mtldesigns

Underside of a roof plane

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Good evening fellow CA users.

 

Got a nice gig for a Florida house that required rafter tails.  That part was easy, but wondering how to put the painted board on the underside?  I added thickness via Roof Surface Definition but it creates under whole roof plane.  Just watched a couple training vids. too, and nothing noting this part.  I checked and unchecked a lot of buttons too on the roof dbx.. so I am thinking its a combination?

roof plane underside.jpg

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Not so sure that is an automatic function.  How are you doing it in real life ?  Usually that style is to show off your decorative t&g sheeting not OSB.

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This has been discussed before, and I was sure I'd made a suggestion concerning it, but could not find it.

 

I wanted 2 options.

 

1) Specify sheathing when there is no soffit material.

 

2) Allow for an additional layer between the sheathing and top of the exposed tail. I'll sometimes cut down the top of the rafter to accommodate the decorative sheathing so I can run the OSB over it. This thickens the exposed part so nails/screws don't go through, and makes the unsupported sheathing less likely to sag. 

 

 

As for your question, I've used multiple roof planes -- looks OK in a standard render, not so good in others.

 

 

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We will be putting a 3/8" painted beaded board (same as your T&G) in between the tails, attached to that OSB.       

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I put that thickness in the Roof Surface Definition and it looks great... but it does the whole plane, including the attic.  I guess that's not really a bad thing????  Still not right though.    

roof plane underside 1.jpg

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Looks like you will be installing 3/8" bead board polyline solid panels to get it all technically correct or just make that an entire roof layer under the OSB if sections are not so critical.

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Adding the 3/8" thk layer is what I just showed.  I will have to work around the sections.  Better to do this way than a poly solid.   

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Sorry my internet is slow but I have had to do psolid soffits for several situations that chief does not handle properly so it can be done.

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You could break the roof plane at the exterior wall. That is, use a separate roof plane for the overhang. Just copy the roof plane in place and make the two join at the roof baseline.

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That's what I think Eric was mentioning, and I thought the same thing too, two planes, same ptich.  I'm going to try a couple of these other options you all mentioned than the one I did, and see how it goes.  Maybe need to suggest again to Chief Eric?

 

Thanks all.  

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Per Eric's suggestion, I tried a ceiling plane for the underside of an exposed roof plane (used with rafter tails mainly), and it worked great (see attached).  Figured I'd let all know for future questions on how to do this.

 

roof plane underside 2.jpg

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Hey Eric, Chop.. and Charles.  YES, I am back on this, after I updated all the planes this AM.  

 

Had a review with builder, and he has informed me that he was not wanting rafter tails after all, but exposed rafters.  Almost the same thing, but not to Chief.  Yes, Chief will give you exposed rafters, but not at a different size than the main rafter.  In this case, my roof rafters are 2 x 10's, but the exposed rafter is to be a 2" x 6" with a vertical block.  I created a little test model, because I didn't want to mess with main project model anymore.  On this test, the only way I can get this to work is two different planes of the same pitch, butted up to each other (can't join) and it is ugly on the shingle side (see below).  I also tried making a custom rafter tail, but can not scale it to be a 6" (5.5") piece of lumber.  Any other ideas, or thoughts...  ugh!  Any other training vids besides the ones via CA?

roof plane exposed rafters.jpg

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Just did a quickie test plan and it looks like you should be able to do a transparent ( Insulation Air Gap ) soffit material and a 5 1/2" sub fascia and then manually delete the sub fascia.  The custom rafter tail seems like it should work but this might be easier.

Rafter tails.jpg

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Unchecked Soffit, Eave Fascia and Eave Sub Fascia.

 

Used a Rafter Tail. 

 

Note what may be a problem circled in red.

 

ct1.thumb.jpg.52bf9d3ce03f5244e5b5f661ee26bcfc.jpg

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R U SERIOUS?  That's exactly what I've been trying to do.  I noticed that when I had soffit's in, it did the cut...  Never would have thought insulation air gap can be used as a invisible plane.  That's thinking outside the box.  Thanks for helping with this frustration of mine.  I will hit it tomorrow

 

Stay warm Chop!

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The fire is on.B)   You might want to consider another look at the rafter tail theory as it may be a little cleaner overall.  I am not getting the artifact that Eric did and I am not really sure what that is.   The only issue I see is the soffit gives you a plum cut rafter heel and the rafter tail gives you a square cut rafter heel, if that matters.

 

Rafter Tail 6.12 DBX.JPGRafter Tails.JPG

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13 minutes ago, Chopsaw said:

I am not getting the artifact that Eric did and I am not really sure what that is. 

 

It's a rafter tail for the gable. I turned off gable fascia and sub fascia, so it should not generate -- but it does. 

 

Changing the tail profile gets you plumb cuts.

 

ct1.thumb.jpg.aa866f7544ec5d0eea47a5ae7f9b8257.jpg

 

It's been warm and dry here -- low tonight only 22F (-5.5C).

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8 minutes ago, solver said:

I turned off gable fascia and sub fascia, so it should not generate -- but it does.

 

Ok so you can not actually turn off the Gable Sub Fascia so you made is as small as possible and it created an artifact.  It seem that it can be deleted if necessary as I did with the Eave Sub Fascia in the previous soffit generated example.

 

The plumb and square rafter Heel cuts I was referring to in post 18 may not be the correct terminology but it is the area where the rafter is cut at the outside edge of the top wall plate that I circled in red.

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35 minutes ago, Chopsaw said:

but it is the area where the rafter is cut at the outside edge of the top wall plate that I circled in red.

 

You can use the tail profile to do this.

 

ct1.thumb.jpg.67c77f07e7fea592d4e37611cff1245a.jpg

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Hey thanks Eric.  It looks like that might even work to cut a proper rafter bird's mouth.  I will give it a try. :)

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Not done so quickly but as accurate as possible and it works but there seems to be an issue with the hip rafters.  As usual there is always something that breaks when you try to be more precise.

 

Rafter Tail Demo 2.zip

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