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Old 09-10-2019, 11:50 AM   #16
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Re: Garage Rafter Supports


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Originally Posted by huesmann View Post
Actually, the king post would be in compression.
(You're also assuming each member is zero dimension.)
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Originally Posted by huesmann View Post
Are you assuming the members are weightless, and that the only load on the roof is due to the roof covering?
Everything has weight, its called gravity. In structures, there are internal forces (how the load is transferred) that you cannot see with your eyes. Rather than getting in a back and forth on this thread, you can search the web for a little basic information. I did a quick one for you, here it is.
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Old 09-10-2019, 11:59 AM   #17
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Re: Garage Rafter Supports


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Originally Posted by 3onthetree View Post
Everything has weight, its called gravity. In structures, there are internal forces (how the load is transferred) that you cannot see with your eyes. Rather than getting in a back and forth on this thread, you can search the web for a little basic information. I did a quick one for you, here it is.truss
You have to agree that compression down the center to 20 ft 2x4 would have done nothing to hold the roof up. I think the question is, does the roof have a sag in the middle that should be corrected. If not, no loss.
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Old 09-10-2019, 12:15 PM   #18
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Re: Garage Rafter Supports


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You have to agree that compression down the center to 20 ft 2x4 would have done nothing to hold the roof up. I think the question is, does the roof have a sag in the middle that should be corrected. If not, no loss.
That's the thing, a king post does not hold the roof up, that's why you usually find only a couple and minimal size at that. Gable rafters don't need them - they push out the outer walls, which in turn "stretches" the ceiling rafters, which "bends" the ceiling rafters down. So a king post "pulls" up on them.

If the rafters, king posts, braces, and ceiling ties were all transferring the "weight" directly down, this roof would have collapsed immediately.
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Old 09-10-2019, 12:28 PM   #19
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Re: Garage Rafter Supports


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Originally Posted by 3onthetree View Post
That's the thing, a king post does not hold the roof up, that's why you usually find only a couple and minimal size at that. Gable rafters don't need them - they push out the outer walls, which in turn "stretches" the ceiling rafters, which "bends" the ceiling rafters down. So a king post "pulls" up on them.

If the rafters, king posts, braces, and ceiling ties were all transferring the "weight" directly down, this roof would have collapsed immediately.
when we do trusses for heavy snow loads the big concern is the 2x4 or 2x3 members bending side ways under load so we get a list of crap to add to trusses to keep those members straight. So 1xs were there just to hold the joists up and i think they can be removed. The new 2x10s will sag but they don't need that support or something could be added to the side like in a nee wall position.
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Old 09-11-2019, 07:01 AM   #20
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Re: Garage Rafter Supports


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Originally Posted by 3onthetree View Post
Everything has weight, its called gravity.
If everything has weight, then all non-vertical members will be in both tension and compression.

I see you are assuming the joists are not continuous, and instead have a joint in the middle, at your kingpost.
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Old 09-14-2019, 04:59 AM   #21
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Re: Garage Rafter Supports


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Originally Posted by huesmann View Post
If everything has weight, then all non-vertical members will be in both tension and compression.

I see you are assuming the joists are not continuous, and instead have a joint in the middle, at your kingpost.
A compression member is between other members. A tension members is nailed on the side of other members
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