Roof not being created at correct height

[Christiaan]

If I create a roof on a design layer and specify the Eaves height as 0 it doesn't actually model it 0. Mine is 37.09 mm below Z=0. Anyone know why?

[CipesDesign]

Could it have to do with other settings? Overhang, Bearing Inset, Etc?

[Christiaan]

Don't think so. Overhang is 400 mm and shouldn't matter.

Bearing inset is set to be determined by Eaves height.

[Tom G.]

My quickie experiment in v.2013 Designer shows the roof tool working as advertised when Eaves Height is set to zero. Check your Organization palette to make sure your Design Layer elevation is set to zero.

[Kizza]

I think it may be that the roof tool is locked into a conventional (rafter) roof type of construction and that roof height calculation is somehow locked to the bearing height, even if the user selects Eaves Height as the controlling reference.

Setting roof height using Eaves Height should overcome this though.

Interestingly, in a trial version of Revit Lt, using the truss option the roof is set at my desired height that I specify (eg 2400).

If I change it to Rafter type, the roof drops down to allow for the birdsmouth by about 50mm. The roof is still set at 2400.

Another one for Needle & Mortar?

Edited May 12, 2013 by Kizza

[SonnyLuong]

I agreed with that. Check how your Story levels are set up. It's a new concept in VW that can really throw you off, but you can change the height of these levels via organization dialog box on the design layers tab like Tom has said.

[Christiaan]

Here's an example. The roof eaves height is set to 0. And I've drawn a (red) 3D polygon at 0. The eaves, however, is 37.09 mm below that line.

[Kizza]

Any chance for a 2012 file? Be interesting to see if it's a 2013 specific issue....

[Tom G.]

Christian: I tested again, setting by Eaves Height, and found your same result. Then I noticed that Vwks had auto-filled the Bearing Inset box with a number that I had not noticed. I zero'd this out and the roof once again showed correctly when regenerated. Could this be your issue?

Tom

[Christiaan]

Any chance for a 2012 file? Be interesting to see if it's a 2013 specific issue....

[Christiaan]

Christian: I tested again, setting by Eaves Height, and found your same result. Then I noticed that Vwks had auto-filled the Bearing Inset box with a number that I had not noticed. I zero'd this out and the roof once again showed correctly when regenerated. Could this be your issue?

That's it. I couldn't get my head around the hierarchy. In the example attached in this thread I set the bearing inset to 388 mm (which is thickness of wall). If I zero it out the eaves ends up too high.

I think the problem is my expectation is that the eaves should be at the top of the setout hierarchy and the bearing inset dimension should float.

As it stands you have to set your pitch, eaves height and overhang and then adjust the bearing inset manually to get it to the eaves to the height you told it to begin with.

[Tom G.]

Bearing Inset is a function of whether the roof is hand-cut (stick-framed) or is created from trusses. Is there a birds-mouth (in the local vernacular) cut out to create a minimum (or more) bearing surface or does the roof sit directly atop the wall with no rafter cut as it would for a manufactured truss?

The above roof type and the decision of how the member bears atop the wall typically requires the Bearing Inset field to be one of the first settings I address.

Tom

[Christiaan]

Yeah you're right. We call it a birds mouth in NZ too and it is important. I'm doing an early design model so not so the actual eaves height is more important to me at the mo.

Something needs to change though. For instance if you go to Edit Roof Settings in the above example the Eaves height says 0, but it's not 0. If you measure it it's -37.09 mm.

I think it's another case of a tool being written by programmers instead of designed by architects.

[RDS Casa]

This is still odd for me. I have a roof layer, its elevation relative to the storey  is 0. All the walls on the layer below in the stack, (that layer also associated with the correct storey), are set to have a top bound of 1500 (wall plate height in this case). I'm trying to make a very sleek clipped form here, where the roof edge has no over hang (with inboard hidden gutters). I've made a gable ended pitched roof from 4 simple walls. I set the eaves over hang to 0.  and the end condition to horizontal, But... 

 

If I set the bearing height or the  eaves height to 1500 (which should be the same when the cut is horizontal and there is no overhang?), the roof does not sit at quite the right  height? Also playing with the thickness effects it, as does the bearing inset. In the end I had to do a trial and error approach with there bearing inset to get it at the right height?

 

the wall thickness is 425, the roof is 440, the bearing inset was 247.5 or close to it. 

 

Is there any guidance on the relationships here? I can't find any?  its not in the videos?

 

I think it really needs to set a setting out point, somewhere in the constriction (which It thought might be the inter section the inner face of the wall core and the roof line of the datum roof component) and then everything springs from there?  

 

The clipping of the roof components seems odd to. I'm not even going to try and get this working. 

 

Any tips or resources any one has, please point me in the right direction. Thanks

 

[RDS Casa]

FYI This is how the components turned out...

 

 

So partly right. Its on horizontal mode. Probably some roof components need to be vertical, some horizontal, but I don't think that possible.