slope arrow - roof problem

[blumarble]

Once again I'm frustrated trying to get help from Revit Help; their are just too many variables that aren't explained in enough detail!
(see attached) I'm working on a low slope roof. I know the height at the head of the arrow/blue reference line, and the height at the tail of the arrow. The two slope defining line segments circled in green are only segments. I thought the arrow would define the fourth slope to match the heights I need (without creating another roof), but every combination I try comes back with the "can't create roof" error.
Maybe someone can tell me how to do this, and/or what each of the roof arrow parameters define?
Thanks.

[Graham Briggs]

Hi Blu,

Sometimes its just a matter of a fraction of an inch (or mm) that prevents the geometry from closing. Without having the actual geomtry to inspect (rvt file), I can only say, check your math...

If you can, post the file (or cut and past the relevant geometry to a clean project file and post it) so we can take a look.

Graham

[DoTheBIM]

I have to agree with Graham. If I knew I what the final general shape was to be, I could try to point you in the right direction. If you know the height at both ends of the slope arrow, would it be better to change the slope arrow contraint "specify" to "height at tail"... and then enter your levels and offsets accordingly? At an offset of 2'8 and a negative 3/8" slope it would take 85'-4" of horizontal space to your oposing slope to make a a roof work. if your oposing slope is also negative. Or are you after something more like the attached pic?

[kpaxton]

blumarble,

I would have to agree with DoTheBim - if the picture is what you're wanting, then perhaps this is the right method... but I would construct it differently. Again... I don't have a model to look at, so much of this is conjecture.

However - part of what I'm seeing, if I understand what you drew correctly, is that you've got two elements that are wanting to define the slope and they are in essence causing a conflict.

You have on one side a roof segment with a slope defining line. Opposite of this you're using a slope defining line on a parallel segment. These two may be 'cancelling' each other out. Try removing the slope definition on the one segment and use just the slope arrow on the other.

Hope this helps.
Kyle