My house is 32X36. I am questioning the structural integrety of a 12-12 pitch roof with 24' rafters hung from a ridge beam VS. what I'd call a semi-truss. This will be a loft without pony walls and a cross beam will attach horizontally to opposing rafters 6' from the peek leaving a 10' ceiling. Because I'd rather not hang rafters from that height and wrestle with a heavy beam I am wondering if that configuration would be advisable. I like the idea of building each rafter set in a jig and they will be well secured at the bottom. Also there are 2 girders running crossway (32') in the floor plus the subfollring to hold the walls in. My concern is wether or not this design would want to push out the walls or if it is attached securely to the floor, does that create a large truss effect? Thank you for your replies. Dan

 

Greetings,

I can't answer your stress/load ?, but, I would like to caution you about how you insulate a rafter that is connected to the drywall and roof sheathing.

If you don't isoate and insulate the interior rafter surface from the drywall, it will conduct heat energy so fast that you will have heating problems summer and winter.

Radiant barriers work best for these systems.

If you want more info, let me know.

 

Thank you for that info. I'll remember that when I get to that point. I'm a ways from hanging sheet rock at this time. I'm building out of pocket so that will be next year's work. BTW, it will be a metal roof over 2X4 perlins. I assume your insulation caution applies the same as with conventional roof systems.

DaninAlaska

 

Greetings,

Is this commercial or residential?

I will have to check to see if there any precautions for you area.

I know the navy used RBs in the Artic, and still do. I don't recall hearing any problems up there.

The reason I bring this up is that normally you do not have condensation problems with RBs except some steel roof apps if precautions are not taken.

Thank you for your intrest.

 

This is residential - my own home. I am rural with no code requirements, however heat loss is obviously a consideration in Alaska.

While we are messaging, let me ask if you can refer another construction forum site. My main concern remains the framing design of the roof. I am finalizing the materials order this week and have not yet received any feedback on this question from this site.

I understand the rafters will tend to push out on the walls without the ridge beam configuration. To counter that I am doing several things. I'm using OSB on one 13' long interior wall that butts up to the west wall of the house about midway to create added rigidity. An Artic entry is located on the exterior of the east wall giving 2 vertical support points, again in the center of the 36' long house wall. The girders connecting these 2 opposing walls will be connected to the wall studs instead of flush mounted with hangers for added strength. The 2 girders are spaced 14' apart. (8', 14' and 14') With the horizontal rafter gusset 6' below the peek that finishes 16' high, I am reasonably comfortable with this design, but will not proceed without experienced input. Another consideration is the load. A 12 x 12 pitch metal roof will shed snow quickly keeping the weight down.

Any feedback from those having experience in this area is greatly appreciated.

Thank you,

Dan