# Table 602 - Rating required for entire wall?



## MNI55 (Jan 30, 2018)

I have a IIB building in which a portion of the exterior wall has a fire separation distance of less than 10 feet. Am I correct thinking the portions of the exterior wall where the fire separation distance is less than 10' require a 1 hour rating where the portion of the wall with a FSD greater than 10 do not require a rating (say around the corner). The view above appears to be supported by a older version of the IBC handbook but not directly spelled out in the code that I have seen.

Thanks in advance for your thoughts.


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## steveray (Jan 30, 2018)

FIRE SEPARATION DISTANCE. The distance measured
from the building face to one of the following:
1. The closest interior lot line;
2. To the centerline of a street, an alley or public way; or
3. To an imaginary line between two buildings on the
property.
The distance shall be measured at right angles from the
face of the wall.

It is measured square off of the exterior building wall....unless it is a really odd shaped building, around the corner shouldn't matter...


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## classicT (Jan 30, 2018)

steveray said:


> The distance shall be measured at right angles from the
> face of the wall.
> 
> It is measured square off of the exterior building wall....unless it is a really odd shaped building, around the corner shouldn't matter...



Should be measured perpendicular to the property line/centerline/etc. If you consider a wall that is not parallel to the property line, then the setback would be somewhat less than called for if measuring 90-degrees from face of wall.


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## YongMNLad (Jan 30, 2018)

Here is the 2012 commentary. I believe what you are asking is the difference between the red and blue highlighted portions of the wall?

My understanding is that the imaginary line continuous passed the other building and the FSD does not change along the wall.


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## MNI55 (Jan 30, 2018)

Essentially my question is that if say the North wall requires a rating East, West, South walls of the building are evaluated based on their own fire separation distance. The North Wall Fire rating requirement does not impose the requirement on the other three walls. This may be an obvious answer but its not directly worded this way in the code that I can see.


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## classicT (Jan 30, 2018)

You are correct in your understanding


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## steveray (Jan 31, 2018)

Draw the FSD line, and then measure perpendicular off of the buildings to it....It's that simple, the line can bend and curve to whatever makes it easier, but the line has to be there...


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## classicT (Jan 31, 2018)

steveray said:


> Draw the FSD line, and then measure perpendicular off of the buildings to it....It's that simple, the line can bend and curve to whatever makes it easier, but the line has to be there...


Perpendicular to the FSD line, not from the building


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## steveray (Jan 31, 2018)

Ty, I posted the code section in post 2....The distance shall be measured at right angles from the
face of the wall.


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## Builder Bob (Jan 31, 2018)

Be careful, or a checker board approach to building houses/buildings on the lot will occur with corners touching and never having to rate any walls because the FSD was measured at 90 degrees to the face of the wall. Interpretation (as allowed by the code by the building official) need to include an arc at the corners so that the following design could not be presented.... if no walls are within 10 feet of the face of the wall at 10 feet, isn't this possible?



	

		
			
		

		
	
For what it is worth, fire radiates in a circular or cone shape when blowing out of a window, thus a window at the corner could allow direct flame contact with the side wall of the adjacent corner.... fire or flames don't just travel in a straight line ---- if it did , why doesn't a candle flame appear more blocky in shape instead of a tapered cone as it is burning.


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## steveray (Feb 1, 2018)

BB....The FSD line would have to run between the buildings somewhere and in that situation would have to touch them if it were a true checkerboard, so it would not fly....


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## Builder Bob (Feb 5, 2018)

The distance shall be measured at right angles from the
face of the wall.

Can't measure off the face of the corner


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## steveray (Feb 5, 2018)

Correct, but the only way you would get out of it for one building would to be to put the FSD line on the exterior wall of the other building which would raise the requirements on that one.....


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## Builder Bob (Feb 6, 2018)

I did ---- FSD @ 90 degrees to face of wall creates a void in the corners as depicted...... AHJ has to make the interpretation that a 10 foot arc exists at the corners.....not in the code book.


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## steveray (Feb 7, 2018)

You measure at right angles from both buildings to the FSD line, not to the other building, unless the FSD line is on the other building, which would be a 0 FSD for that building with all of those restrictions. Which protects the other building by default...Draw a line at 45 degrees through the corner(s) and in theory, yes, at the corners, there is a flaw, but 1 inch away from the corner there is not....The problem self regulates IMO...


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## steveray (Feb 7, 2018)

Best thing I can find (not surprising) is a firewall discussion from Ron...

http://specsandcodes.typepad.com/.a/6a01538e3cb98f970b015393d09431970b-popup

Firewall creates separate buildings and therefore a FSD line has to be created. This is why the openings on either side of a firewall get away without a rating if the line goes straight out....


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