The garage ceiling beneath the bedroom is covered with 5/8-inch Type X gypsum board and the wall between the garage and the house is covered on the garage side with 1/2-inch gypsum board. The steel beam and the two steel columns that carry the garage ceiling framing are left completely exposed in the garage with no covering of any kind. How should the inspector rule?
- Issue a correction: the structure supporting a required separation assembly must itself be protected with not less than 1/2-inch gypsum board or an equivalent, so the beam and the columns have to be covered
- BAccept it: structural steel is a noncombustible material that will not add fuel to a fire, so the beam and the columns need no covering and the gypsum board on the ceiling and the wall completes the separation
Noncombustible is not the same as fire-resistant. Unprotected structural steel loses a large share of its strength at temperatures a car fire reaches easily, which is why the structure supporting a separation is protected.
- CAccept it: the requirement addresses the ceiling and wall membranes only, so members that pass through or carry those membranes are left exposed the way the tested assemblies show them
The membranes are the visible part of the requirement, but the structure supporting them is expressly included. Leaving beams and columns bare lets the separation fall in a fire while both of its faces are still intact.
- DIssue a correction requiring the beam and the columns to be covered on all faces with 5/8-inch Type X gypsum board, matching the material used on the garage ceiling under the bedroom
Type X on all faces exceeds what the code asks of the supporting members, which is not less than 1/2-inch gypsum board or an equivalent. Writing the heavier requirement invites an appeal the department will lose.
Why A is correct
The provision reaches past the membrane to the structure carrying it. Beams, columns and posts supporting a required separation assembly must be protected with at least 1/2-inch gypsum board or equivalent. Exposed steel in a garage fire softens and deflects while the ceiling above it is still intact, which defeats the entire separation.
What this question is testing
The item tests whether the candidate extends the garage separation requirement to the structure supporting the assembly, knows the level of protection required on that structure, and understands why a noncombustible material still needs protection.
On the job
Garages with living space above almost always have a flush beam or a pair of columns, and the drywall contractor treats them as trim rather than as part of the separation. Look up at the beam and down at the column base at the framing and drywall inspections. Also check that the column protection continues to the floor and that the ceiling membrane is properly fastened, since a beam wrapped neatly but a ceiling screwed at 24 inches on center is still a failure.
Memory technique
A protected ceiling on a bare beam falls with the beam.
Exam tip
Protect the membrane and whatever holds the membrane up.
Where to look it up
IRC Chapter 3, fire-resistant construction, the garage separation section including the sentence on supporting structures.