How to vault a ceiling (or "it landed on my head")

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  #1  
Old 08-20-04, 05:54 PM
BeanPole
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How to vault a ceiling (or "it landed on my head")

We have a post-and-beam house built in '68 which has a fairly shallow pitched roof (run 3 rise 1) constructed of 4x8 rafter beams set approximately 70" oc. (no ridge beam.. they just butt up against each other at the peak). the roof is "sheathed" in 2 x 6 tongue-and-groove boards running perpendicular to the rafter beams with a metal roof above that. There are horizontal 2x6's running from one wall plate-rafter intersection to the other (collar ties?) at ceiling height which is an abysmall 7'4". Besides the 8 collar ties under the eight sets of rafter beams there are more 2x6's (ceiling joists?) at about 18" oc filling in the gaps. These joists and the collar ties run the entire span (23') with no support from below.
The ceiling is currently paneled and the goal is to remove the panelling, put in new collar ties immediately above the existing ties and remove the old collar ties (raise the collar I think it's called) and hopefully remove the "extra" joists as well.
The span is 23'2" total (11'7" per rafter beam) and we want to use 4x8 or 4x6 beams for the new collar (douglas fir or red cedar) and leave the whole thing open when we're done.
It seems reasonble but I look at this and can't figure out what's holding the peak up besides the two roof beam leaning on each other and the skimpy 1x4 post which looks like it should split the 2x6 if there where actually any weight on it... probably the inverse. the 2x6 is hanging from the rafter-beams? Does this look like it would work?

htp://www.the-davies.com/the-davies/images/RoofDrawing2.JPG

The drawing is of the current structure (side view of a single rafter-collar assembly and top view of the entire roof). the intermediate ceiling joists are not in the picture and the board-sizes for the collar-ties and center post should be 2x6 and 1x4 respectively.

Thanks for any thoughts.

Any thoughts would be appreciated.
 

Last edited by BeanPole; 08-21-04 at 12:39 PM.
  #2  
Old 08-21-04, 04:08 PM
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BeanPole,

Are you sure there is no beam and if so how?

Are there any metal hangers between the rafters?
 
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Old 08-21-04, 04:10 PM
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BeanPole,

One more question, is there possibly a "beam pocket" that is directly under the ridge at both ends of the room?

This could be 2x4's mulled together or partial 2x4's with a header for support.
 
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Old 08-21-04, 04:58 PM
BeanPole
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I'm sure there's no beam. I've pulled the panelling down in one room and can clearly see the rafters and the 2-by decking above that. There are no hangers on the Rafter-beams (I can see the nails where they are toed-in to each other). I don't think there is a beam-pocket though I must admit I'm not certain what that is. At one end of the house there are large windows and above that an attic vent dead-center under the peak where any post would be. At the other end there is definately no post and no beam.

I'm working on a better (more accurate) drawing.
 
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Old 08-21-04, 05:38 PM
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BeanPole,

OK, then I am assuming that they may have done a reverse birds mouth on the rafters or if not, toe nailed in the rafters at the exterior walls. I'm surprised to hear what you found. Seems like a very poor way to construct a vault.

I personally would install a ridge beam and use hangers on that and install hurricane clips at the exterior wall.

You can still do what you are describing for collar ties to make it look great or even make false beams for the collar ties.

What do you think?
 
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Old 08-21-04, 06:00 PM
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BeanPole,

I'm sorry BeanPole. I am assuming one thing but after looking at your drawing, it appears that the you have built-on-site trusses. Correct?

In reading your desire to make this into a vault, I would place beams from side wall to side wall with either a vertical support or a diagonal strut to the roof on each side. I'd have to draw this for you to better describe my idea.

If you can do a better sketch, that would be great but I think I know what you need. I'll do a drawing.
 
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Old 08-21-04, 08:37 PM
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Beanpole,

If you want to take a look at this link, find the 3 - 3D views I made. I am assuming that the existing is what you have now and I did 2 of a proposed method.

I stress that you should consult a structural engineer for this as well as get a Building Permit as this is considered major structural change.

I have placed 2 - 2x8's on each side of the 4x8's. I think the best way and this would be confirmed by an engineer to use steel strapping from beam to exterior wall (each side). Then strapping at the peak from beam to beam. It may be suggested to install struts on each side of the ridge from beam to the double 2x8's to provide more support even though this was not done to begin with.

http://pictureposter.allbrand.nu/pic...E+ALTERNATIVE/

Hope this helps!
 
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Old 08-22-04, 09:02 AM
BeanPole
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Doug,
Those are terrific. Thanks so much. I will indeed be contacting an engineer prior to making any changes (the mortgage company would have a cow otheriwse) but I've been having difficulty communicating what it is we're trying to do (just picking up the nomenclature so I don't call the missing ridge-beam "the-horizontal board thingy in the peak." )
Your drawings will be immensly useful in that regard and the revised -drawings are dead-on what I'm hoping for.

Thanks again,
Peter
 
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Old 08-22-04, 09:10 AM
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Peter,

You're very welcome!

Glad I did something right.

Good Luck, have a great day and keep us informed!
 
 

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