Understanding Knee-Wall Top of Plate Calculation

[jayn1321]

I am having some issues with the auto story pole dimensioning in Chief. I have a second floor where the exterior wall will be a 36" knee-wall. From my calculations, we would have what is shown in the snip below. 9'-1 1/8" rough first floor, 11-7/8" joists+3/4" sheathing (1'-0 5/8") and then 36" to the top of plate. This totals 157 3/4" and is what I set the Top of Plate value to in the Roof Plate Specification by manipulating the Baseline Height. But you will notice that the auto story pole dimensions set it 15/16" above 36". Also, the section shows the top of plate below where it should be (see the manual dimension I added). I am wondering if I have some setting wrong or went about the setup the wrong way.

 

Thanks in advance!

 

[javatom]

Your roof plane is supposed to be rafters.  You might have the specifications set for trusses (no birds mouth).  There may be other things going on as well.

[GeneDavis]

How'd you build the roof way up there?

[jayn1321]

Rafter or truss, the story pole still does not define correctly at the 157 3/4". 

 

I manually placed the roof plane at the front wall, baseline on the outer edge of framing, then adjusted the baseline height to be a knee-wall.

[GeneDavis]

You can benefit this discussion by completing your sig lines in your account profile, so we know whether you are working in Chief X or Y or whatever, and maybe what you run the software on.

 

And then having done that, you can save and close the file and post it here.  If it is too big to post, strip the goodies out of it, leaving just walls and roofs, and it should post just fine.  Compress it if you need to.

 

Here is what I get when I build a two story house, second floor with 36" ceiling height, and then roof it.

[jayn1321]

Thanks Gene! It seems a bit counterintuitive to have the ceiling height be 36", but that did work.

 

I had the ceiling height at 109 1/8" and manually adjusted the baseline height, so something with that was causing it to be off. 

[rgardner]

2 hours ago, jayn1321 said:

Thanks Gene! It seems a bit counterintuitive to have the ceiling height be 36", but that did work.

 

I had the ceiling height at 109 1/8" and manually adjusted the baseline height, so something with that was causing it to be off. 

Search baseline heights in the forum and help file.  It is not where you think it is.

[jayn1321]

I understand baseline heights and their adjustments with the top of plate with or without a birdsmouth cut. Even if you adjust the baseline height to make the top of plate value equate to the exact elevation that it is supposed to be, it does not work. But that is probably because the Auto Story Pole dimensions pull the room specifications rather than the roof. 

 

Curious about the ceiling height change (36") versus maintaining the proper ceiling height (109.125"), I made a new plan with two equal structures. The one I made 36" ceilings with flat ceiling unchecked, and the other I made 109.125" ceilings with flat ceiling checked. I drew both roof planes manually. The 36" ceiling roof plane sat right at 157.75" correctly. The 109.125" roof plane obviously snapped to the 109.125" plate height and I adjusted it down by locking the pitch and adjusting the Baseline Height accordingly. 

 

In the end, both ended up being on the money with the Auto Story Pole dimensions with 36" knee walls. It looks like something in my original file was throwing it off, but I am not sure what. I'll figure it out or redraw it.

 

Thanks for the help everyone.