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Author Topic: Construction Question  (Read 73309 times)

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Offline dan-l-b

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Re: Construction Question
« Reply #40 on: September 14, 2005, 08:46:25 pm »
Hi Jeff long time no talk to.   :D

As far as laying things out we always try to draw it out on ou shed floor or blacktop drive using tapes and squares and stuff.  Usually get it close enough for "who its for" :D :D
I was down all winter with back problems.  5 MRI's couldn't give the docs enough evidence to justiy surgery.  I was in a tremendous amount of chronic pain and the docs were looking to see if I was working a disbility or WC angle.  It took a CT miligram before they could see the real damage and I was in surgery in 3 days.  That was April 1 st and thank God, I am back to work and all looks bright. 

Dan-l-b

Offline Don P

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Re: Construction Question
« Reply #41 on: September 14, 2005, 09:03:54 pm »
I have no intention...or hope...of returning this body in mint condition. If I knew now what I knew then  :).

Quote
We will be spanning the 16 foot direction.

I think I understand, crossbeams are collar ties...those are too high to be of much effect in resisting spreading forces when you have alot of snow on the roof.
I was thinking of double 2x8 purlins running parallell to the ridge about midway between the birdsmouth and ridge. supported in the gable ends under the rafters...beams running across the ceiling. These would help the double 2x8 ridge support the roof under heavy load (40 psf where you are I think?). If you wanted to cantilever a section over a small porch at the end extending those purlins, the doubled ridge, and cantilever beams off the walls would work up to about 4' out. Those beams should be very good stock. The rafters would then be doing light duty.


 
Main 12x16 building is brown. Double 2x8 ridge, cantilevers and purlins are red. 2x6 rafters are black. I figured each of the ridge boards at 1-3/4" thick. Plumb to plumb is 105-3/8". Is that anything close to what might work?

The right pic is the rafter layout showing what I mean by plumb to plumb. I stuck a square on it with square nuts at 6/12. In light gray is "stepping off" a foot of span at a step. Stepping works but is prone to cumulative error.

 The diagonal measure of the triangle formed by the square and the board is in this case 1.118'. That is also known as the the line length ratio...go ahead multiply 94.25 (the horizontal run) x 1.118 (line length ratio)= plumb to plumb measure.

Offline Jeff

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Re: Construction Question
« Reply #42 on: September 14, 2005, 09:11:34 pm »
Don, So, how are the purlans supported on the gable ends?  Are they installed under and after the rafters?
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Offline Jeff

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Re: Construction Question
« Reply #43 on: September 14, 2005, 09:18:34 pm »
Don, How low would collar ties have to be in order to be effective?  My  wall hight is not a full 8 foot, it is only 88 inches. I want to get as much ceiling hight as possible
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Offline Don P

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Re: Construction Question
« Reply #44 on: September 14, 2005, 09:25:16 pm »
The purlins could go after, I was thinking of bar clamping them up to a popped line across the undersides of the rafters, attach with a twisted hurricane strap, purlin to rafter, then clamp another 2x8 alongside covering the straps, then stitch the two 2x8s together. You could bevel/rip the tops to make it sit plumb and neat. Then go to the gable ends and put 2 studs under and 2 alongside and around the purlins, same with the ridge. Follow those load paths to the foundation.

Lower third of the triangle or below is usually considered good on collars, the lower the better.

Offline Jeff

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Re: Construction Question
« Reply #45 on: September 14, 2005, 09:29:11 pm »
Isthere a way to estmate the ceiling hight using my width and pitch? 


What is a hurricane strap?  What is popped line? (chalk line?)
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Offline Don P

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Re: Construction Question
« Reply #46 on: September 14, 2005, 09:40:48 pm »
Floor to UNDERSIDE of ridge is 132-1/4" (I put the ridge flush to the bottom of the plumb cut).  Thats a total rise of 51-1/2" above the wall top to TOP of ridge. (I assumed a 3-1/2" level seat cut on the bird,I also assumed 2x6 rafters at 5-1/2", ridge at 1-3/4x7-1/4" x 2 ply)

Hurricane tie...twisted metal simpson connector, about 4"x 1-1/2" twisted 90 degrees and punched full of holes...lets you hook things together at 90*. By code you need them at the birdsmouth to wall joint as well.

Popped line=chalk line...ever been smurfed when the line spills? :D

Offline Jeff

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Re: Construction Question
« Reply #47 on: September 14, 2005, 09:44:55 pm »
Our codes dont call for hurricane straps.  Don, since I have a sawmill, couldnt I cut those purlins out of something solid and pretty, and leave them exposed acrossed the ceiling since they will be under the rafters? I can still insulate and put a ceiling on leaving the purlins exposed?
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Offline Furby

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Re: Construction Question
« Reply #48 on: September 14, 2005, 09:48:34 pm »
Actually Jeff, mine did on the addition, don't know about a shed.
They not only help against wind but also against seperation due to snow load on rafter framed roofs.

Offline Jeff

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Re: Construction Question
« Reply #49 on: September 14, 2005, 09:49:38 pm »
Well, maybe they do, but I have seen a lot of garages and stuff go up around here and never seen them used. I'll find some
Just call me the midget doctor.
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Offline Don P

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Re: Construction Question
« Reply #50 on: September 14, 2005, 09:52:54 pm »
Sure the purlins could be solid. I did give you Fb1250 psi to meet what I think are youre codes ...that is some nice stock.
 Then I think I might put some blocking between some of the rafters and lag the purlins up to the blocking while you're jacking things up and posting under the ends...trying to keep the purlins snug to the ceiling when its not very loaded and drying  ???.

Offline Furby

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Re: Construction Question
« Reply #51 on: September 14, 2005, 09:53:37 pm »
Let me correct what I said, my inspector requested I use them so to speak. ::)
Code calls for straps OR 3 nails, two from one side and one from the other.
I never have cared for a toe nailed connection anyways, due to the mangled wood and poor holding strength.

Offline Jeff

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Re: Construction Question
« Reply #52 on: September 14, 2005, 09:56:17 pm »
One thing that we really should still consider. This is still only a shed that I plan on cleaning out perhaps and let people change into swim clothes or sleep in during the summer. I want it to be a pretty shed, but still, a shed. :)
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Offline Larry

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Re: Construction Question
« Reply #53 on: September 14, 2005, 09:56:46 pm »
My way...Simpson Strongtie on the inside and another one on the outside.

Probably not to code as I did not use a double top plate...got the trusses centered over the studs.

I like Simpson...hope we don't have a hurricane in Arkansas.


Larry

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Offline Tom

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Re: Construction Question
« Reply #54 on: September 14, 2005, 09:58:32 pm »
Here is a PDF that sure comes in handy and is fun to read too.

http://www.awc.org/pdf/WCD1-150.pdf
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Offline Don P

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Re: Construction Question
« Reply #55 on: September 14, 2005, 09:59:49 pm »
I hear you, I'm giving the "hard" line. The safety factor on most wood is at least 2.1 times stronger than I gave you. The snow loads are listed higher than usually occur. I was just giving you what I feel comfortable writing in public, now its up to you  :).

That looks fine Larry, I did find out one way I did some "doubling up"was actually weaker than a single connector. I sometimes pays to double check before adding extra connectors in the same area.

Offline Jeff

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Re: Construction Question
« Reply #56 on: September 14, 2005, 10:01:10 pm »
Well, you'll wanta hear this then  :D   That catelevered overhang? I'm planning on it being closed in and a sleeping bunk. ;D
Just call me the midget doctor.
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Offline Furby

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Re: Construction Question
« Reply #57 on: September 14, 2005, 10:02:05 pm »
Larry,
Those are what I used, he didn't say anything about more then one each end of the truss, and passed what I used.

Yes Jeff, but you need to be protected from yourself, that's why they make all these rules. You have admited to possible planned uses as other then a shed, so it should be built to code!  ;) ;)
 :D :D :D

Offline Don P

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Re: Construction Question
« Reply #58 on: September 14, 2005, 10:12:46 pm »
Drop the ridge down to 131-3/8" to the underside...now the top edges plane and it hangs down inside about 7/8"...plumb cut on rafters is about 6-3/16"

My standard disclaimer YOYO, you're on your own  ;D.

Offline Don P

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Re: Construction Question
« Reply #59 on: September 14, 2005, 10:35:46 pm »
Oh in the flurry I forgot the formula you asked about originally.

Hypotneuse= horizontal span x (1/ cos (pitch angle))
Plumb to plumb= 94.25 x (1/ cos 26.6 degrees)
                         =94.25 x (1/ .8945)
                         =94.25 x 1.118 (remember the line length ratio I gave you earlier)
                         =105-3/8"

Your doin trig now  :D