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What size lumber do I need to support a roof over a mobile home?

What size lumber do I need to support a roof over a mobile home?


  #1  
Old 02-09-04, 09:40 PM
arcspark
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What size lumber do I need to support a roof over a mobile home?

I am planning to install a roof over an old 12 x 55 mobile home. I plan to stick build the rafters using #2 2x4 SYP on a 4:12 pitch set on 24" centers. I'll be using 1/2 sheeting, felt paper and asphalt shingles. I do not want to support this weight with the mobile home. I wish to install posts and a top band all the way around the structure to carry the weight. Due to length of structure and window locations, 6 posts down front and back side, each set 11' apart would work well. I plan to use 4x6 pressure treated pine for the post (large enough??) The top band will be doubled 2x lumber and will rest on top of the 4x6 post (secured with steel plates). I am not sure what dimension this lumber needs to be for 11' spans. 2x6, 2x8, 2x10 ??
 
  #2  
Old 02-10-04, 12:56 PM
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Use the 2"x8" and follow the rest of the plan as posted and you'll be fine. Good luck.
 
  #3  
Old 02-10-04, 05:20 PM
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If you get any amount of snow, you may want to increase the pitch of the roof, also shingles like more pitch. A blowing rain, has an easier path to leak, with less pitch and the use of shingles.

I would notch the inside top of your posts, so your plate beams(2-2x8's), will have more support.

Now, since your not planning on any joists to tie the opposing sides together, you better make the beams stout, or they will bow out from the weight of the rafters, and ridge beam, decking and roofing.

I would set your 4x6 poles so looking down the side of the trailer, your looking at the 6" sides of the poles. Notch the top in 3" and down 7" or the width of your beam. Once all your beams are set, and nailed into the notch all the way down one side, Fasten a long, straight 2x6 laid flat on top all the way down, Making sure you span over the butt ends of the beams going down the length of the trailer. This will give a stout, bow resistant plat to attach the rafters to.
 
  #4  
Old 02-11-04, 08:28 AM
arcspark
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I didn't make it to clear above, but I was planning to install 2x4 joist under each rafter to tie the beam front to back to prevent bowing out. But to do that, the top of the beams would have to be as high as the old roof peak. (The old roof was tin with about a foot rise to the peak). Stiffening with the 2x6 on top of the beam would allow me to lower the beams thus making the entire structure look better. I could still put some cross bracing from rafter to rafter to just clear the existing roof peak. I'll put some diagonal bracing on the underside of the rafters to stiffen the structure against wind movement end to end. Also I plan to fasten some diagonal bracing on the four corner posts (from post to beam) using 2x8s.
I'm the type that has to know the whole plan before I start. I can't just start and build as I go. I totally agree with the do it once do it right approach. Thanks guys for all your insights!
 
  #5  
Old 02-11-04, 10:26 AM
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Always best to do things right the first time. Good luck with the new roof & let us know how things go for you.
 
  #6  
Old 02-15-04, 07:00 PM
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Roof-overs are pretty common, premade trusses would be a good way to ensure strength.

I didn't catch exactly what you are visualizing, but it sounds like you want a pole barn without side walls. You might investigate what a local pole barn builder would charge for what you want.

Make certain that roof gets hurricane ties, or it might not be there for long. You may expend more effort keeping it on than on preventing it from sinking.
 
 

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