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snmhanson 12-14-2006 03:37 PM

Adding a snow supporting arbor
I would like to build an arbor off of our covered patio that I can place some sort of panels such as thick plexiglass over during the rainy and sometimes snowy winter season to cover our outdoor kitchen and hot tub. I would like to suspend one side of the arbor below a couple of simple span beams that support the roof of a covered patio. The beams are DF Larch #1 4x10 and I can't find any loading charts for DF beams. In any case the patio roof from the edge of the eave to the edge of the opposite eave is 13' and the spans of the two beams that would support the arbor are 8' and 9' with the end of one beam being tied into the house and the rest supported by DF #1 4x4s. The roof is built out of trusses and the ceiling of the patio is 5/8" drywall. So, using a 65 psf total load and ignoring the effect of the hip (which would decrease the loading on the beam anyway) I get a 425 plf uniform load on the beam.

The arbor is going to extend 13.5' out from the patio beam with the span between the patio beam and the outer support beam being 12' and then 1.5' of overhang. The arbor will need to be designed with the snow load of 50 psf and I guess the weight of the materials would need to be included in the loading calcs as they will be significant, however, I am not sure what I will be using yet. I guess I could figure a DL on the arbor of 15 psf which would give me 65 psf total load. Ignoring any effect of the 18" overhang this translates to an additional ~390 plf on the patio beam almost doubling it's current load. And the load at each beam (spaced ~1'8" O.C.) would be 650 lbs. (It will also add to the design load of the footings by 1,755 and 3,315 lbs and to the connection to the house by 1,560 lbs so I technically should probably run the calcs on those as well.)

So, I guess with all that said, and assuming my calcs are correct, could anyone tell me if a 4x10 DF Larch #1 beam with a 9' span could support a 815 plf uniform snow load? If not can someone direct me to a place where I could get the loading info for Douglas Fir beams? And my other question I guess would be assuming the patio beam can support the hanging arbor beams as described above what type of connection mechanism should I use? I would like to use lags versus hangers for aesthetic purposes if they would be strong enough. Thank you very much for any help anyone can offer here. And if you need more info please let me know. I could even supply and AutoCad file if necessary. Thanks again.


mdlbldrmatt135 12-15-2006 05:05 AM

DF should fall under the SPF load charts.......

snmhanson 12-15-2006 06:21 PM

Thanks for the reply. I assume SPF stand for Spruce-Pine-Fir, correct? If so then I can find the SPF charts that show maximum spans for 2x lumber given specific live and dead loads but nothing for 4x or larger lumber. I also can not find anything that shows loading capabilites in plf or other information such as moment and shear capabilities for any lumber. And also, I can't find fastener info to determine capabilities of lag bolts which I hope to use to hang the 4x6s from the 4x10 beams. I am hoping someone can at least give me a link or source to get the info I need to figure this out. I would be very appreciative of that.


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