Spot the Violation

FramingFire separation, egress & alarmsLevel 32018 IRC

Basement ceiling below a bathroom wall

Looking straight up at an unfinished basement ceiling. Sawn 2x10 floor joists run up and down the frame and bear on a steel beam across the top, with OSB subfloor above them. In the middle bay, a row of penetrations comes down through the subfloor and the wall plate above in a line. A yellow cable and a white cable come through small holes packed with orange foam. Red and blue PEX lines come through holes packed with the same orange foam. A 1-1/2 in. white PVC drain comes through a hole sealed with orange foam. A 3 in. white PVC pipe printed 3 IN PVC DWV comes down through a larger, ragged hole with a dark gap all the way around it and then turns with a long-sweep elbow to run down the bay. A clamp work light hangs from a joist. 3 IN PVC DWV ASTM D2665
Unfinished basement ceiling under a first-floor bathroom

What's wrong here?

  1. The gap around the 3 in. pipe where it passes up through the floor and wall plate is not fireblocked
  2. The cable and PEX holes must be sealed with fire caulk; foam is not allowed
  3. The joist bays need fireblocking every 10 ft along their length
  4. Nothing. This installation is compliant
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Show the answer and the code reference

The answer

The annular gap around the 3 in. DWV pipe where it passes through the subfloor and the bottom plate of the wall above is left open. R302.11 requires openings around pipes at floor and ceiling level to be fireblocked.

Correct choice: 1. The gap around the 3 in. pipe where it passes up through the floor and wall plate is not fireblocked

A wall cavity that opens straight into the basement through an oversized pipe hole acts as a chimney. A basement fire (furnace, dryer, storage) sends flame and smoke up the stud bay and into the floor or attic above, out of sight. R302.11 item 4 requires fireblocking at openings around vents, pipes, ducts, cables and wires at ceiling and floor level, using an approved material that resists the free passage of flame and products of combustion. This crew sealed the cables, the PEX and the 1-1/2 in. drain but missed the biggest hole, the one around the 3 in. stack. Inspectors find this in nearly every house, usually at the stack, because the hole saw is oversized and the pipe goes in after the other trades have sealed theirs.

How to fix it

Pack the gap around the 3 in. pipe with an approved fireblocking material, such as a fireblocking foam sealant or fire caulk backed with mineral wool, from below and, if accessible, from above at the plate. Keep the sealant compatible with PVC per the manufacturer. Then check the rest of the floor for missed penetrations before the ceiling is covered.

Code references

  • IRC 2018 R302.11 — Fireblocking

    In combustible construction, fireblocking must cut off concealed draft openings, vertical and horizontal, and form an effective fire barrier between stories and between a top story and the roof space. Item 4 requires it at openings around vents, pipes, ducts, cables and wires at ceiling and floor level, with an approved material that resists the free passage of flame and products of combustion; the annular fill need not meet ASTM E136.

    Drills citing R302.11

  • IRC 2018 R302.11.1 — Fireblocking materials

    Except for the annular fill allowed by R302.11 item 4, fireblocking must be an accepted material such as 2 in. nominal lumber, 23/32 in. wood structural panel, 1/2 in. gypsum board, or mineral wool or glass fiber batts or blankets securely retained in place. Loose-fill insulation is not accepted as fireblocking unless tested for it.

    Drills citing R302.11.1

2024 IRC:not yet checked Confidence: low

Minnesota

MN adopts this rule as writtenConfidence: medium

Minnesota adopts the 2018 IRC with Minnesota amendments as the Minnesota Residential Code (Minn. Rules ch. 1309). No Minnesota amendment to R302.11 is known. DLI is adopting the 2024 IRC as the next edition; see the 2024 IRC note.

About the Minnesota Residential Code

Why the other choices are wrong

  • The cable and PEX holes must be sealed with fire caulk; foam is not allowed. R302.11 item 4 asks for an approved material that resists the free passage of flame and smoke, and the annular fill does not have to pass ASTM E136. A fireblocking foam sealant (usually orange) is commonly accepted for this.
  • The joist bays need fireblocking every 10 ft along their length. The 10 ft rule in R302.11 item 1 is for concealed spaces in stud walls and furred spaces. This open basement ceiling is not a concealed space, and draftstopping under R302.12 applies only to concealed floor-ceiling spaces with usable space above and below.
  • Nothing. This installation is compliant. Every other penetration in the row is sealed, but the 3 in. stack's oversized hole leaves an open path from the basement into the wall cavity above, which R302.11 requires to be fireblocked.
Safety hazardLevel 3 · Master#fireblocking#penetration#basement#plumbing#annular space

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