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Building Code Reference

Got a CMC 802.6.1 correction?

Gas vent termination

For builders in California, Greater Seattle, the Las Vegas area, the Denver area and Kansas City · CrossBeam Permits

What this code requires, how to fix it, and how cities and counties review it

What this code requires

CMC 802.6.1 is the California Mechanical Code section that sets where gas vents terminate. A listed-cap vent 12 inches or smaller and at least 8 feet from a vertical wall terminates at the roof-pitch height in Table 802.6.1; larger vents or vents closer to a wall must end at least 2 feet above the roof penetration and 2 feet above anything within 10 feet. Through-the-wall terminals follow the clearances in CMC 802.8 and Table 802.8.1, and chimneys follow 802.5.4. Furnaces, water heaters, boilers, and direct-vent fireplaces are the most common permits flagged.

How to fix it

  1. Pull the applicable termination rule from CMC 802.6.1 or 802.8

    In the 2025 CMC, 802.5 covers chimneys; gas vents terminate per 802.6.1 and through-the-wall terminals per 802.8. A listed-cap gas vent 12 inches or smaller and at least 8 feet from a vertical wall uses Table 802.6.1, which sets height by roof pitch. Direct-vent and other wall terminals use the clearances in Table 802.8.1. Write down the specific rule and the required dimensions — you will call these out on the plans in the next steps.

  2. Dimension the vent termination height above the roof

    On the roof plan or the building section, add a callout showing the vent pipe termination height above the roof. Vents over 12 inches, or within 8 feet of a vertical wall, must terminate at least 2 feet above the highest point where they pass through the roof and 2 feet above any part of the building within 10 feet; smaller vents use Table 802.6.1 by roof pitch. Label the dimension in inches, include an arrow pointing to the termination, and note the CMC table number you are referencing. A single clear callout eliminates most plan-check questions on this section.

  3. Show clearances from windows, doors, and openings on the elevation sheet

    On the exterior elevation sheet, draw a dashed line from the vent terminal to each nearby window, door, and gravity air inlet within the clearance zone. Dimension each gap. CMC Table 802.8.1 sets these clearances: 6 to 12 inches from an openable window or door for direct-vent terminals by input, 4 feet below or beside (1 foot above) for non-direct terminals, and 10 feet horizontally or 3 feet above a mechanical air inlet. If your site is tight and a clearance looks marginal, add a note stating the measured distance and the code minimum. Plan-checkers approve details that show the work was done — leaving it to the reviewer to calculate guarantees a comment.

  4. Detail the direct-vent exterior-wall terminal if applicable

    For direct-vent appliances terminating through an exterior wall instead of the roof, add a detail on the exterior elevation showing the concentric terminal location, its height above grade (minimum 12 inches above finished grade, porch, or deck), its clearance from nearby openable windows and doors, and any corner clearance the manufacturer specifies (Table 802.8.1 sets none of its own). Note the terminal model or manufacturer if it is a manufacturer-listed assembly, because some local AHJs want confirmation that the terminal is listed for the appliance. A 1/4 inch = 1 foot detail callout on A3 or M2 works well.

  5. Address chimney cap or spark-arrestor restrictions for masonry vents

    If the vent is a chimney or a gas vent with a cap or shroud, draw a detail of the termination. Vents may not discharge into a space enclosed by screens with openings smaller than 1/4 inch (CMC 802.1.2), and decorative shrouds are not allowed unless listed for that system (CMC 802.5.4.3). A fine bird screen or unlisted decorative cap is a common flag. Note the mesh size and the cap or shroud listing so the plan-checker can verify it at a glance.

  6. Cross-reference the mechanical schedule to the sheet showing the termination

    Add a note in the mechanical equipment schedule pointing to the sheet and detail number where the termination callout lives. Something like Vent termination per CMC 802.6.1 — see A3/detail 4. This cross-reference prevents the plan-checker from approving the mechanical sheet and then flagging the architectural sheet separately. It also helps on re-submittals: the reviewer can jump directly to the corrected detail without hunting through the set.

  7. Write the correction response letter citing the specific sub-section

    When you respond to a vent termination comment, title your response with the exact comment number and code reference. State which table row applies to your appliance, the required dimension, and what the revised plans show. Reviewers on tight schedules skim response letters first and then verify in the drawings. A response that matches the comment number to a specific plan sheet and detail number closes the loop cleanly and reduces the chance of the same comment coming back on the next cycle.

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Why you got flagged

Here is why plan-checkers flag CMC 802.6.1 most often on residential gas-appliance permits.

The most common reason is that the vent termination height above the roof is not called out on the mechanical plans at all. If the sheet just shows a vent pipe symbol exiting the roof without a dimension or a note referencing the code table, the plan-checker has no way to verify compliance and will flag it. This happens most on water-heater replacements where the contractor is working off an existing roof penetration and assumes the prior installation was correct.

A second scenario is clearance from openings. A roof vent has to end at least 3 feet above a forced air inlet within 10 feet (CMC 802.6.1), and a through-the-wall terminal has to meet the window, door, and air-inlet clearances in Table 802.8.1. In dense urban lots with two-story additions, the vent from a first-floor furnace can end up uncomfortably close to a second-floor bedroom window. If the elevation sheet does not show those clearances explicitly, expect a flag.

Chimneys and caps get flagged on a different sub-issue. A chimney for residential-type appliances must extend at least 3 feet above the roof penetration and 2 feet above any part of the building within 10 feet (CMC 802.5.4). Gas vents must end in a listed cap or listed roof assembly, decorative shrouds are allowed only where listed for the system, and vents cannot discharge into a space enclosed by screens finer than 1/4 inch. Sketching the cap detail saves a round of questions.

Direct-vent appliances have their own column in CMC Table 802.8.1, with clearances for the wall terminal that scale with appliance input. These often terminate through an exterior wall rather than the roof, which catches contractors off guard. If the floor plan shows the appliance but the exterior elevation does not mark the terminal location and its clearance from grade, the correction will ask for it.

The official code

2025 California Mechanical Code Section 802.6.1 Gas Vent Termination and Section 802.8 Through-the-Wall Vent Termination, via California Building Standards Commission

Read the source →

Common questions

What is the minimum vent termination height above the roof under CMC 802.6.1?
It depends on the vent size and how close it is to a wall. A gas vent with a listed cap, 12 inches or smaller and at least 8 feet from a vertical wall, uses Table 802.6.1: 1 foot above the roof from flat up to a 6/12 pitch, rising with slope to 4 feet at 12/12. A vent over 12 inches, or within 8 feet of a wall, must end at least 2 feet above where it passes through the roof and 2 feet above any part of the building within 10 feet. A Type B or Type L vent must also end at least 5 feet above the highest connected draft hood or flue collar. Sidewall direct-vent terminals follow Table 802.8.1 instead, with clearances from grade and openings rather than roof pitch.
Does CMC 802.6.1 apply to water heater replacements or only new installs?
Yes, CMC 802.6.1 applies to water-heater replacements whenever the permit requires plan check. In most California cities, a water-heater replacement below a certain BTU threshold qualifies as an over-the-counter permit and skips plan check. But if the replacement involves a new vent run, a change in appliance category, or an upgraded unit above the OTC threshold, plan review kicks in and the vent termination must be shown on the submitted plans. Check your city OTC permit matrix before assuming a replacement is exempt from plan check.
Can a direct-vent furnace terminate through the garage wall?
Through the garage's exterior wall to the outside, yes; into the garage, no. CMC 802.3 requires venting systems to convey all flue and vent gases to the outdoors, so a terminal that discharges into an attached garage or other enclosed space does not comply, and the exhaust would create a carbon monoxide hazard. A direct-vent furnace installed in a garage can terminate through the garage exterior wall, keeping the Table 802.8.1 clearances: 12 inches above grade and the openable window and door clearance for its input rating, including windows on the main structure. Show the terminal on the exterior elevation of the garage, not on the interior floor plan.
My corrections letter says the vent is too close to a window — how much clearance do I need?
It depends on the terminal type. For a through-the-wall terminal, CMC Table 802.8.1 sets the clearance to an openable window or door. Direct-vent terminals need 6 inches for appliances up to 10,000 Btu/hr, 9 inches up to 50,000 Btu/hr, and 12 inches up to 150,000 Btu/hr. Non-direct terminals need 4 feet below or to the side of the opening, or 1 foot above it. Any terminal needs 10 feet horizontally or 3 feet above a mechanical air supply inlet. A roof vent must end at least 3 feet above a forced air inlet within 10 feet. If your site is tight, the fastest fix is often relocating the termination rather than arguing for a reduced clearance.
Does CMC 802.6.1 require a screen or cap on the vent termination?
Yes. CMC 802.6.1 requires every gas vent to extend through the roof flashing, roof jack, or roof thimble and terminate with a listed cap or listed roof assembly. Decorative shrouds are not allowed unless they are listed for that specific venting system and installed per the manufacturer's instructions. Vents also cannot discharge into a space enclosed by screens with openings smaller than 1/4 inch (CMC 802.1.2), so a fine bird screen or unlisted decorative cap can fail even if it is at the correct height. On plan submittals, show the cap detail and note its listing.
Do I need to show vent termination on both the mechanical plan and the roof plan?
Technically you only need to show it once, but showing it on both is the cleaner approach. The mechanical plan establishes which appliance connects to the vent and what category it is. The roof plan or building section shows the actual height dimension. A cross-reference note on the mechanical schedule pointing to the roof plan detail prevents the plan-checker from approving one sheet and flagging the other separately, which costs you another review cycle.

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