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Editing roofs created by footprint

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    Editing roofs created by footprint

    I am trying to edit a roof which has two ridge lines. When I try to move one to the same place as the other the whole roof moves. This probably because when I select it I am not in edit mode?
    The only edit mode I can gain access to is edit footprint. But that is not very helpful because it only allows me to edit perimeter lines of roof which are actually offsets from plan below. If I had wanted a more editable roof I should have chosen edit by extrusion?

    The ridge lines are in different places because the walls in plan step about. I also keep getting the error message that walls are attached to roof. Do you have to detach walls from roof to edit the roof?
    Isn’t there a contradiction in that wall properties give you the option to connect it to a certain level. Which is then connected to, roof or level?
    Would it be better to trace over outline and create roof by extrusion?

    I have read that to align ridges it is possible to do it by creating a reference plane but is this really true?

    I think what you're looking for is the offset from base parameter while you're editing the sketch. This lets you set the point where each roof edge starts vertically so you can align the ridges. Depending on the shape of your roof, by extrusion might work, but if it's anything other than a single straight run, that might have it's challenges as well. You should not have to detach anything to edit the roof, although they might detach themselves if you move the roof away from the walls below.


      Sorry I do not see how altering the base offset parameter helps me. The building in question has a mansard roof with classic L-shaped plan suitable for terraced houses.

      Altering base offset parameter simply creates a new starting point for inclined plane of roof. Joining different terminations of inclined plane i.e. ridge lines, is what I want to do.


        Pictures might help explain what the issue is. On a typical roof changing the offset of one side will in effect move the ridge over. I don't typically do mansard roofs, but I'd try either splitting it into an upper and lower roof, or using modify sub-elements to specify the ridge lines. The issue with modify sub-elements will be the thickness of the roof will not be consistent, that may or may not be an issue depending on what you're using this for.


          This is Mansard roof where you draw part of the roof at say 75 degrees and then create another level and draw some roof plane at 15 degrees.
          An L shaped plan rather complicates matters.
          As you can see, the two segments of 75 degree roof at the back of the building rise to the same height. This means that when roof plane changes angle the ridge occurs at different places.
          But this generates at lot of problems regarding how small section of gable wall transmits load to the ground.
          It would be probably easier if small part of 75 degree roof continues to a higher level so that two parts of 15 degree roof are actually coplanar and continue to same ridge height.
          But how would you do that ?
          Attached Files


            Is this still the same project? If yes, use roof by extrusion tool as already suggested - see attached rvt file. If it’s an L-shape now, use roof by footpint tool and see this.

            EDIT: L-shape roof could also be done by extrusion by cutting the ends (vert. opening tool) at the intersection (see pic).
            Attached Files
            Last edited by PijPiwo; June 21, 2017, 01:30 PM.


              I have posted here on my problems with roof creation and some thought that Roof by extrusion was the tool that I should be using.
              The standard way of using this tool is to create a profile and extrude it.
              However, what happens if the profile needs to change at various points on its journey?

              Although the walls form an L-shaped plan, the ridge line does not change through 90 degrees. Hence the image by PijPiwo, though, received with gratitude, is not what I had in mind.
              If you look at my attached image you will understand what I am trying to achieve.
              I created a piece of mansard roof using roof by extrusion tool.
              I have used the vertical opening tool on my roof to cut out a portion of the roof out in plan. And I have added a second piece of 75 degree roof. Only problem is how to join 2 pieces of roof?
              I try join geometry tool and I make some progress. It removes “Boolean” part of small 75 degree roof and at least this gives us a valley line.
              So the only real option is Use conceptual modelling tools and model a void component in place.
              Architecture> Component> Model in place > void

              I start by setting a plane by picking a plane.
              I then start sketching a void which I can extrude.
              If you try to exit sketch mode at this stage you get an error message like this. Presumably voids are only allowed if they cut away from something. They cannot exist in a project in themselves.
              This is what I am left with ( image 26 07 17e) . I suppose I could use another void component to clean this up but surely there is a simpler way to clean up this junction?
              Surely at some stage I must join these two roofs or how else will I get a clean junction by attaching walls to roof ? ( it is not clean now).
              Does anyone have any thoughts on how to manage this work process?
              Attached Files


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