Porch Ceiling Plane Conflicting with Roof Plane

[Chief45]

The ceiling plane on a vaulted porch ceiling is being broken up and I'm not sure why. I have reduced the size of the roof framing to to ensure there is no interference and it didn't change anything. What is causing this interference with the ceiling plane on the right side? 

 

The top photo is with the manual ceiling planes added, left side is fine, right side broken up for no apparent reason. 

 

The second photo is if I select "use soffit surface for ceiling" to show what is going on before I try to add the custom ceiling plane. Any help is appreciated!

 

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[robdyck]

You should post the plan. That being said, ceiling planes almost always need 'use room ceiling finish' unchecked to model correctly.

[Chief45]

Here's the porch file. I unselected "use room ceiling finish" and tried to reduce the porch ceiling height to see if it lowers below the interference and it doesn't change anything. 

copy Plan to Upload Porch issue.plan

[robdyck]

Keep in mind that a sloped ceiling that is generated by a roof plane can't extend beyond the actual roof plane. In this case, the ceiling couldn't possibly extend to front door wall because the roof plane doesn't. This leaves you with 2 options: 

1. use a ceiling plane (preferred) OR
2. extend the roof plane to the front door wall

[robdyck]

In your case, you've used a ceiling plane, however it is higher than the bottom of the rafters (structure tab) of the roof planes. Seeing as your ceiling planes are not symmetrically balanced with the roof planes above, you should do some cleanup. That being said, you have a couple of options to fix the model:

1. reduce the structure depth of the roof planes OR
2. lower the ceiling planes so they are below the roof structure

Because I don't know your structural preferences or requirements, I'll leave the 9 1/4" rafters as-is and lower the ceiling planes.

As you'll see, that leaves some decision making about how to deal with transition depth from rafters to eaves at the gable end.

[Chief45]

Makes perfect sense now. Thanks!

[robdyck]

I'd like to make suggestions:

1. Use Posts for the...posts.
2. Use a Beam for the Beam. A General Framing member works as well.
3. Use a 3d molding for the diagonal members of your truss.

These adjustments will give you improved control and appearance as the wood grain will run the correct direction on all components. You can actually use a truss to model that truss, but that is a bit more of an advanced method. And you can assign those items to whatever layer suits your needs.