Multifamily Residential: 167 Issues Including Critical Mechanical, Fire Protection & Coordination Violations
AI plan review of a multifamily residential project uncovered 167 issues—including 28 critical violations affecting mechanical systems, fire protection, electrical coordination, and document consistency before permit submission.
The Project
A multifamily residential project involving extensive mechanical, electrical, and fire protection systems across multiple floors. The project required strict code compliance with 2018 IMC, 2018 IBC, and 2018 IFC standards, with particular focus on mechanical ventilation, fire protection, and coordination between disciplines.
Code References:
Critical Findings (26)
Missing Fire Dampers at Shaft Penetrations
The mechanical floor plan shows ductwork connecting to a vertical shaft enclosure (indicated by the rectangular symbol with 'X' infill adjacent to the Elevator). There are no fire damper symbols indicated at the point where these ducts penetrate the shaft walls. The International Mechanical Code requires duct penetrations into shafts to be protected with dampers to maintain the fire-resistance rating of the assembly.
Unprotected Multistory Refrigerant Risers
The drawing indicates multiple refrigerant risers (e.g., 'MR 01', 'AAHU-4') with lengths up to 176 feet, confirming they penetrate multiple floors in this residential building. The roof plan depicts these risers as individual penetrations/sleeves ('MR' tags) without enclosing fire-resistance-rated shaft construction. Section 1107.2.2 generally prohibits refrigerant piping from penetrating floors unless enclosed in a shaft (Exception 5.1) or located on the exterior (Exception 5.2).
Potential Mechanical System in Elevator Shaft (IMC 303.8)
Note 3 specifies a 'DEDICATED ... CONNECTION TO MACHINE ROOM INDOOR UNIT' (AC unit). Note 17 identifies the elevator as a 'MACHINE ROOMLESS SYSTEM'. In many Machine Room-Less (MRL) applications, the 'machine room' function is located within the hoistway (shaft). IMC Section 303.8 prohibits mechanical systems (such as HVAC units) in an elevator shaft. If the 'Machine Room Indoor Unit' is installed in the shaft due to the lack of a separate machine room, this violates IMC 303.8.
Missing Mechanical Ventilation and Heating for Occupied Spaces
The drawing M111 is titled 'LEVEL 01 FLOOR PLAN - MECHANICAL' and depicts mechanical ductwork for the parking garage. However, the plan shows multiple occupied spaces—including 'RESIDENT SERVICES OFFICES 01-113', 'LEASING OFFICE 01-116', 'DEMO KITCHEN 01-107', 'COMMUNITY LOUNGE 01-106', and 'FITNESS 01-108'—without any depicted mechanical supply, return, or exhaust systems, ductwork, or terminal units.
Trash Exhaust Discharge Too Close to Outdoor Air Intakes
Plan 14 (ROOF LEVEL GENERATOR) depicts the 'TRASH EXHAUST' outlets (indicated by circular fan symbols) located immediately adjacent to the 'OA SHAFTS' (Outdoor Air Intakes). Based on the drawing scale of 1/4" = 1'-0", the horizontal separation between these exhaust outlets and the air intakes is significantly less than the code-mandated 10 feet (which would be 2.5 inches on the drawing). This configuration poses a high risk of re-entraining noxious odors and contaminants from the trash system into the building's fresh air supply.
Incorrect Ventilation and Pressurization of Accessory Rooms
The drawing contains a note stating 'GARAGE AREA INCLUDES ROOMS' within the Garage Ventilation Calculation block. This indicates that enclosed spaces within the garage footprint—specifically the Elevator Lobby (B1-101), and potentially the Main Electrical (B1-102), Telecom (B1-104), and Storage (B1-107) rooms—are being treated as part of the parking garage ventilation zone. IMC Section 404.2 explicitly requires that occupied spaces accessory to public garages (such as elevator lobbies) be maintained at a positive pressure relative to the garage. Including these rooms in the garage exhaust calculation implies they are part of the negative/neutral pressure zone of the garage, violating the positive pressure requirement.
Prohibited Return Air Path for Fuel-Burning Furnace
Keynote 7 specifies a 'LOUVERED DOOR... FOR RETURN AIR PATH,' which utilizes the mechanical closet space as a return air plenum/path. Simultaneously, Keynote 8 specifies an 'OUTSIDE AIR INTAKE BOX... TO AIR HANDLING UNIT CLOSET,' which is a design characteristic for providing combustion air to a fuel-burning appliance. If the appliance is a fuel-burning forced-air furnace (as implied by the combustion air intake), IMC Section 918.4 strictly prohibits using the furnace enclosure (the closet) as part of the return air path. Circulating air must be conducted to the blower by continuous air-tight ducts from outside the enclosure to prevent backdrafting of combustion gases.
Missing Fall Protection Guards for Rooftop Mechanical Equipment
The drawing shows an 'OPEN MECHANICAL YARD PH-102' with equipment pads located directly adjacent to the building perimeter (roof edge). IMC 304.11 requires a guard where appliances are located within 10 feet of a roof edge. The roof plan indicates the perimeter line but fails to specify a guardrail or a parapet of complying height (minimum 42 inches). A standard roof parapet is often lower than 42 inches, which would be non-compliant for this equipment location.
Incorrect Occupancy Classification of Toilet Rooms
The ventilation schedule (AAHU-1) misclassifies 'MENS' (01-135), 'WOMENS' (01-136), and 'UNISEX' (01-121) rooms as 'Corridor' in the Description column. Consequently, these spaces are assigned the outdoor air rate for Corridors (Area Rate only, Class 1 air) instead of being recognized as Toilet Rooms (Class 2 air). This classification implies the air from these spaces is suitable for recirculation, which violates IMC Section 403.2.1 Item 3, as toilet rooms require mechanical exhaust and their air must not be recirculated to other spaces.
Louvered Door Minimum Free Area Specification Conflict: 16 sqft vs 1.5 sqft
The mechanical keynotes on sheet M153_A specify a louvered door with minimum 16 square feet free area for return air path (Keynote 5), while sheet M153_B specifies a louvered door with minimum 1.5 square feet free area for the same purpose (Keynote 7). This represents a 10x difference in the required free area specification for return air doors between the west and east residential plans that reference each other for continuation.
Dryer Exhaust Discharge Located Too Close to Outside Air Intake
The roof plan shows the 'DRYER EXHAUST' discharge point located immediately adjacent to the 'OA SUPPLY DOWN TO LAUNDRY ROOMS' intake. Based on the drawing scale (1/8" = 1'-0"), the separation between these two penetrations appears to be significantly less than the required 10 feet.
Generator Scope Conflict (Permanent vs Temporary)
E402 Plan 14 (Roof) depicts a permanent 'GENERATOR' installation with a 'NEMA 3R ATS-UH-1'. The Plan Notes on E402 further confirm a permanent setup by specifying connections for a 'GENERATOR BATTERY CHARGER' and 'GENERATOR BLOCK HEATER'. However, the E501 Riser Diagram text describes a 'TEMPORARY GENERATOR TERMINATION BOX', which implies a connection point for a portable generator and contradicts the permanent generator and ATS shown on the enlarged plans.
Inconsistent Breaker Sizing for Amenity Heat Pumps
The Mechanical Split System Schedule specifies Maximum Overcurrent Protection (MOP) ratings of 30A and 40A for Amenity Outdoor Units AAHU-3, AAHU-5, and AAHU-2. However, the Electrical Panel 'AMR' (Amenity Roof) schedule provides 50A breakers for all associated circuits (AMR1-2 through AMR1-5), which exceeds the maximum allowable protection size for these units.
Conflicting Outdoor Air Intake Separation Distance
There is a direct contradiction in the required separation distance between outside air intakes and exhaust discharges. Drawing M153_A and M153_B specify '10'' (10 feet), which aligns with typical code requirements, while Drawing M154_A specifies '10"' (10 inches), which is significantly less and likely a code violation.
Panel M4 Main Rating Conflict with Feeder Breaker
The Distribution Panel MDP1 Schedule lists Circuit 10 feeding 'PANEL M4' with a 250 Amp trip breaker. However, the Panelboard Schedule for M4 specifies a 'MAIN 100' rating. Feeding a 100A rated panel with a 250A breaker violates code unless the panel has a 100A main breaker (not indicated in schedule headers) or is specifically rated for the feed.
Sample High Priority Findings (10 Total)
Mechanical notes specify 2015/2012 IMC instead of complying with current (2018) IMC requirements
The sheet's general notes and basis-of-design notes direct installation/design to older IMC editions (2015 IMC and IMC 2012). The applicable mechanical code requirements for refrigeration and hydronic systems are those of the currently adopted code (2018 IMC) and its chapters govern the work. Referencing older IMC editions is a direct contradiction to complying with 'this code.'
Non-Compliant Refrigerant Piping Joint Specification
The general notes for the refrigerant piping shaft require that 'ALL WELDED COPPER SHALL BE WIPED AT ALL JOINTS.' This instruction is technically incorrect and violates code standards. 'Wiped' joints are an obsolete method used for lead piping and are not permitted for copper refrigerant piping. IMC Section 1107.1 requires piping design to accord with ASME B31.5, which mandates brazed joints (or approved mechanical joints) for refrigerant applications.
Missing Gas-Tight Shaft Specification
Detail 9 depicts a refrigerant piping shaft connecting multiple floors (1st through 7th). The detail specifies the shaft construction as 'INSULATED, FIRE RATED SHAFT ENCLOSURE'. However, IMC Section 1107.2.2 Exception 5.1 explicitly requires that refrigerant piping penetrations connecting separate pieces of equipment in non-industrial occupancies be enclosed in a 'gas-tight, fire-resistive duct or shaft'. The drawing specifies fire-rating but fails to specify the required gas-tight construction, which is critical for preventing refrigerant migration into occupied spaces during a leak.
Refrigerant Piping Prohibited in Fire-Resistance-Rated Corridor
Detail 11 ('TYPICAL CORRIDOR AHU DETAIL') clearly depicts 'REFRIGERANT PIPING TO OUTDOOR UNIT' connecting to an air handling unit located within the corridor (indicated by the detail title and the '2 HR FIRE RATED WALL' reference typical of exit access corridors). The Building Code Section 1107.2 explicitly prohibits placing refrigerant piping in a fire-resistance-rated exit access corridor.
Prohibited Recirculation from Demo Kitchen
The drawing shows a 'DEMO KITCHEN' (Room 01-107) connected to the mechanical distribution system. IMC Section 403.2.1 Item 3 prohibits the recirculation of air from spaces where mechanical exhaust is required. Kitchens require mechanical exhaust per Table 403.3.2.3. The plan shows supply air provided to the space and a transfer duct connecting it to the adjacent corridor/lounge return path, with no dedicated exhaust system visible. Therefore, air from the Demo Kitchen appears to be recirculated to other spaces via the common HVAC unit, which is a code violation.
Value Delivered
"Finding 167 issues before permit submission prevented months of delays and costly rework. The missing fire dampers and unprotected refrigerant risers alone would have failed inspection, and the mechanical ventilation gaps would have required major redesign during construction."
— Project Team