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don't over engineer it.
For me? With same problem as you? I use 2x3's, cut them down to actual 2" depth, and used 3.25" framing gun to attach end-on. Yep.
I was faced with the same problem with 2x6's in attic and needed to get the "Raft-R-Mates" in and also some modicum of insulation. Raft-R-Mates (pink styrofoam channels from owens-corning at home depot .99 each) are about 2" deep. r-19 insulation was listed at like 6.0" deep. (sure, I wanted r-25 insulation or whatever, but that gets like 8" deep by itself) So total 8" deep with r-19 and raftermates. But rafters were 5.5 deep. So, I needed 2.5 inches. Well, I thought of "daughtering" (side-by-side, with overlap) a 2x4 and putting in nails laterally through the studs and rafters, but this was a heavy load and also would then "skew" the channels. Further, studs get expensive at that quantity and heavy. So, I used 2x3"s and cut the depth to an actual 2" deep. And I attached them end-on, like a complete extension of the 2x6 to 2x8. Which is why I bought my first bt3100. Ripped like 100 of these that way.
Why 2", especially when I needed 2.5"? Well, I got to thinking that attaching these things would be a bit of a thing. Screws? Brackets? Nails are fast an easy, but with a 2.5" additional framing member, framing nails at 3.25" long would only give me .75 of cleat. Whereas 2" deep would give me a full 1.25" cleat from the nails. Now, putting these nails straight in (perindicular) might allow them to work themselves out over time. So I put them in at odd angles, like 45 degrees to the rafters, alternating over 12" spacing at 45 degrees one way and then the other way (to form a "v" shape or a "y" shape), so that they couldn't work themselves out relative to one another.
Now, why'd I do this. Well, I figured I could compress the insualtion a bit, and compressng insulation a 1/2" was acceptable. Plus, if I built the rafters out too much, I would lose much needed head room in an attic. Next, I got to thinking that this was not going to be under a heavy stress (weight). The rafters already carried the weight of the roof and roofing materials. I was going to merely hang drywall once insulated and drywall is not that heavy (relatively speaking).
So, I took my unfinishe attic, ripped 2x3" to 2x2, attached them butt end on, anchored with 3.25" framing nails, staggering in angle and spacing, and then used rafte-r-mates with r-19 insulation. Drywall over that, screwing into my 2x2's and all is well. 2 years later and no cracks or sagging or whatever. And, the attic is quite warm in the winter and despite only r-19 insulation, appears to keep snow onthe roof as well as other neighbors with r-25 insualtion. Of course, I also insualted the floor to help, with a heavy carpet pad and carpet.
I dunno, just how I did it. You can do it any number of ways, but just don't over engineer it. Its rafters. they're not load bearing in the sense you're gonna walk on them. the rafters, as is, already carry the weight of the roof, so you don't need to add extra rigidity. Of course, you also don't want to add too much weight either.
well, good luck.
curt j.
For me? With same problem as you? I use 2x3's, cut them down to actual 2" depth, and used 3.25" framing gun to attach end-on. Yep.
I was faced with the same problem with 2x6's in attic and needed to get the "Raft-R-Mates" in and also some modicum of insulation. Raft-R-Mates (pink styrofoam channels from owens-corning at home depot .99 each) are about 2" deep. r-19 insulation was listed at like 6.0" deep. (sure, I wanted r-25 insulation or whatever, but that gets like 8" deep by itself) So total 8" deep with r-19 and raftermates. But rafters were 5.5 deep. So, I needed 2.5 inches. Well, I thought of "daughtering" (side-by-side, with overlap) a 2x4 and putting in nails laterally through the studs and rafters, but this was a heavy load and also would then "skew" the channels. Further, studs get expensive at that quantity and heavy. So, I used 2x3"s and cut the depth to an actual 2" deep. And I attached them end-on, like a complete extension of the 2x6 to 2x8. Which is why I bought my first bt3100. Ripped like 100 of these that way.
Why 2", especially when I needed 2.5"? Well, I got to thinking that attaching these things would be a bit of a thing. Screws? Brackets? Nails are fast an easy, but with a 2.5" additional framing member, framing nails at 3.25" long would only give me .75 of cleat. Whereas 2" deep would give me a full 1.25" cleat from the nails. Now, putting these nails straight in (perindicular) might allow them to work themselves out over time. So I put them in at odd angles, like 45 degrees to the rafters, alternating over 12" spacing at 45 degrees one way and then the other way (to form a "v" shape or a "y" shape), so that they couldn't work themselves out relative to one another.
Now, why'd I do this. Well, I figured I could compress the insualtion a bit, and compressng insulation a 1/2" was acceptable. Plus, if I built the rafters out too much, I would lose much needed head room in an attic. Next, I got to thinking that this was not going to be under a heavy stress (weight). The rafters already carried the weight of the roof and roofing materials. I was going to merely hang drywall once insulated and drywall is not that heavy (relatively speaking).
So, I took my unfinishe attic, ripped 2x3" to 2x2, attached them butt end on, anchored with 3.25" framing nails, staggering in angle and spacing, and then used rafte-r-mates with r-19 insulation. Drywall over that, screwing into my 2x2's and all is well. 2 years later and no cracks or sagging or whatever. And, the attic is quite warm in the winter and despite only r-19 insulation, appears to keep snow onthe roof as well as other neighbors with r-25 insualtion. Of course, I also insualted the floor to help, with a heavy carpet pad and carpet.
I dunno, just how I did it. You can do it any number of ways, but just don't over engineer it. Its rafters. they're not load bearing in the sense you're gonna walk on them. the rafters, as is, already carry the weight of the roof, so you don't need to add extra rigidity. Of course, you also don't want to add too much weight either.
well, good luck.
curt j.
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