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Looking for input on 32x44 post and beam

Started by Tyler.schmick, May 02, 2017, 05:38:14 PM

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Tyler.schmick

Hello, I am new to the forum and new to timber framing etc.
I have been planning my post and beam (I plan to make the connections with metal plates)...
I was looking for input or critiques! The brown posts are 8x8, the white are 6x8 and the purlins are 4x4.
House is 32x44.. sitting on an icf foundation.




addicted

Nice frame
I like your stairs
You may want to run your chimney a little higher though :D
What brand Icf are you going to use? Have you used icf's before?

Tyler.schmick

Ha! Yes... definitely need to run the chimney a bit higher... icf is already up! I used nudura and they are awesome!


Ljohnsaw

Interesting.  So the bent spacing is just under 9 foot?  Did you do load calculations (including snow) on your purlin sizing?  Aesthetically, I think 4x6 would look better on them (exposed, right?) and probably would be required for that span.  Next to the 8x8s and 6x8s, the 4x4s are going to look like toothpicks!
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

Tyler.schmick

Yes.. bent spacing just over 8 ft.. I plan on sitting the bents to the inside of the icf so I can 2x4 and insulate around the outside(and leave as much exposed timber as possible. Thanks for the suggestion on 4x6 vs 4x4, that is great advice. I could use come help on load calculations!
Thanks for the reply!

Ljohnsaw

To do load calcs you need some information:

Snow load - county information for your area (if you get snow)
Roof composition - metal, asphalt shingle, wood shingle
Roof pitch
Structure (dead load) - beams, purlins, sheathing, etc.
Cold roof or warm roof - will this be a fully occupied or just a vacation place

Then you start the sizing calcs and circle back if you need to up size them (up the dead loads for the new sizes).  This should be able to be completed in a short time (less then an hour).
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

Tyler.schmick

Snow load 21lbs
Wind 90mph
Roof metal
Pitch 12/12
Warm roof

Structure (dead load) is what I don't know exactly.. I found an oak source in Missouri that I want to use but it is going to be heavy! I will try to find out more info on the wood today, any other specific needed for dead load calculation is appreciated!

ChugiakTinkerer

I'm just another guy on the internet, so value my advice in accordance with what you paid for it.  :D

To calculate dead load you just add up the weight of everything in your roof and divide by the area to get a number for calculation purposes.

Assume 65 lbs per cubic foot for your green oak.  An 8x8 rafter runs around 22 ft long so that one will weigh about 650 lbs.  A 4x4 purlin will run about 61 lbs.  If you have 12 purlins eave to ridge, that's 732 lbs.  Add them together and divide by the tributary area (bent spacing times rafter length) to get a sense of what the timber frame dead load will be.  I estimate it around 7.2 lbs per square foot.  Add in your roof metal, roof felt, insulation, ceiling material and all fastening hardware and you may be close to 15 lbs per square foot.

There is a rather complex method to calculate a design roof load based on the ground snow load and the factors that ljohnsaw outlined.  It starts out as 0.7 * GroundSnowLoad and then applies a bunch of scaling factors.  I've stepped through this calculation for my cabin design and it amounts to a roof design load that is about half of my ground snow load.  It wouldn't surprise me if the specific conditions of your build result in a similar reduction.

Calculating loads for sizing beams and purlins should be done with a minimum of 20 lbs live load, regardless of what the roof design load ends up being.
Woodland Mills HM130

ChugiakTinkerer

Disregard the following if you've already considered it.  Since you are in an area that gets snow, you'll want to look at ways of protecting your doors that are under the eaves.  Snow will slide off the roof and pile up at the drip line.  A gable porch roof over the door is one way to keep the walkway clear and the walkers safe from falling snow.  Moving doorways to the gable ends of the building is another.
Woodland Mills HM130

Tyler.schmick

Thanks for the input! That is actually really helpful!

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