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Old 03-30-2012, 10:22 PM   #1
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question on IRC Table R803.5.1(9)


This IRC table is named Rafter/Ceiling Joist Heel Joint Connections. Anyone know exactly what that's trying to prescribe? I thought I knew until I saw the table cell that says 39 fasteners are needed at the rafter-joist connection of a 3:12 roof (with 70psf ground snow load and a 36' roof span). Seriously? 39 16d common nails at a joint? Considering a nail should be no closer than half its length to another nail, is 39 nails even possible???). I'm assuming I'm just not understanding the table correctly.

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Old 03-31-2012, 01:37 AM   #2
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question on IRC Table R803.5.1(9)


Oh, I suppose you could say that it is excessive but, the drawing shows 3/12 pitch with Roof Rafter @ 2 x 10 and Ceiling Joists @ 2 x 10.
So the low intersection between the two should allow for that many nails.

You know they are calling out for a rafter span of 36' (feet) right?

Andy.
P.S. it is section 802.5.1 not 803.
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Old 03-31-2012, 09:38 AM   #3
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question on IRC Table R803.5.1(9)


Nice! You made a believer out of me. In fact, you inspired me to fire up my CAD program. I calculated the potential for a whopping 75 nails, spaced 3/4" from the edge, and 1-1/2" from each other, in that triangular area. So indeed it is possible. Thanks! BTW, the table number I referenced is in the 2006 IRC. My bad for not mentioning the year.
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Old 03-31-2012, 12:51 PM   #4
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question on IRC Table R803.5.1(9)


Thirty nine nails might sound like a lot of nails if not taken in the context of the shallow roof slope and the heavy live load.

The shallower the rood slope, the larger the horizontal thrust there is to be resisted by the ceiling joists through that nailed connection.

A 70 psf live load is a large live load. A 70 psf live load is about the same live load required for automobile parking decks in some locations.
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