Refs: IMC 306.1-306.2.
Plain English:
306.1 Access: Every energy-using appliance/control/heat exchanger must be serviceable without removing permanent construction, fire-rated assemblies, or unrelated piping/ducts/equipment. Provide a level working space 30 in x 30 in at the control/service side.
306.2 Appliances in rooms: Rooms with appliances need a door and an unobstructed passage 36 in wide x 80 in high.
Dwelling exception: You may use a 24 in passage only if (a) the opening/route is large enough to remove the largest appliance, and (b) a level service space 30 in deep with height = appliance height (but >=30 in) exists at the front/service side with the door open.
On Plans: Why It Matters
This is an inspection gate. If a tech must tear into walls/duct/other systems to reach or replace a unit-or if the 30x30 and passage/door aren't there-you'll get redlines, delays, and change orders. Clear access also reduces service injury risk and warranty disputes.
🧾 Where To Show It (sheet map)
M-001: "Provide 30x30 level service space at control side per IMC 306.1. No removal of permanent construction or unrelated systems to service/replace. Rooms: 36 in x 80 in passage. Dwelling exception: 24 in passage allowed only with verified removal path and 30x30 at the unit."
M-101/... (Plans): Draw/dimension the 30x30 box; show door swing and passage width; trace the removal path to an exit/hoist point.
M-501/502 (Details): Standard service-clearance envelope detail; example removal-path diagram.
M-601 (Schedules/Notes): Columns: Service Side, 30x30 Provided (Y/N), Passage Width (in), Largest Appliance Removal Path (Y/N).
Code Path: Service Clearance Documentation
Drawings must show required access dimensions for each major piece of mechanical equipment - not just the unit footprint, but service clearances on all sides and above.
For rooftop units: show the roof access hatch or permanent ladder and the service platform or walkway to each unit on the roof plan.
Service clearances on M-101/M-102 must be shown as dimensions, not just as notes - reviewers verify dimensional compliance.
Check: Clearance Verification
Confirm service clearances on the equipment plan match minimums: 30 in on the service/access side for most equipment, 18 in on non-service sides - or the listing requirement if more.
For equipment above accessible ceilings or in mechanical rooms, confirm no structural members, ductwork, or piping are shown in the service clearance zone.
Rooftop equipment plan must show the access hatch (minimum 22x30 in) and its location relative to the unit.
Review Risk:
Service and replacement paths can be lost when adjacent structure, ducts, piping, ceilings, or electrical equipment are coordinated later.
Rooftop equipment without a drawn access path (hatch, ladder, walkway) is a pre-occupancy hold - show the access path on the roof plan, not just a general note.
Equipment in mechanical rooms that encroaches on required electrical service clearances is a common mechanical-electrical coordination gap.
Field Tip:
Place a "30x30 at control side" callout on every unit.
Verify the removal path (width/height clear) through doors/turns-no "remove duct" steps.
Using the 24 in dwelling exception? Document both the removal path and the 30x30 service space with the door open.
Masterbuild QA Lens
Access is the single most cited Ch3 inspection failure. For 306.1-306.2: every energy-using appliance must have a drawn access path 36 in wide and 80 in high to a door with a threshold <=24 in. Confirm it on the floor plans. Do not leave access compliance to the field.
Drawing / Submittal Check
Show the Section 306 access, working-space, removal-path, room/attic/underfloor/roof condition, and applicable listing/manufacturer service clearances. Do not assume one generic clearance applies to every side or installation type.
Common Review Risk
The plan reserves a nominal footprint but not the three-dimensional service and removal path. Verify the final coordinated condition before adjacent work is installed or concealed.
When To Escalate
Escalate when the required service clearance for a large piece of equipment cannot be achieved in an existing mechanical room without removing another piece of equipment, and the removed equipment must remain in service during the renovation. Equipment replacement in occupied, operating mechanical rooms requires a phased shutdown and startup plan agreed upon by all parties before construction starts.
Rated Assembly Coordination
Access and service space requirements may require openings through rated assemblies to reach equipment. Show access panel type, fire rating, and UL listing for every panel that penetrates a rated wall or ceiling in the service space detail.
Load Assumption Check
Service space clearances affect equipment placement, which affects equipment sizing if the available space constrains unit selection. Confirm that the selected equipment fits within the code-required clearances and that clearance-driven layout changes don't require a load recalculation.