Sawn Lumber Ridge Beam Span

[Walnut]

I was wondering what the maximum span is for a 6x10 Ridge Beam that is sawn from Douglas Fir at at least a #2 beautiful almost flawless beam, don't see any knots.
Was wondering what the max span is and also if it can span 15' from post to post freely. It's supported by a 6x6 Doug fir beams on each end that are built into the wall and it solid all the way from floor to ridge beam. It will be supporting 2x6 rafters that are actually 2x6 not standard 16oc, 5/8" ply, then I've and snow shield them roofing steal. It will also be supporting solar panels and possibly a solar water system. We do get a snowload from time to time, some years none, some a little and every once in a while many feet.
I can't find any span tables for 6x10's online and would like to know if the 15' span is doable and if not could t be with knee bracing.

Thank You

[Don_P]

Your load information is absolutely undecipherable... throw me a bone man! 
Need the design snow load for your locale... building dept, codebook map, or tell us where you are. How much do the various panels weigh and where in the span are they located. Conservatively I'd pile them all in the middle of span and dump snow on them. Buildings can't run, you design for that worst snow or wind day... the one day in a century you'd just as soon see it survive. I'm not too awful far past a tender half century and I've seen my house go through greater than their maximum snow and wind loads, they are not overly conservative, or, it is tough to predict mother nature.

Then, I have a 15' ridge beam span. What is the building width? Is the ridge supporting one end of 10' rafters or one end of 50' rafters... see where I'm going? We need to know the area of roof supported not just the beam length.

Look under the end support posts, they shouldn't run just to the floor, the load path should trace down to a large footing under the support posts, we can figure out the post load and footing size when we have the load info.

If you can post good pictures of ends and all faces of the beam, by the description it might grade higher than #2... not sure if we can get anywhere grading online...that might be a push 

Anyway, if you can come up with that info we can probably come up with something. WSDD in the publications list at awc.org also has some large beam tables, it is a little tough to get through the first time but a good resource.

[Walnut]

Sorry, I don't know all theses things. Some years the snow is heavy some not at all. I haven't seen any in 3 years and they say around here some yeas it really comes down. I don't know I the snowload here, let's just assume for a lot 2500 feet in northern CA Shasta area.
All the posts are going down to the ground into footings that are 2 feet wide 4 feet deep, all the posts and loads go down to these footers. It's 24x16 the 6x10 is in 2 pieces to span the 24 with it over hanging the gable ends on each side by an foot. One of the 6x10's is 16' the other is 10' they meet on a center post that is not centered, but has footing below. Center post is 6x8 the end posts built into end walls are 6x6. The rafters on ridge beam that span the 16' gable roof are 15' in back from ridge beam to top plate on back wall with a 12" overhang. On the front they are approx 10' with a 12" overhang. I don't have the exact measurement in front to me. The rafters are actual 2x6's spaced 16 OC Doug fir. Then 5/8" ply then metal roof. Most houses around here don't look like they are built for heavy snow loads and are falling apart, so u don't assume it's a problem, but I want to build for that anyway. Let's assume for a wavy snowload and in that situation, can a 6x10 span 15' how far can it span in that situation? Will I need knee braces?

[Don_P]

I'm guessing 40 psf?
http://www.co.siskiyou.ca.us/content/building-division-design-information

Flat roof snow load below 5,000 feet elevations -  McCloud, Mt. Shasta, Dunsmuir, Weed and Happy Camp, 60 pounds per square foot.  All Other areas, 40 pounds per square foot.

No panel load info. Let's see where it goes with what we have.
Tributary width 8' X 15' beam span=120 square feet
Multiply by the design snow load 40lbs per square foot + the dead load 10 psf... 120sf x 50psf= 6000 lbs design load on the beam (no panels).

This is a beam calc of mine;
http://www.timbertoolbox.com/Calcs/beamcalc.htm
Inputs;
Load-6000
span-180
width-6
depth=10
Fb... #2=875, #1-1350
E...#2=1.3, #1=1.6
Fv-170

This is a roof, ignore the deflection pass/fail and read the calculated deflection and the allowable roof deflection, if you deflect less than allowed then you're good.

Knee braces do not decrease span, span is post to post... actually it is clear span between posts + half of required bearing length at each end.

You fail in #2 and are hard up against it in #1 if the loads are correct, without panels.

[Walnut]

Thank You, I don't really understand the FB and the rest below. So what you are saying is a 15' span won't work for me with the 6x10? What would be the max span allowable according to these specs? I used the calculator, but some things I don't fully understand.

[Don_P]

Fb, E and Fv are what are called design values. They relate to different strength properties of a material.
Fb, extreme fiberstress in bending. Bend a popsicle stick and watch how it breaks. The extreme bottommost fibers will begin to tear. So for any listed material and grade I can look up the allowable stress I can safely apply to that extreme fiber. The engineering calc is taking the load, span, width and depth and calculating the maximum stress on the bottom fiber and then comparing it to the published allowable stress for that species and grade. Allowable stress... this value has a factor of safety, wood is very variable. At the end of the day, no stick should break below the published value. The overwhelming majority should be twice as strong as that working limit. There can be sticks in the pack that are way stronger than the allowable working load (pick those out of a pack and use them in higher load areas).

E is modulus of elasticity. A rubber band is strong in bending but is too elastic to make a good beam. Each species and grade has a published value for how elastic the wood is. This number has no factor of safety, it is a "true" number. After the calculation it gives the amount of deflection, or sag, in the beam for the given span and load. We limit this because it is a serviceability issue, floors get too bouncy or roofs sag excessively. Most of the time deflection is what controls beam dimensions.

Fv, horizontal shear. This is usually a failure in a very short, extremely heavily loaded beam. The beam shears/splits along the grain and effectively becomes 2 or more thinner beams. This is another value with a safety factor of around 2:1. Residentially this is rarely what controls beam size.

So, if you noticed as the grade improved the strength and stiffness also improved. Fv is the same within a species regardless of grade.

Don't encroach on safety factors and grade honestly, they are covering your and other people's mistakes or simply stuff you can't see inside. Also always be aware of the end use of a beam, a rafter or joist is redundant. If one fails the house is in no danger. If the ridgebeam breaks, uh-oh.

I'll let you try, here's how
The trib width on the beam is 8' wide. 8' x 50psf=400 lbs per lineal foot of beam (no panels).
So take a stab at 12'
Multiply 12' of beam length X 400 pounds per foot load on the beam, enter 4800 lbs in the load tab and 144 in the span and try it, an iterative process, make another more educated guess and try again.
Holler if you get stuck.