Custom Truss difficulty


RichM1
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Summary: We're creating a vaulted tray ceiling in a house that started as a double-wide mobile home. I want to model the existing "trusses" so that I can figure out how to do the rafters to frame out the new ceiling. I cannot figure out how to do this though. 

 

Details: 

This house started out as a double-wide mobile home. It's been remodeled several times, huge portions added, walls rebuilt in places, rooms moved, walls removed. But the roof structure through the middle of the house is a 2.5/12 pitch, framed as follows: 2x2 rafter, 2x2 joist, 16" OC, with 12" pieces of 1/4" paneling used as gussets every 12". The tall wall has 1/2" plywood as a ridge beam.  I attached a drawing that shows each side. 

 

I tried changing the rafter and joist settings to 1.5" x 1.5", but it insists on building roof framing with 6" rafters floating above the walls, and framing the tall wall with studs that are in the room wall below. 

I tried to manually draw the framing in like the CAD detail drawing I attached, but I can't figure out how to rotate the 2x2 rafter to the 2.5/12 pitch angle. I figured I'd draw one "truss" manually, and then replicate/copy it across every 16". But after about 6 hours (admittedly I'm new to this app) I still couldn't figure it out. 

 

I put both sides together, and added the 2x6 rafters and 2x4 cross brace. Then we plan to cut the trusses back flush with the rafters and brace. The wall will be coming out of the middle. There's no code here, unincorporated county, so no building inspection to send this through.

 

Is there a way I can take this CAD drawing and use it for the actual rafters - extrude the 2D shapes into 3D? 

Truss.JPG

Truss with new rafters.JPG

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3 hours ago, RichM1 said:

Is there a way I can take this CAD drawing and use it for the actual rafters - extrude the 2D shapes into 3D? 

Yes. You could convert those shapes into solids. I expect that there'd be better ways using Chief's framing tools...but if you're unsure how to use them then that's not helpful.

For more help, post your plan. For even better help, you might consider paying someone to do some of this for you.

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7 hours ago, RichM1 said:

Is there a way I can take this CAD drawing and use it for the actual rafters - extrude the 2D shapes into 3D? 

 

The Truss Detail once made in Chief , can be dimensioned full size with no issues , in fact the whole thing is quite do-able in chief without the manual "framing"

as Chief will make trusses etc.....just might take a bunch of "learning" to get to that point in X12....... Draw the DW up just like it is built ..... then read up about

roof trusses and ask more questions .... While I could post the Plan I am not sure you'd learn anything that way ........ 

 

PS Chief always builds "normal" Roof Rafters , you then need to use the Roof Truss Tool to manually draw the truss in , then multicopy it..... do the

truss Editing 1st though ie your custom Truss.

 

image.thumb.png.a2378d4431c107bbef2f715fd8643bb1.pngimage.thumb.png.22e0e292a74e0431cf2b420321c91ff8.png

image.thumb.png.bfae30f07bbb6a903609f8eb953cc44a.pngimage.thumb.png.63c2ca32a48359d5de29997d098884f1.png

image.thumb.png.ab5ed25a90badbadcdd3c684a9c14307.pngimage.thumb.png.f5d152593322ba3f89b6c0b20ef012ea.png

 

image.thumb.png.f4fce93c967f3f219cd7ae5e7321ea49.png

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Thank you Mick for your long response and drawing that up! The issue I had creating trusses was trying to get rid of the webbing and specify gussets instead - it has the gussets made from paneling. I thought maybe if I used rafters, I could then add in the gussets manually... the one rafter setting I couldn't figure out how to change was rater depth determined by roof size. I'm still messing with it. The CAD drawing is accurate to 1/4 inch or so, changing that to a solid and replicating it would probably meet my needs, but I haven't had time to explore that option yet today.

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18 hours ago, RichM1 said:

Thank you Mick for your long response and drawing that up! The issue I had creating trusses was trying to get rid of the webbing and specify gussets instead - it has the gussets made from paneling. I thought maybe if I used rafters, I could then add in the gussets manually... the one rafter setting I couldn't figure out how to change was rater depth determined by roof size. I'm still messing with it. The CAD drawing is accurate to 1/4 inch or so, changing that to a solid and replicating it would probably meet my needs, but I haven't had time to explore that option yet today.

 

The Gusset could be done with Polyline solids I guess but do you really need to model them?  and just for the record I am not sure it a good idea doing what you are doing , you are cutting ALOT of the roof structure out, but I'm not an Engineer just a Builder of many years. 24' is a long span for essentially a 2x6, skinning the truss both side with 3/4" ply may help 

 

You cannot "specify" gussets in chief , but playing with the Webbing material width in Framing>Trusses may let you fool the program somewhat ?

 

The Webbing and Chords can be either modified by altering the truss envelope and then deleting individual members as I did above but you cannot Add webbing ...you can however copy and move existing members though. ( see PDF note below for more info found here on the Forum)

 

Rafter Depth is set in the Build Roof  > Structure Tab under Structure Area on right > Edit button or if the Roof planes already exist uses the Edit All Roof planes Icon instead then follow above instructions. It can also be setup in the Defaults>Framing>Roof 1st if not Built yet.

 

Truss Editing.pdf

https://www.chiefarchitect.com/videos/watch/348/framing-a-cantilevered-truss-roof-system.html

https://www.chiefarchitect.com/videos/watch/345/setting-truss-defaults.html 

https://www.chiefarchitect.com/videos/watch/9914/focus-creating-trusses.html

https://www.chiefarchitect.com/support/article/KB-00981/creating-roof-trusses.html

https://www.chiefarchitect.com/support/article/KB-00032/creating-an-energy-heel-truss.html

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On 4/23/2020 at 8:29 PM, Kbird1 said:

image.thumb.png.f5d152593322ba3f89b6c0b20ef012ea.png

 
I'm not sure if I'm following which of the many trusses shown is being considered, but this one is downright scary.
I'd recommend the tie be 2/3rd the span... which won't get the desired cln'g height.  Go with a ridge beam instead if cln'g height is critical.
 

 

3 hours ago, Kbird1 said:

24' is a long span for essentially a 2x6

Yep...that's for sure.
Rich, if you're building this for someone else, and not going through an engineer or a building department you're taking a big risk... I recommend you be extra conservative.

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Well, I'm working with the owner of the house, who is also a GC with almost 40 years of experience. We're gluing and screwing the 2x6 rafters to the existing 2x2 trusses+gussets, then cutting out the truss parts that extend below the rafters. It does seem like a wide span to me too, for 2x6's on a 2/12 pitch (I actually re-measured the slope), especially given the walls are 4" not 6" as well. The length of the wide area is... ok gonna go measure that lol... 16'. So there's a 16' stretch in the front where there will be some amount of outward pressure on a 4" exterior wall. There is no code or building department here, so it doesn't have to pass inspection... it just needs to not collapse.

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