How to properly sister rafters/joists in my attic (pic)
#1
10-05-10, 07:11 PM
How to properly sister rafters/joists in my attic (pic)
Here's a pic of my attic:
Imageshack - img5813s.jpg
Counting the rafters/joists from left to right, number them #1, #2, #3, #4, #5.
I'm going to cut #3 & #4 (both rafters/joists) to install a 44 1/4" wide (rough opening) skylight. I need to double-up joists & rafters #2 and #5
My questions are:
1. Can I double-up rafter #2 by adding a new one to the RIGHT of it? As you can see, it would not be able to be a "full length" rafter like the existing #2 is because joist #2 is "in the way"....so the rafter would have to "rest" on joist #2, is that ok? Or do I NEED to double-up to the left of the existing rafter with a full-length 2x6?
2. I need to double-up joist #2 to the LEFT of it, otherwise my rough opening for the skylight will be compromised. How can I double-up joist #2 to its left? Can I add 2 2x6's, one that won't be full length (because the rafter is in the way) and then one that WOULD be full length (because it would be to the left of rafter #2)?
Hope I described it well enough for you to picture it and understand my dilemma. Chandler, you indicated I should sister them, now that I'm getting into the details, I ran into the problem of how to actually do it without shrinking my rough opening beyond the skylight specs of 44 1/4" wide. Let me know if you need clarification or more pictures. Thanks!
Imageshack - img5813s.jpg
Counting the rafters/joists from left to right, number them #1, #2, #3, #4, #5.
I'm going to cut #3 & #4 (both rafters/joists) to install a 44 1/4" wide (rough opening) skylight. I need to double-up joists & rafters #2 and #5
My questions are:
1. Can I double-up rafter #2 by adding a new one to the RIGHT of it? As you can see, it would not be able to be a "full length" rafter like the existing #2 is because joist #2 is "in the way"....so the rafter would have to "rest" on joist #2, is that ok? Or do I NEED to double-up to the left of the existing rafter with a full-length 2x6?
2. I need to double-up joist #2 to the LEFT of it, otherwise my rough opening for the skylight will be compromised. How can I double-up joist #2 to its left? Can I add 2 2x6's, one that won't be full length (because the rafter is in the way) and then one that WOULD be full length (because it would be to the left of rafter #2)?
Hope I described it well enough for you to picture it and understand my dilemma. Chandler, you indicated I should sister them, now that I'm getting into the details, I ran into the problem of how to actually do it without shrinking my rough opening beyond the skylight specs of 44 1/4" wide. Let me know if you need clarification or more pictures. Thanks!
#2
10-06-10, 10:39 AM
Nevermind. Got the answer I was looking for. I don't need to double-up anything if the distance between rafters/joists is less than 48". However, if I want "overkill", I can sister them and just use as close to full-length rafters/joists as I can get in there. That's what I'll be doing and I'll be able to meet the rough opening required by the skylight.
#4
10-06-10, 12:20 PM
2009 R802.9 Framing of openings. Openings in roof and ceiling framing shall be framed with header and trimmer joists. When the header joist span does not exceed 4 feet (1219 mm), the header joist may be a single member the same size as the ceiling joist or rafter. Single trimmer joists may be used to carry a single header joist that is located within 3 feet (914 mm) of the trimmer joist bearing. When the header joist span exceeds 4 feet (1219 mm), the trimmer joists and the header joist shall be doubled and of sufficient cross section to support the ceiling joists or rafter framing into the header. Approved hangers shall be used for the header joist to trimmer joist connections when the header joist span exceeds 6 feet (1829 mm). Tail joists over 12 feet (3658 mm) long shall be supported at the header by framing anchors or on ledger strips not less than 2 inches by 2 inches (51 mm by 51 mm).
Gary
Gary
