adding a rafter layer

[chrisinnh]

Learning curve is so slow for me... ugh.

 

I'm design/ build and do quite a few whole house rebuilds where I add a non-bearing roof over the existing to increase insulation values.  I have one such project on the horizon, a saltbox will be converted to a clerestory, and non bearing roof built over the sections of the current that remain.  Chief will not let me add a rafter layer, like a double stud wall, for example.  The new rafter layer will comprise the overhangs, the existing overhangs will be cut flush with the wall framing.

 

Thoughts?

Edited Monday at 11:50 AM by chrisinnh

[joey_martin]

Use a ceiling plane to get the extra framing layer.

 

[chrisinnh]

Thanks Joey!

 

I had to adjust the height at the outside wall by the thickness of the rafter in order to get the ceiling to generate at the same pitch as the roof.While that works to an extent, as far as I can tell, ceiling joists are generated that follow the roof pitch, but they don't bear on the exterior walls.  They die into the studs.  Problems at the ridge too, as this is the structural layer.  The over-roof is strictly for insulation- the ceiling plane will need to rest on the plates.

Edited Tuesday at 12:50 AM by chrisinnh

[jorgearaya]

@chrisinnh you can use multiple roof planes stacked on top of each other, you'll need to edit the assembly layers to suit your project.

[chrisinnh]

Jorge- that's how I landed here to begin with!  Chief will not allow multiple roof framing layers.  It is possible to add a framing layer to the roof finishes, under the shingles, for example.  I tried that, too.  Shingles, plywood, fir framing, plywood.  Chief morphs that framing layer into the actual framing layer, no plywood between, and generates one fat rafter- that's what I see in a framing view.  In a cross section or full overview, the roof system appears to be floating by the height of the rafter.

Edited Wednesday at 12:25 AM by chrisinnh

[jorgearaya]

@chrisinnh I use multiple ROOF PLANES stacked on top of each other to create the main framing with exposed rafters and t&g, then I add another ROOF PLANE on top of the first one to create another "framing layer" or roof for my insulation and depending on the design I may add purlins for ventilation or another ROOF PLANE on top to create framing for my ventilation cavity. Does that make sense? In all I may end up with 3 or 4 actual framing layers that will auto frame. Now, much care should be taken if using multiple roof planes since they (the roof planes) don't interact well with each other when it comes to abutting certain edges as well as to how to finish the end or fascia with such a thick built-up roof. Hope that clarifies it.

 

Edited Wednesday at 02:18 AM by jorgearaya

[chrisinnh]

OK!  Got it, mostly.  Would be so nice to control this in layers- and adjust centers and orientation.  Seems like the software mod would be simple.  I can see all of the edges and edge detailing getting quite finicky.  Good thread you linked.  Per that thread, is there a way to turn trim off on the base plane trim and extend the exterior wall finish up?  Flushing the tails with the outside wall does not seem to do the trick.

 

The interior wall finish will obviously terminate at the top of the plate.