cjanderson66

Birdsmouth Cut To Match Existing On Framing

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Ok so I am doing an addition and have existing 2X6 rafters but will be using 2X8 rafters on the proposed.  We have all pretty much come across this situation where we need the roofs to plane in with each other.  In the attached drawing this is what happening to the ceiling  because the wall height is lowered to accommodate the new rafters depth.  How do I change the walls to match the existing height and the birdsmouths cut is deeper?  The wall needs to come up 2-5/16" to match the bottom of the ceiling joists.  Anybody have any answers....Chief?

Elevation Image.pdf

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Ok so I am doing an addition and have existing 2X6 rafters but will be using 2X8 rafters on the proposed.  We have all pretty much come across this situation where we need the roofs to plane in with each other.  In the attached drawing this is what happening to the ceiling  because the wall height is lowered to accommodate the new rafters depth.  How do I change the walls to match the existing height and the birdsmouths cut is deeper?  The wall needs to come up 2-5/16" to match the bottom of the ceiling joists.  Anybody have any answers....Chief?

I think you can open the roof plane and change the birds mouth depth and width.  Keep  in mind you will need two roof  planes,  one for the 2x6 and one for the 2x8

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Sometimes the new 2x8 will stick though the ceilings in a room camera view b/c the program won't cut the rafters at the ceiling line. If that happens just turn off the rafters in that camera view.

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Yes but Is there a way to raise the wall height to match the bottom of the ceiling joists so it shows correctly?  Thanks by the way.

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Hows that, I haven't found a way. The framing sticks down below the ceiling every time. raising the wall does nothing for me. 2 different rafter sizes like 2x6 and 2x10 just don't work from inside aliging the tops. all I'm saying is the rafters do not align at the ceiling height.

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I dont get the issue.   Raise the clg ht and make the rafter sit at whatever depth you want. (for proper birds mouth depth or whatever your desired stand height is.

 

If you are talking about the tail of your rafter getting skinny, that is just the framing DBX of that roof plane.   Change gable sub fascia to 7.25 and you will have a straight tail.

 

As for getting the ceilings to align, it should not be an issue as the 2x6 has to be elevated to flush out the roof plane.   

 

I am just not seeing the issue.

 

This is another case where this would probably take all of 30 seconds to answer if you posted the plan and gave desired clg hts...etc.   (just saying ;) )

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Seriously Justin maybe it is possible that you have been lifting way to many heavy things and don't understand the actual question as well not understanding the visual presentation of the PDF.  We are all talking about the eliminating the small vaulted portion of the ceiling as to have a longer seat cut to the rafter and nothing to do with the tail of the rafter.  Raising the ceiling height does not fix the issue of the the wall height nor eliminating the small vaulted portion.  (Just sayin   :ph34r: )

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I don't understand the problem either. Can't you just break the wall in an elevation view and simply make the appropriate section taller or shorter?

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You know...without seeing the plan we can only make assumptions here, but from what it looks like to me, your existing wall heights need to be left alone, and the height of your new walls needs to be shorter (as opposed to making the birds mouth deeper). If the birds mouth is deeper you lose most of the structural benefit of the bigger rafter. Like I said, you should be able to simply break that wall and drag it down in an elevation...OR, give that area a unique room definition with a lower ceiling.

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You don't necessarily lose the all of the structural integrity of the rafter if there is a ceiling joist nailed directly to the side (and strategically placed nails). However I agree it's not ideal. I have messed with this a bit and I can get it to sort of work by un-checking "Automatic Birdsmouth Cut" in the roof DBX and changing the seat cut but then it leaves the bottom of the rafters hitting below the ceiling on the inside. This does fix the the angled ceiling problem on the inside though.

 

A work around could be turning off the rafters layer for camera views and a CAD mask in section views to cover up the the rafter. Or if it's a simple enough roof where all of the 2x8's are the same you could make a polyline solid of the rafter and copy them across the plan.

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Okay, I finally understand what you're talking about. You're talking about getting rid of the little sloped section of ceiling...

 

post-46-0-92336500-1449038337_thumb.png

 

Sorry, don't know the answer

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I do not think there is a better solution other that what Perry suggested which is to live with it but turn off rafters for 3d views.

 

I played with predefining the birds mouth...  a no go.....  I tried using a thicker wall to get the auto birds mouth,  lock roof framing,  change thicker wall to thinner wall...  another no go....  I have no solution,  I played with this a long time ago and I could not reach a solution.

 

 

Glenn,  where fore art thou?

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Scott, you did a great video on this a while back, it's a bug for sure and needs to be fixed.

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Seriously Justin maybe it is possible that you have been lifting way to many heavy things and don't understand the actual question as well not understanding the visual presentation of the PDF.  We are all talking about the eliminating the small vaulted portion of the ceiling as to have a longer seat cut to the rafter and nothing to do with the tail of the rafter.  Raising the ceiling height does not fix the issue of the the wall height nor eliminating the small vaulted portion.  (Just sayin   :ph34r: )

 

 

Na....just not the way I draw (or would build) so it was difficult to see what you mean.    

 

The weird thing I thought would work would be to delete ceiling and draw on in manually and even though the clip lines on the floor plan went away, the roof still followed vault??? That had me puzzled.   

 

Frankly, I would draw it with 2x6 and the do "cad detail from view" for my sections.   That is what I do anyway.   Then I would edit rafter depth and manually draw the deeper cut on rafter.

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Maybe I am not following this correct, but in the original post it was said that he had the roof planes coming together correctly but wanted the birds mouth to be the same to make the ceilings match. In my world this will not be possible . You cannot use rafters of 2"x8"s and tie into a roof with 2"x6"s and have the roof plane and the ceiling plane both match. The only option to get the matching birds mouth is to lower the wall to make up for the vertical difference between the two different rafters which will still leave you with an offset in the ceiling. Just another one of those things where you have to make a decision as to what is the most acceptable results.

 Have a great evening to all,Ken

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...... You cannot use rafters of 2"x8"s and tie into a roof with 2"x6"s and have the roof plane and the ceiling plane both match......

 

Incorrect...... it is possible......  the ceiling plane is flat ....  you are not following the issue.....

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Yes , it is possible. The problem is that Chief doesn't cut the rafter off at the ceiling line like it should.

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Yes , it is possible. The problem is that Chief doesn't cut the rafter off at the ceiling line like it should.

 

I believe that Perry is correct.

Chief will only make the birdsmouth cut the width of the wall.

It will not extend the cut into the room past the inside of the wall.

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