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Raising rafter ties

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Runner

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Looking to finishing 2nd floor in older house. Current height of rafter ties are 7' 6". I would like to possibly raise the ties another 6-10". If I did this would the rafter ties still be effective? I have read that rafter ties should be in the lower 1/3 of the rafters? See attached diagram

Thanks

image.jpg
 

nealtw

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Welcome to the site.
Usually the ceiling joist are the rafter ties, there must be a formula for how low the floor is and where to put the ties and there might be some cheats, work work arounds may sound better.
What comes to mind is a knee wall with angle braces down to the ceiling joists at the outside wall.
Might be a question for an engineer.
80" is a ceiling height by code.
 

bud16415

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I think it could be done what are the rest of your plan up there? What do you have for floor joists size and span?

And welcome to the forum.
 

nealtw

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I think it could be done what are the rest of your plan up there? What do you have for floor joists size and span?

And welcome to the forum.
It looks like he is already over the limit, pushing a few more inches might just be to far.
 

bud16415

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It looks like he is already over the limit, pushing a few more inches might just be to far.
His pitch is 12/12 a plus and we don’t know where he lives or what the snow loads or wind loads he has a short span across the building so that’s also a plus also. Here is an article on the subject and a calculator. He will have to let us know how much snow load he gets and then plug in some numbers to get an idea.

http://mathscinotes.com/2010/11/the-mathematics-of-rafter-and-collar-ties/

http://www.timbertoolbox.com/Calcs/raisedtiethrust.htm
 

Snoonyb

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OP, could you pull the insulation from between 2 studs below the top plate that the rafters sit on and provide a photo looking straight down in that stud bay?
 

Snoonyb

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The reality is, that the collar ties are the only element holding the place together.
 

Snoonyb

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While I'm aware of the "intended function" of both, rafter ties are seldom, if ever, tied to the ridge, as these are.

What draws my attention, is that the ties are newer than the rafter ties.

So why?

Was there spreading caused by the "rafter ties" being incorrectly placed?
 

nealtw

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While I'm aware of the "intended function" of both, rafter ties are seldom, if ever, tied to the ridge, as these are.

What draws my attention, is that the ties are newer than the rafter ties.

So why?

Was there spreading caused by the "rafter ties" being incorrectly placed?
Every time I look at it I have more questions.
I.am not sure the ties look new but there is lumber up on top so the ties going up may have been put there to help support that. That would be defeating the purpose of the ties.
It looks like there is insulation stuffed into the stud bays where fire stopping should be if it is balloon style framing.
Then if the ceiling was just built as a ceiling how is it attached to the balloon frame and we see no venting for the attic.
 

bud16415

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You guys can read a lot into a picture. I was noticing how the field stones were lined up funny in the basement.

Really 7’6” isn’t a bad height for an attic. That’s a lot of work to pick up more head room. When the OP comes back and tells us how much weight he is planning to add up there the ties will be the least of the problems.
 

nealtw

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You guys can read a lot into a picture. I was noticing how the field stones were lined up funny in the basement.

Really 7’6” isn’t a bad height for an attic. That’s a lot of work to pick up more head room. When the OP comes back and tells us how much weight he is planning to add up there the ties will be the least of the problems.
Get stuck with a couple bad quotes and you learn to look for detail.
Might easier to lower the floor.:rofl::rofl:
 

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