new to forum introduction

[djgaloot]

Greetings,
My name is Dave Jeske
I have read many posts on the forum but have not been active on it. It looks to be a great community and resource.
I bought some wooded property and am starting construction on a small home/cabin (28x32).  The design is a hybrid,  energy efficient stick frame with a timber frame roof, 2x6 decking and poly-iso insulation. I was going to have a timber framing company do the roof as it was a fairly complicated cross gable roof. due to their long backlog, I am now considering doing the roof myself with a simplified design. I also acquired a sawmill so I can mill my lumber for my loft and porch timbers.
I will post a picture but I have a couple basic questions first so I can refine my design. 
I have been using the beam calculator for some preliminary sizing. 
1) Does the "total load" mean Live+Dead? and the next input line is just the dead load?
I am using 20 psf for the live load and 20 psf for the dead load.
2) On my design the ridge beam will be supported on the two ends and the middle. How do I determine if I need collar ties and if so, how big? with the ends of the rafters supported by the ridge beamone one end and the stick built walls on the other, there is no horizonal component of force. Or am I looking at it wrong?

I look forward to being a part of the forum and sharing my design and journey.
Dave

[Don P]

Hey Dave,

1) Yes, Total load is LL+DL and DL is just dead load. What I was doing there is... the deflection calc correctly per code. They don't care about dead load deflection (the built in deflection) only live load in the deflection check for maximum floor or roof deflection under maximum design load. The "active" deflection is what pops drywall and tile. The hazard tool at the top of the TF forum page has good snow load numbers. I suspect you are heavy on your DL and light on your LL, double check and dial those in, the deflection check very often determines beam size rather than strength.

2)If the ridge is a structural beam(s) capable of supporting its' portion of the roof (we need to talk about where the load is on a valleyed frame), Then there is no horizontal thrust, the roof is hanging from the ridge. If the ridge cannot drop the rafter feet don't push outward, only straight down.

"Collar ties". You used the term but were actually asking a question about "rafter ties", uhh yeah, blame the building code folks  :D. So you do not need rafter ties to control thrust if you have a structural ridgebeam roof. Then the code goes on to say, in reference to stick frame construction, you do need collar ties in the upper third of the roof OR metal straps over the ridge and attached to the rafters on each side of the ridge. Look to intent. If the wind gets in, usually a blown out gable, in Andrew roofs unzipped at the ridge and 2 roof planes flew off. The metal strap works fine and is buried under the roof decking.

Now post a pic 

[djgaloot]

Thank you very much Don,
I will check what the local snow loads are. I was thinking about the loads incorrectly. I was thinking snow load was "dead" (not moving ) load but the way you described it makes sense.

The metal straps also make sense. Is there a standard for what size to use?  I'll check the code.

Pictures will be coming!

Dave

[djgaloot]

 




 
This was my original roof design that I will NOT be using because the timber framer I was working with ended up with too long of a lead time. Not shown are the four ridge beam posts or stick built walls. I believe the joinery is too difficult for me to accomplish by myself in a reasonible timeframe. Therefore, I am presently converting my design to a gable with two shed roofs which I feel I can pull off. I will post pictures of my proposed design soon.