The Forestry Forum

I'm milling nw cedar into a small post and beam (20X16) cabin and have some questions on rafters.  I'm cutting 4"X6" 's for the rafters, and I'll be putting 1" boards on top of that for the roof.  The pitch will be 6-12.  How many rafters should I use?  Can I get away with 4' on center?  Any thoughts?

I hate it when the computer eats a response.

If you'll have ceiling joists the calc I posted this morning should do it
enter your snow load
10 psf dead load
oc spacing
96" span
6 for 6/12
your rafter dimensions
Fb- 500
E .7
Fv 120
lateral nail in cedar is going to be about 59 going through a 2x ceiling joist into the rafter.

I see that your in northern Michigan too. My biggest concern was the snow load and the snow belt areas. I built my cabin last year in the eastern UP south of Paradise and I cant get back there in the winter without a sled. So I up'ed the pitch to 10/12 and put metel on the roof then I know I dont have to worry. I still ended up goin 2 foot on center for mine. I know I went overboard but I dont want snow bringing down the roof. One thing about the cedar over the rafters is that there is no need to finish the interior ceiling. Great idea!!!! looks great too. Did you put the cabin on a platform off the ground? Are you in need of any Oly screws, foam gasket for the logs? I have some left over stuff if you need it.  If you need help let me know.
Cary in Traverse City

Walleye offered up excellent advice and brought up what should be a major concern for Yuppers.....snow load.

A lot depends on your location in the UP.   If you're in the snow belt, a steeply pitched roof (at least 8/12) and a metal roof should be a given.  With snowfalls of 200" a season near places such as Houghton, better to be safe than sorry.
2' on center is the only way to go.  Always overbuild.  10 years from now when your place is still standing, you'll be glad you went the extra mile during contruction.

I've seen countless buildings crumble from snow loads here in Three Lakes Wisconsin.  We are located about 60 miles from the "snow belt", but heavy snow seasons still occur maybe once every 10 years. 

An acquaintance of mine went through this.  His pole building/workshop was poorly designed. The engineered trusses were 6 feet on center.  The 4/12 metal roof had 3 feet of snow on it.  Then it started raining in March.  The additional weight of the rain was too much. It made the pole building fold up like a cheap suit, destroying the building and its thousands of dollars in power tools/machinery/etc.  His homeowners insurance covered less than 1/2 the cost of the losses.

Thanks for the advice.  I'm building on Stonington peninsula, so I'm not in the major snow belt...still I should account for heavy snow loads.  I lived in Grand Marais and we got 350" of snow in one year. 

The cabin will just have a green treated foundation blocked up off the ground.  I looked around for simple designes, and came up with a nice looking post and beam with a porch that will go together easily with my M7 mill.  It will be a nice hunting cabin for us.  BTW Walleye, I'm in Elk Rapids.