# Does a hip roof need ceiling joists?



## Yoyizit (Jul 11, 2008)

All of these trusses
http://www.ufpi.com/product/rooftrusses/types.htm
are made from triangles because its shape won't change unless you change the length of a side.

In your case, no joist, no triangle?

If your joists are in tension the number and size of the nails at each end will give some idea of how much pull these things are seeing.


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## jpearson311 (Dec 29, 2009)

Yoyizit said:


> All of these trusses
> http://www.ufpi.com/product/rooftrusses/types.htm
> are made from triangles because its shape won't change unless you change the length of a side.
> 
> In your case, no joist, no triangle?


Hm, well, mine doesn't have any trusses. Currently there are the walls (2x4s with 22.5" span) and then rafters that sit on top of the top plate. I repeat, there are no trusses. The garage is 20'x20' and there are only 4-2x8x20's nailed to the sides of the wall studs, like the photo attached.


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## Willie T (Jan 29, 2009)

Just a guess, but since this is a garage, I would suspect that these 'ceiling joists' were held low like that to give room for storage above them. Shouldn't hurt to raise them. But 20' is a heck of a long way to span with only 2x8's if you are going to store anything up there.

But do NOT consider eliminating them. They are ties between the two walls, and need to be there to keep the rafters from shoving the walls outward. Move them one at a time, not all at once.

In my garage, no ties were put in place. The roof ridge began to sink over the years. I jacked up the ridge in a couple of places, and installed steel cables across where your rafter ties are... except that they were installed through small holes drilled in the rafters, themselves. The cables have turnbuckles, and I just tightened them up till there was no weight on the jacks. Then I removed the jacks. That was 25 years ago, and all is still well. (BTW... I could use only cables because we have no snow loads down here... so 'tension' only, was needed. Up North, you need both tension and compression. Thus, you use lumber, not cables.)

This gives you an idea of just how much work those ties are doing for you right now.


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## jpearson311 (Dec 29, 2009)

Willie T said:


> Just a guess, but since this is a garage, I would suspect that the ceiling joist were held low like that to give room for storage above them. Shouldn't hurt to raise them. But 20' is a heck of a long way to span with only 2x8's if you are going to store anything up there.


Yes that is exactly what they are there for. At least that's what I'm assuming. I just pulled down a bunch of old stuff from up above there. So, with that being said, do I even need the joists there as they are?

Jesse


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## Willie T (Jan 29, 2009)

jpearson311 said:


> Yes that is exactly what they are there for. At least that's what I'm assuming. I just pulled down a bunch of old stuff from up above there. So, with that being said, do I even need the joists there as they are?
> 
> Jesse


Yes, yes, yes! YOU NEED THEM. Do NOT eliminate them. They serve a very serious structural purpose. (See my other post)

*THIS* may give you some better understanding of the importance of rafter ties, collar ties and trussed rafters. Pay careful attention to the use of the words RIDGE *BEAM* in this article, as opposed to RIDGE *BOARD*. VERY important that you understand the difference.


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## jpearson311 (Dec 29, 2009)

Willie T said:


> Yes, yes, yes! YOU NEED THEM. Do NOT eliminate them. They serve a very serious structural purpose. (See my other post)


Ok that's what I thought. What other post of yours are you referring to?


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## Willie T (Jan 29, 2009)

jpearson311 said:


> Ok that's what I thought. What other post of yours are you referring to?


#4 in this thread.

Some things have been added to my posts since I first wrote them. Re-read them to be sure you miss nothing. This is important stuff. Roofs CAN and DO fall in from being incorrectly altered.


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## Yoyizit (Jul 11, 2008)

jpearson311 said:


> like the photo attached.


From your simple diagram, I can't imagine forces or a combination of forces that would cause a structural difference if you raised that horizontal beam/joist from its present position. I wouldn't lower it, though.


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## Scuba_Dave (Jan 16, 2009)

Wasn't this completely covered in your last thread ?

http://www.diychatroom.com/f19/raising-overhead-joists-my-garage-good-idea-64528/


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## jpearson311 (Dec 29, 2009)

Scuba_Dave said:


> Wasn't this completely covered in your last thread ?
> 
> http://www.diychatroom.com/f19/raising-overhead-joists-my-garage-good-idea-64528/


Yes it was Scuba, but when I took the entire surface out above the joists, it looked like I may have not even needed them. I just wanted to double check. Thanks!

Jesse


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