Long span sorta cathedral ceiling

[blamm]

WARNING-I'm a slow 2 finger typist. My question- I live in central New England and i want to attach a 15x15 three season room (no heat) to my 2 story home. The boss wants cathedral looking ceiling with no supports in the interior of the room. The roof will drop less than 3 feet from one end to the other. She also likes the look of exposed beams. Question-If I use rough cut hemlock timbers, what size do they have to be? Many thanks for any reply.

[Don_P]

2 fingers!... show off :)

Is the roof a gable that extends out from the present house with two 7-1/2' foot run pitches to a ridgebeam or is it a shed roof simply sloping from a roof or wall, and which, attached to roof or wall?

What is your design snow load in lbs per square foot? Location?

Does the timber need to be graded?

[blamm]

roof is shed-attached to house wall and attaches to "new" wall 15 feet away' live in sw new hamp-snow load is 50 lbs I believe. timber is not graded hemlock'

[blamm]

oh yeah-and I'd like to do it with only 5 beams which would put them about 4 ft apart. would go 6 beams if prodded.

[Don_P]

NH has native timber laws, no grading needed. The rest of us would do well to read and push for the same.
50 lb live + 10 lb dead load (typical for the roof weight itself)= 60 psf
4' widex15' long= 60 sf
60psf x 60sf= 3600 lbs load/rafter
I'll let you work it yourself in case you want to make some adjustments to spacing or whatever in the above.
http://www.windyhilllogworks.com/Calcs/beamcalc.htm
Inputs are;
Load-3600 lbs
span- 180"
width-7
depth-9
Fb-862.5 psi (this is a #2 adjusted for snow load duration)
E-.9 (the pass/fail is set for floor stiffness here, notice a roof is allowed to sag more)
Fv-140

[blamm]

thank you so much Dan P. I think I have everything I need.