How far can you go?
I have seen some cabins (can't find any pictures at the moment) that have the gable stretch far out and the rafter tails sweep back in towards the building.
Some have extreme overhangs.
(http://www.smcalaska.net/albums/Construction-Pics/South_gable_and_6_foot_overhang_complete.jpg)
I have my own out about a foot with outriggers.
How do you calculate how far you can build them out? Is there any guide or rule?
That roof is incorrect. It is also just an extended roof. The plates would be sized as overhanging beams, with or without a ridgebeam depending on tie configuration and design.
A prow roof has lookouts designed as overhanging beams to a built up rafter pair( or could be more) that act as the inboard beam.
A "prow roof" was exactly what I was looking for. Thank you for help with the terminology. [cool]
(http://www.casualcountryloghomes.com/Prow%20Roof.jpg)
I'm still a little confused as to how to frame something like that and how far I can go.
He looks to be out there on glulams above and below so it is their overhanging beam strength. Using lookouts it is often their strength although the inboard rafter and the wall below can be factors. A lookout supported overhang of any size should adhere to the 2/3 inboard, 1/3 overhanging rule. Houseful coming tonite but I'll try to dig up an old framing pic.
I found a bad pic ::). Think of the lookouts as a major rafter/purlin roof, the lookouts are beams overhanging a support, they are supported by a large built up rafter and a support wall.
This calc is the one I would use for the lookouts
http://www.timbertoolbox.com/Calcs/ohangunild.htm
The formulas titled "simple beam load increasing uniformly to one end" in awc's DA6 would be the one to use for the inboard built up rafters supporting the reactions from the lookouts, calculated above. Also from those calcs the reactions at the supporting wall need to be checked... especially if there are headers, this is where there is substantial load depending on the length of that overhang.
That is exactly what I was looking for. Thank you very much.
Next up...... saddleback roofs.
(http://www.dailytravelphotos.com/images/2010/100821_rantepao_sulawesi_indonesia_tana_toraja_tongkonan_traditional_boat_house_peaked_roof_travel_photography_MG_3501.jpg)
Just kidding. ;)