A frame, wall or ceiling?

[Mr. Inspector]

Reviewing a A frame house plan. Designer is using ResCheck 2018 IECC for insulation. they are calling the A frame side walls/roof "wall sloped". Shouldn't it be labeled "ceiling"?

 

[mtlogcabin]

The IRC and the IECC do not have a definition of an exterior wall that would help answer your question. However the IBC definition should help clarify how to label, for energy code compliance, if you are dealing with a wall or ceiling assembly.

2018 IBC
[BF] EXTERIOR WALL. A wall, bearing or nonbearing, that is used as an enclosing wall for a building, other than a fire wall, and that has a slope of 60 degrees (1.05 rad) or greater with the horizontal plane.

 

[e hilton]

I would ask what the outer surface is … fiberglas roof shingles? … metal roof sheets? … it’s a roof.

 

[steveray]

The IRC and the IECC do not have a definition of an exterior wall that would help answer your question. However the IBC definition should help clarify how to label, for energy code compliance, if you are dealing with a wall or ceiling assembly.

2018 IBC
[BF] EXTERIOR WALL. A wall, bearing or nonbearing, that is used as an enclosing wall for a building, other than a fire wall, and that has a slope of 60 degrees (1.05 rad) or greater with the horizontal plane.

And to complete the code path...

R201.3 Terms defined in other codes. Where terms are not
defined in this code such terms shall have the meanings
ascribed in other code publications of the International Code
Council.

 

[Yikes]

I would ask what the outer surface is … fiberglas roof shingles? … metal roof sheets? … it’s a roof.

I've seen a number of walls, particularly on "french mansards", that are clad with shingles.

 

[Mr. Inspector]

I wantes to know what ResCheck defined as and got his, about what IBC says:

Question:
I am reviewing a plan for an A frame house. The designer used "wall sloped: wood frame, 16" o.c. on the ResCheck for the slanted roof. Shouldn't it be ceiling?

Response:
There may not be a definitive answer in the codes, although you probably could make a pretty strong argument for a 60-degree cutoff—i.e., an A-frame element sloped less than 60 degrees from the horizontal would be a roof/ceiling, 60 degrees or more from horizontal a wall. This is based on how the IECC distinguishes skylights from regular (vertical) fenestration: "Glass or other transparent or translucent glazing material installed at a slope of less than 60 degrees (1.05 rad) from horizontal." Since skylights are usually parallel with the roof they’re embedded in, and vertical fenestration parallel with the wall, our codes team has indicated that you can make that case.

Thanks,
BECP Technical Support


. Had to find a protractor to check the plans. I usually think that if has shingles it’s a roof. Found out that these A frame walls are 65 degrees. So it’s a wall.

Now since it’s not defined as a wall it does not need to comply to Chapter 9 Roof Assemblies but per R703 Exterior Wall Covering?

House wrap instead of ice & water shield and underlinement?

 

[e hilton]

I've seen a number of walls, particularly on "french mansards", that are clad with shingles.

True, but that building also has a flat roof, and the mansard walls appear to be far steeper than 60*.

 

[bill1952]

I don't think cladding materials are a good measure of it being a wall or roof. Consider a house with cedar shingles on walls and roof. And lots of buildings with metal walls and roofs. The 60° is objective and somewhat performance based.

 

[tmurray]

60 degree threshold is used in Canadian codes as well, so there must be some logic behind it.

 

[steveray]

Are there metric degrees in Canada?

 

[Joe.B]

I was told by an architect that they look at walls and ceilings as more of a gradient than an absolute. The two extremes are if it's vertical it's a wall, if it's horizontal its a roof. Anything in between has characteristics of both. If the "roof" pitch is very shallow it is most like a roof, and not much like a wall. If it's very steep, like in the example given here, it's much more like a wall than a roof. I know that doesn't really help answer the question, but I appreciated the different way of thinking about it.

 

[tmurray]

Are there metric degrees in Canada?

No, but it would make sense. Where metric uses a base ten system, it would be logical for degrees to use it as well...

 

[Mr. Inspector]

So what if there was a regular house with a flat ceiling and a attic with a steep sloped roof of over 60 degrees in climate zone 5:
If insulating ceiling it would need to be R49.
If insulating the roof it would only need to be R21?