Habitable Attic

[jar546]

Under what conditions does an attic space qualify as a "habitable attic" according to the IRC, and what are the specific requirements for ceiling height and egress in such spaces?

A homeowner wants to convert their attic into a bedroom. The existing attic has a sloped ceiling that reaches 7 feet at the peak but drops to 4 feet at the exterior wall. There is a window on one end of the attic, but it doesn't fully meet the size requirements for emergency escape and rescue openings as outlined in Section R310.

The homeowner argues that the majority of the attic space meets the 7-foot requirement, with the lower areas being used for storage. The inspector, however, insists that the habitable portion of the space must meet the minimum ceiling height requirements, which could mean more of the area needs to be evaluated or altered.

The homeowner believes the existing window is sufficient for emergency escape, while the inspector requires a larger, code-compliant window to be installed, which would involve significant structural changes.

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[Yankee Chronicler]

Without seeing a plan and a cross-section, I am inclined to agree with the inspector. If the sloped ceilings only reach a height of 7 feet at the peak, then NONE of the space has the required ceiling height.

From the 2021 IRC Commentary for the definition of "Attic, Habitable":

The code allows that an attic can contain habitable space. In such cases, the attic is not required to be considered as a story. Note that there is no limitation given for the area of the attic that contains habitable space. The intent is that the habitable space is to fit within the roof area of the story below without the use of knee walls, such as a bonus room that fits within a roof truss above a garage. See the commentary to Section 326.

So then we look at IRC 326, which includes 326.2:

R326.2 Minimum dimensions. A habitable attic shall have a floor area in accordance with Section R304 and a ceiling height in accordance with Section R305.

The Commentary for 326.2 says:

The habitable attic must meet the same minimum floor dimensions as a room of at least 7 feet by 7 feet. The attic can have sloped ceilings, but the floor area with a ceiling height of less than 5 feet cannot count toward the required floor area. Section R305.2, Exception 1 states that attics can have a ceiling height of 5 feet to 7 feet for up to 50 percent of the room as long as the ceiling height is 7 feet or greater for the rest of the room. This does not require that areas with a ceiling height less than 5 feet be walled off, just that the space and height limitations be applicable to the required room area.

Without knowing the actual dimensions and the slope of the roof/ceiling, we can't definitively answer the question.

 

[jar546]

Without knowing the actual dimensions and the slope of the roof/ceiling, we can't definitively answer the question.

If the room is 16" wide (not the gable end) you can figure it all out.

 

[Yankee Chronicler]

There's nothing to figure out. The requirement is that at least 50% of the room has to have a ceiling height of 7 feet. You wrote that the peak is 7 feet. That means 100% of the room has less than 7 feet of headroom, so it's not allowed as a habitable attic.

 

[tmurray]

Canadian Code:

It's a change in use, so it would have to meet current code.

Window size has to meet.
The minimum height must be met for the minimum area of the room, but if the room is bigger than the minimum area, the rest of the space doesn't have to meet.