contractor coordinate with the architect on a TI?

The most efficient TI permit process has the C-20/C-43 mechanical contractor involved at or before schematic design - providing equipment selection input, confirming roof penetration and structural-loading requirements, and reviewing the reflected ceiling plan for duct coordination. The mechanical sub generates the NRCC-MCH compliance package; the mechanical engineer of record (if required) stamps it. The architect of record coordinates all permits but the mechanical permit application is typically filed by the C-20 contractor.

Permitting · Tenant Improvements · Published 2026-06-03

California tenant improvement HVAC: how to write a mechanical scope of work that gets permitted first try

A first-round plan-check rejection on a TI mechanical permit costs the project 4–6 weeks. It also damages the relationship between the GC and the mechanical sub. This guide walks through exactly what a complete California TI mechanical scope of work must contain - from the equipment schedule through the NRCC-MCH compliance package - and the five most common rejection triggers we see across California AHJs.

Tenant improvement HVAC rough-in with ductwork and equipment installation in progress — TI mechanical rough-in in progress. A complete first-submission permit package avoids the 4–6 week correction-cycle delay.

What triggers a mechanical permit on a California TI

Any work that adds, relocates, replaces, or modifies HVAC equipment or ductwork in a commercial building requires a mechanical permit in California. The California Mechanical Code (CMC Section 104.1) is explicit: the threshold is low. Even adding a new diffuser to an existing branch duct - if it requires cutting into the duct - typically requires a permit in most jurisdictions.

In practice, the TI mechanical permit scope typically includes: replacement or addition of packaged rooftop units (RTUs) or split systems; relocation or installation of supply and return ductwork; addition of exhaust fans or makeup air units; modification of the HVAC controls or thermostat strategy; and any work that requires a new or modified penetration through a fire-rated assembly.

Note that permit-exempt items in California (CMC Section 104.2) include minor duct modifications that do not penetrate rated assemblies and replacement of a like-for-like piece of equipment in the same location - but even the like-for-like exemption disappears if the replacement unit uses a different refrigerant, has a different BTU capacity, or requires a new electrical circuit. When in doubt, pull the permit. The risk of an unpermmitted TI HVAC installation is a stop-work order, correction costs, and CO delay.

The complete California TI mechanical scope of work: what every permit set needs

A complete California TI mechanical permit submission has five primary components. Missing any one of them typically generates an immediate first-round correction.

1. Equipment schedule

The equipment schedule is the foundation of the permit set and the compliance documentation. It must list, for each piece of HVAC equipment:

Manufacturer name and model number (not just a description - "3-ton RTU" is not sufficient)
Cooling capacity (BTU/hr or tons) and heating capacity (BTU/hr or kW)
EER, IEER, or SEER2 (as applicable to equipment type)
Refrigerant type and system charge weight
Electrical characteristics: voltage, phase, full-load amps
Physical dimensions and operating weight (for structural and rooftop loading)
Supply CFM and external static pressure

The equipment schedule data must match exactly what is entered into the Title 24 compliance software. Mismatches between the schedule and the NRCC-MCH forms are the most common cause of first-round corrections.

2. Ventilation calculations

California Mechanical Code Table 4-4 and ASHRAE 62.1 require minimum outside-air (OA) rates by occupancy type. The mechanical scope of work must show, zone by zone:

Zone occupancy type (office, retail, restaurant dining, conference, etc.)
Design occupant density (people per 1,000 sq ft)
Zone floor area
Minimum OA rate in CFM per person plus CFM per sq ft
Total OA CFM per zone and per AHU

If demand controlled ventilation (DCV) is triggered by occupant density, show CO₂ sensor locations and setpoints on the drawing. Failure to show DCV documentation when it is required is one of the top five TI rejection triggers.

3. Title 24 NRCC-MCH compliance package

The NRCC-MCH package is mandatory for all commercial mechanical work subject to Title 24 Part 6. It must be generated using CEC-approved software (EnergyPro or CBECC-Com), referencing the correct code cycle - as of January 1, 2026, that is the 2025 California Energy Code. A compliance run from the 2022 code cycle submitted on a post-January 2026 permit application will be rejected outright.

Required NRCC-MCH sub-forms for a typical TI:

NRCC-MCH-01: Certificate of Compliance - Mechanical (required for all projects)
NRCC-MCH-02: Fan systems and motor data (required when fan systems are new or modified)
NRCC-MCH-03: Economizer documentation (required for RTUs 3 tons and larger in most climate zones)
NRCC-MCH-05: HVAC controls and DCV (required when DCV or BAS controls are specified)

The compliance documentation must be signed by the responsible person - typically the mechanical engineer of record or, for self-certified projects, the C-20 contractor. For acceptance testing, the NRCA-MCH forms must also be listed in the permit set, though they are completed at startup, not at plan check.

4. Duct layout and system drawings

The duct layout drawings must show supply, return, and OA paths on the plan at sufficient scale to verify routing, duct sizing, and coordination with structure. Key elements:

Duct sizes labeled on plan (not just shown schematically)
Duct material and pressure class (CMC Table 6-1 compliance)
Insulation R-value for ducts in unconditioned space
Access panels at required locations (every 10 feet on concealed systems)
If ducts pass through fire-rated assemblies: rated damper schedule and/or shaft detail
Duct leakage compliance path: notation of Class 1 duct and sealing method, or reference to HERS duct leakage test

5. Acceptance test scope (NRCA-MCH)

Some AHJs - Sacramento, Oakland, and several Bay Area jurisdictions - now require that the acceptance test scope be identified in the permit set, not just at closeout. The NRCA-MCH forms define the functional tests required after installation: economizer control verification, DCV sensor calibration, fan efficacy measurement, and refrigerant charge verification. Listing the acceptance test scope in the permit set demonstrates that the contractor understands what compliance testing is required and reduces last-minute disputes at the final inspection.

Stamped plans vs. self-certification: which AHJs require which

California does not have a single statewide rule on whether TI mechanical plans must be stamped by a licensed mechanical engineer. Each AHJ sets its own threshold, and these thresholds vary considerably:

Sacramento (City and County): Engineer stamp required for systems over 5 tons or any project with ductwork in unconditioned space exceeding 500 linear feet. Below those thresholds, C-20 self-certification is accepted on most TI scope.
Los Angeles (LADBS): Engineer stamp required for all new commercial HVAC over 5 tons. Self-certification allowed only for minor alterations (adding or relocating fewer than 5 diffusers on an existing system).
San Francisco DBI: Engineer stamp required for all commercial mechanical permits, no exceptions for TI scope.
Santa Clara County cities (San Jose, Sunnyvale): Engineer stamp required for systems over 10 tons or any project adding new equipment to an existing system.
Smaller cities (Modesto, Redding, Stockton): Many accept C-20 contractor self-certified plans for TI HVAC under 10 tons with no life-safety occupancy change.

For projects where stamped plans are borderline, our experience is that using an engineer stamp almost always reduces correction cycles and speeds plan check approval - the cost of the engineer's stamp is recovered in schedule time. A companion resource: our guide to responding to a California mechanical plan check correction letter covers how to structure a correction response to get back-check approval faster.

The top 5 TI HVAC plan check rejection triggers

NRCC-MCH package incomplete or wrong code cycle. Missing sub-forms, software run from the wrong Title 24 cycle, or equipment schedule that doesn't match the compliance inputs. Fix: generate the complete NRCC-MCH package in the correct code cycle before submitting, and cross-check equipment schedule against compliance inputs line by line.
Ventilation calculations absent or incomplete. No per-zone OA CFM calculation, or OA rates based on "rule of thumb" rather than the CMC/ASHRAE 62.1 procedure. Fix: include a ventilation calculation table in the permit set showing occupancy type, density, area, and calculated OA CFM.
Economizer documentation missing for RTUs 3 tons and larger. Many contractors forget that Title 24 § 140.4(e) requires an air-side economizer on most commercial RTUs 3 tons and larger, and that the NRCC-MCH-03 form must document compliance. Fix: include NRCC-MCH-03 and verify the equipment model includes an economizer or a field-installed economizer kit is specified.
DCV missing where occupant density triggers it. Conference rooms, training rooms, restaurant dining, and fitness spaces routinely exceed the 25-person-per-1,000-sf trigger. Fix: check DCV trigger for every zone; if triggered, add CO₂ sensors to the equipment schedule and show sensor locations on the plan.
Duct leakage compliance path not stated. Ducts in unconditioned space must show how duct leakage compliance will be achieved - Class 1 duct with sealing noted, or a HERS duct leakage test scope. Fix: add a duct leakage compliance note to the drawing set, and if HERS testing is required, note it in the acceptance test scope.

How the C-20/C-43 contractor coordinates with the architect

The most efficient TI permit sequences happen when the mechanical contractor is engaged at or before schematic design - not at permit submittal. Early mechanical involvement allows: equipment selection input before the architectural set is committed (avoiding conflicts with structural, roofing, and ceiling designs); ventilation strategy input before the reflected ceiling plan is drawn; coordination of roof penetrations and curb blocking; and early Title 24 compliance run to flag any equipment that cannot meet the NRCC-MCH requirements.

At the permit submission stage, the typical document exchange is: architect provides the floor plan and reflected ceiling plan as PDF; mechanical contractor generates the mechanical plan sheet and compliance package; mechanical engineer of record (if required) stamps the drawing; architect coordinates all permits but the mechanical permit is filed separately by the C-20 contractor. The GC Partners section of our website covers how we structure this coordination for commercial GCs running multi-site TI programs. For individual project inquiries, contact our bid desk.

Working with Sierra Mechanical on California TI projects

We prepare mechanical permit sets - equipment schedules, NRCC-MCH packages, ventilation calculations, and duct layout drawings - as part of our standard bid and construction scope on every California TI project. Our in-house NRCC-MCH documentation team uses EnergyPro on the 2025 code cycle. We have filed with every major California AHJ and have a first-round correction rate well below industry average on mechanical-only permits.

For duct leakage testing requirements and what GCs should expect from a California mechanical sub, see our companion articles. To start a TI mechanical scope: send us the architectural floor plan, building address, and occupancy type. Bid desk: (916) 638-8605. Request a bid online.

References: California Mechanical Code (2025); California Energy Code Title 24 Part 6 (2025 edition) §§ 120.1, 140.4; ASHRAE Standard 62.1-2022; CEC compliance forms NRCC-MCH-01 through -05. Information current as of 2026-06-03.

This article is general guidance. Consult your local AHJ and a licensed mechanical engineer for project-specific permit requirements.