Roof/rafter constraints, someone have a method?

[Kroke]

I've been trying to do roofs with 2x rafter systems under the roof skin pretty successfully until somone decides later on in the design process to change the roof pitches, arrrgh!

I use a 1" roof, and then create rafters as structural members. If I try while in sketch mode to lock the top side of the rafter to the bottom side of the roof and then offset (for the bottom side of my rafter) the appropriate distance ( 8" for a 2x8 ), and lock it with a dimension, when I change the roof pitch, theoretically, you would think that the rafter would adjust accordingly since it is locked to the bottom of the roof plane. Wrong
I've also tried constraining the rafters to a refrence plain with the same results. They don't seem to work.

Attached is a pic of what I'm trying to do. I have to change roof pitches here and there and none of the rafters will update after making the roof pitch changes.

Is there a way to do this correctly? Am I going about this entirely wrong?
If anyone has any input at all, I am all ears at this point.

Thanks in advance guys!

--JJ

[whittendesigns]

What I have done is create a line based rafter. You draw detail lines in 2d, then just simply select the lines. The rafter family you can make the pitch a type parameter, so if someone says change it, change the whole roof at once.

Don't bother attaching it to the roof skin. Do the framing, then align the roof with the tops of the rafters.

What the line based family does is take out the guess work as to the length, diagonal, cut, slope, everything. I did families for hips, jacks, and valleys too, It works pretty sweet. I haven't used it in awhile though. Still takes alot of time.

I think I posted the families here at one time somewhat recently.

[ford347]

What I've done is I draw my roof skin first, or the plywood roof or whatever you are using. That way you can use the roof to draw 3d structural members. I like to use beam systems if I can and check the 3d option in the beam system properties and use the roof as the 3d element to pick from. Draw all of your ridges, hips, valleys etc., first, using the roof as the work plane, then select all of these elements as supports for your beam system or individual placed members. The key with all this is that you keep the 3d button checked whether drawing a beam system or drawing an individual beam. This way, if your roof pitch changes, you can move your hips, valleys, ridges etc., back in the position they need to be, which can be kind of clunky, but all the members attached to them will follow. This won't happen exaclty automatically like I said, you will have to re-position your supporting elements back where they need to be, but it takes a lot of the work out of re-drawing everything. Play around with it a little.

Hope this helps.

Josh

[Kroke]

I'm not sure I follow either of these methods, but I'm willing to try.

[ford347]

Try the tutorial on using beam systems and try to get used to it. You'll get better with them. Also, when drawing a beam, click the 3d button and play with the results. Basically, what this is doing is snapping to elements already drawn and following their plane. Use the tab button when snapping to certain elements and watch what is highlighting as this really affects what plane your new beam is using. Play around with it and see what you can do. This may help you out although getting used to drawing with Revit building structural elements can be quite tedious at times.....or at most times tell you the truth.


Josh

[whittendesigns]

Pic #1. Draw simple detail lines in plan view. Attach them so if you increase or decrease the span the lines go with it. The detail lines are obviously view dependant so they won't show up in 3d.

Pic #2 is my line based truss for ease of understanding.

Pic #3 In the project, select the truss and use the pick arrow. Now just click on the detail lines and voila! Instant truss system that will shrink and expand with the detail lines.

Pic #4 If you want to change the roof pitch, hover over one of the detail lines, right click, select all instances, change the roof pitch, voila! 12/12 pitch on all trusses.

LOL, sorry about the voila's. You don't have to use the double roof system or make detail drawings. You will have an actual modeled roof system. I have to fine tune all my line based families before I post them, but the truss is a good example and they are quite handy. You can draw any roof using detail lines and just select the lines. You don't have to adjust length of the families becasue they are constrained to the lines.

[whittendesigns]

And the truss, sorry forgot to post it.