topic Re: Modeling roofs for trusses??? in Modeling

Modeling roofs for trusses???

Anonymous — Tue, 23 May 2023 13:21:37 GMT

I’m curious how the rest of the ArchiCAD community models roofs when they are structured with trusses? ArchiCAD’s roof tool is fairly powerful but does not have a good interface for “properly” defining roof planes relative to trusses and/or heel heights.

Modeling roofs for “stick frame” or basic rafter construction is very straightforward. Set the thickness of the roof to match the rafter dimension + roof sheathing – something like 5 ½” + ½” for a simple roof. Now, simply set your reference line to the inside of the stud wall and model away. The plate height (to story x) is easily set at something like 8’ (or 8’1 1/8” for more precision).

However….when modeling roofs for trusses, it’s not so straightforward. Composite thickness does not apply. I set the roof thickness to match the top cord dimension + roof sheathing – something like 3 ½” + ½”. I set the reference line to the outside of the wall stud. Now I need to adjust my (to story x) height if there is a special heel or raised heel condition. Nothing in the roof tool dialogue represents this kind of adjustment so I have to manually calculate the proper (to story x) every time – arghhhh! Its’ never a clean number so its always a problem if I am trying to properly represent the actual roof in relation to the rest of the building.

Note: If I am using a cantilevered truss with the bearing point/height equal to the eave/soffit height, I might place the roof reference line all the way to the outside edge of the roof.

This has always perplexed me…I’m curious what others are doing when modeling roofs for truss conditions.

Thanks,
Dan K

Re: Modeling roofs for trusses???

Brad Elliott — Tue, 13 Feb 2007 19:09:12 GMT

I do it the same way and wish there was an offset height setting.

Re: Modeling roofs for trusses???

Anonymous — Tue, 13 Feb 2007 19:39:42 GMT

Hi Dan

I was also wondering how to model the facia and side rakes on a gable roof. If you are using a 4" top cord then your side rakes also come out as 4" but should be 6". Then the facia comes out to about 5" for an 8/12. And changes for different pitches.

Brian

Re: Modeling roofs for trusses???

Steve Jepson — Tue, 13 Feb 2007 19:52:30 GMT

Personally, I don't fuss with the roof any more than what it takes to generate a roof plan and preliminary elevations, until I have the truss plans.

When I get the truss diagrams back, I use the magic wand to create a few precision 3d trusses. In section I move the roof (roof sheathing) and fascia up or down a little to match it.

I make roofs the same for stick framing as I do for trusses, they are just the sheathing.

Sometimes I use the profiler to add the metal drip edge,fascia, gutter, soffit, frieze, etc...

Re: Modeling roofs for trusses???

Steve Jepson — Tue, 13 Feb 2007 19:54:59 GMT

BAS wrote:
Hi Dan

I was also wondering how to model the facia and side rakes on a gable roof. If you are using a 4" top cord then your side rakes also come out as 4" but should be 6". Then the facia comes out to about 5" for an 8/12. And changes for different pitches.

Brian

I use a rafter for the gable end fascia and trim sometimes.

What I do most often in create it from my elevation.
In your elevation add a few lines to make the correct outline of your special fascia and trim.
Then copy and paste it into model view.
Set a slab thickness to the thickness you need. Use the magic wand to fill the area of your fascia.

View the fascia/slab in 3d (top view) save as .gsm
Now it is a library part. place it in the drawing. go to elevation and raise it up or down to fit the roof.

the trick to this is to draw a little slab next to your facia/slab and include it in the 3d view so you can click on it to get a true birds eye view of the fascia/slab.

This is basically the same way you make trusses from the manufactures' diagrams.

It may sound a little awkward but it is really quite easy and fast.

Re: Modeling roofs for trusses???

Anonymous — Tue, 13 Feb 2007 21:45:53 GMT

BAS wrote:
Hi Dan
I was also wondering how to model the facia and side rakes on a gable roof. If you are using a 4" top cord then your side rakes also come out as 4" but should be 6". Then the facia comes out to about 5" for an 8/12. And changes for different pitches.

Brian

Brian,
I use a special object for rake conditions - see attached image. In the image, the roof plane is 4" but the rake and subrake are 6".

Dan K

Re: Modeling roofs for trusses???

Link — Tue, 13 Feb 2007 21:46:21 GMT

Dan wrote:
This has always perplexed me…I’m curious what others are doing when modeling roofs for truss conditions.

Just whack it on and raise it in section.

Cheers,
Link.

Re: Modeling roofs for trusses???

Anonymous — Tue, 13 Feb 2007 22:02:17 GMT

Steve wrote:
Personally, I don't fuss with the roof any more than what it takes to generate a roof plan and preliminary elevations, until I have the truss plans.

When I get the truss diagrams back, I use the magic wand to create a few precision 3d trusses. In section I move the roof (roof sheathing) and fascia up or down a little to match it.

I make roofs the same for stick framing as I do for trusses, they are just the sheathing.

Sometimes I use the profiler to add the metal drip edge,fascia, gutter, soffit, frieze, etc...

Steve,
You must be building your own designs - It sounds like you have a modeling technique that works for you.

I explored modeling the roof as sheathing only but quickly gave up on it as the process did not easily reference from (to story x) in the roof dialogue...basically, I think we should be able to model roofs the way they actually "plate" from the structure.

As far as waiting for the truss diagrams to come back, I rarely have that luxury...If you're actually building the project you can probably wait...but if you're only designing it, then you have to "finalize your drawings earlier on.

Dan K

Re: Modeling roofs for trusses???

Anonymous — Tue, 13 Feb 2007 22:18:54 GMT

Link wrote:
Just whack it on and raise it in section.

Yup....that's pretty much what ArchiCad forces you to do. You would think that such a sophisticated software would have a better way of handling these conditions without having to resort to manual 3D manipulation.

Dan K

Re: Modeling roofs for trusses???

Jefferson — Tue, 13 Feb 2007 22:50:01 GMT

Dan -

Like Link and Steve, I set the roof as strictly the top skins. Thickness is usually choosen in reference to rafter tail thickness, and elevations are top plate heights. In it's early stages it's thick for visual representation, [read for the client's viewpoint]. The basic form, valley, hip, gable adjustments etc. and then once trusses/rafters are modeled, the up/down in section, [when I'm feeling "on my game", in 3D window.] The "thinning" of the roofs, 5/8" sheathing, + whatever roofing material buildup will be, and final elevation adjustments are a tail end process, once everything else is "set".

This is an extension of my model it as far possible, without going nuts, attitude. It yields nearly completed sections + elevations, plus it's RIGHT. That means no surprises on the job site, and then the only four letters used for my name are the original ones

Re: Modeling roofs for trusses???

Anonymous — Wed, 14 Feb 2007 06:44:16 GMT

I do often like this :

1. I draw my building without roofs
2. I draw an easy and fast section, but exact, over the building to calculate where the pivotline should be. The pivotline I normally have at top of my trusses so thickness of roof is the thickness above truss. (I would do this because I often use our officestandarddetails, if it's a more free building, then I do point 3 first before I make my section), and I'm an engineer, not an architect (Don't say ArchiCad isn't an construction tool, I've heard it alot, specially from AutoCad resellers, I've used it for that in over 4 years and don't want too hear that it's not possible to make constructions because, than I don't know what I'm doing last years )
3. I build my roof
4. I draw my trusses with Fill tool in section view and marked it and copy
5. I open "Create complex profile" and choose Create
6. I paste my fill into the new view and choose this to apply as beam
7. In plan view, I draw a beam with my own profile and the length of the beam is the with of the truss

This I think is the fastest way to create a roofplan with roof and trusses.

And, when comes the feature too build roof there pivotline is on top (or a thickness that has a negative value) ? We could change referenceline in walls, but not on roof..

Re: Modeling roofs for trusses???

Anonymous — Thu, 15 Feb 2007 14:07:51 GMT

Jefferson wrote:
Dan -

Like Link and Steve, I set the roof as strictly the top skins. Thickness is usually choosen in reference to rafter tail thickness, and elevations are top plate heights. In it's early stages it's thick for visual representation, [read for the client's viewpoint]. The basic form, valley, hip, gable adjustments etc. and then once trusses/rafters are modeled, the up/down in section, [when I'm feeling "on my game", in 3D window.] The "thinning" of the roofs, 5/8" sheathing, + whatever roofing material buildup will be, and final elevation adjustments are a tail end process, once everything else is "set".

This is an extension of my model it as far possible, without going nuts, attitude. It yields nearly completed sections + elevations, plus it's RIGHT. That means no surprises on the job site, and then the only four letters used for my name are the original ones

This is pretty much my approach also. Not trying to "go Nuts".

Jefferson, how are you modeling fascia? I tried the Cadimage #D Profiler with no success.

As far as the modeling Trusses question, I use the (not using AC10 yet) the AC "TrussPro" Object. There are no webs and I do not model them. In the Section views that show the truss I use the Polyline tool to "fake" the webs. I group the polylines for ease of copying & pasting to another Section view.

My one problem with the truss modeling is discussed here.

Also a truss discussion is here.

I will attach a few of my "going Nuts" with the Model.

Re: Modeling roofs for trusses???

Anonymous — Thu, 15 Feb 2007 14:08:36 GMT

Roof Rafters

Re: Modeling roofs for trusses???

Anonymous — Thu, 15 Feb 2007 14:09:34 GMT

The Fascia is made from little Roofs. Kind of a pain.

Re: Modeling roofs for trusses???

Anonymous — Thu, 15 Feb 2007 14:11:13 GMT

Here is a Section view with the Fake 2D polylines representing webs. Often not the True truss web either just a representation.

Re: Modeling roofs for trusses???

Brad Elliott — Thu, 15 Feb 2007 15:42:28 GMT

Jay,
Those drawings look good and are in line with what I'm doing except that I use a composite roof for the top chord to get me a quick fascia during modeling. I may be getting carried away with CYA but I don't show the webs anymore because they are always different so I just call out the truss with control points and say profile & web by manufacturer. Saves time and any more I prefer not to show it at all rather than show it wrong. Or worse yet have the truss manufacturer charge extra to try match my web pattern which is what started me down this path.

Re: Modeling roofs for trusses???

Jefferson — Thu, 15 Feb 2007 17:09:45 GMT

Jay -

I usually just use the roof tool, narrow it to the desired width, matching roof angle, very similar to Steve's explanation but I rarely save it as a .GSM, [probably should at least in the project library], only because I haven't invested the "time" to learn to drive the profiler correctly, and basically fascia, either raked of horizontal is either a roof or beam anyway.........of course now you can generate raked beams, [but I think they show strange in plan?]

Steve had given an excellent quick example of how he magic wands trusses, custom windows, and a few other things as I recall but can't remember where it was, [and really wanted to save that little diddy too!!].......Steve? He's got it down to wham, bam, perfect!

Re: Modeling roofs for trusses???

Anonymous — Thu, 15 Feb 2007 17:34:55 GMT

Brad wrote:
Jay,
Those drawings look good and are in line with what I'm doing except that I use a composite roof for the top chord to get me a quick fascia during modeling...

Brad,
You and I definitely model roofs for trusses the same way. Jay seems to model all the structure because he is an engineer. Steve and Jefferson seem to model roofs as a sheathing thickness because they add more detailed framing components later on in the process. (I guess this makes sense if you are GC'ing the actual design...are you guys (Steve & Jefferson) building your designs?)

I personally don't show an detailed framing info because I only produce "builders sets". I don't feel a need to spend extra time modeling the roof structure... After all, the truss manufacturer provides the truss drawings anyway.

I'm glad we've all had a chance to discuss our techniques here - they all seem valid to our specific processess...I feel like the roof tool, while powerful, is still underdeveloped...Looking forward to seeing posts with alternative techniques.

Dan K

Re: Modeling roofs for trusses???

Jefferson — Thu, 15 Feb 2007 18:10:01 GMT

Morning Dan -

Good thread you started here! No contracting here, my tool belt days are mostly over. It is that time that spent wearing one that drives me to "finish" the model as much as is reasonable, [we've seen that debated a few times here ]

My thinking is threefold: 1st the amazing ability we're provided through this program and because we can, 2nd in doing so it previews any problem areas and allows us to address them in the best way, before we actually get there. Along that path the solutions have greater range, and we are better able to participate in the ultimate decision. 3rd, and perhaps the biggest reason, basically this is exactly what we get paid to do, some very handsomely. Figure it all out while it's still virtual and affordable to solve.

Those flat-cadders and hand drafters who don't follow through on their designs, it is beyond my comprehension how/what is charged for an incomplete service, especially when the technology is available. It borders on criminal. A tad overreactionary to be sure but I have been the guy on the jobsite trying to solve a problem one of these folks had already been paid to do. Pushed my own button there, sorry........

Re: Modeling roofs for trusses???

Anonymous — Thu, 15 Feb 2007 19:18:54 GMT

Jefferson wrote:
Morning Dan -

Good thread you started here! No contracting here, my tool belt days are mostly over. It is that time that spent wearing one that drives me to "finish" the model as much as is reasonable, [we've seen that debated a few times here ]

My thinking is threefold: 1st the amazing ability we're provided through this program and because we can, 2nd in doing so it previews any problem areas and allows us to address them in the best way, before we actually get there. Along that path the solutions have greater range, and we are better able to participate in the ultimate decision. 3rd, and perhaps the biggest reason, basically this is exactly what we get paid to do, some very handsomely. Figure it all out while it's still virtual and affordable to solve.

Those flat-cadders and hand drafters who don't follow through on their designs, it is beyond my comprehension how/what is charged for an incomplete service, especially when the technology is available. It borders on criminal. A tad overreactionary to be sure but I have been the guy on the jobsite trying to solve a problem one of these folks had already been paid to do. Pushed my own button there, sorry........

Jefferson,
Glad you like the thread!..I think we are all benefiting from the diverse solutions. I'm especially appreciative of the opinions from individiuals like yourself who actually have field experience...The more "toolbelt" people we can involve the better!

Here's my response to you points:
1. I agree, ArchiCAD gives us some powerful tools to explore/document design issues.
2. Again, I agree...better to explore and find discrepincies before they arise.
3. Hmmm, I don't know if this applies to everyone...I get paid to do builder's set... anything beyond is money out of my pocket. I think this gets back to your first point about modeling it because "we can" If I'm not paid to do it I can't afford to do it. I know some/most clients expect it, but I guess it centers around what your contract actually requires.

Dan K