How to stretch the top of an arch roof

Good morning! I am adding an arched metal roof to a building I’m designing. The arch part was very easy. I drew an arch over the building, offset it 8", closed in the ends, then extruded that face the length of the building. NOW, at each end of the roof I want to pull the top of the arch out 6’ to 8’ to add a little more flare. Thats where Im stuck…Ive tried everything I know to do with no luck…Help?

Turner Custom Home Plans

Depending on what you need you might be able to use the Scale tool. Or it might just be easier to draw a new arch. If you shared your SketchUp file so we can see what you’ve modeled and what you need to do it would help.

Unlike what @DaveR reads in your text I would say:

  • extrude the ends on both side 8’ extra in length.
  • use a grouped slanted face (on each side of the roof ends) that intersects the roof structure
  • apply 'Intersect Faces with … selection after selecting all
  • delete face group and unwanted basic geometry
  • close end of slanted roof structure by drawing an edge over one segment
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Thanks Dave, that would probably help alot!! I will add the file shortly


My design file is in Softplan but I was going to draw the roof in Sketchup (much easier) and import it into Softplan. The other sketch above the building somewhat shows what I am trying to achieve

So you just want to cut the ends of the roof off at the angle shown in the example above?

Hey Dan thanks for the reply! Thats definitely something I can try too…thanks!! I dont have quite enough experience with Sketchup yet to know what all options are available but I’ll get there some day :slight_smile:

Yes that’s it!

As @Wo3Dan indicated, draw a plane through the roof at the required angle. Select the geometry and use Intersect Faces. Then delete what isn’t needed.


Thank you Dave that worked perfectly!! And I very much appreciate the quick replies, Im not used to that with orther software.


Good deal and you’re quite welcome. Maybe you want to just switch to SketchUp. :smiley:

Dave, did you use the “section plane” command to draw the plane?

No. I just drew a rectangle and rotated it to the angle. I did use Push/Pull to extend the roof out beyond the angled face so there’d be some to cut off.

Another option for doing this involves using the Solid Tools. This requires that you make your roof a solid group or component and then model a"cutting" volume. Subtract then subtracts the cutting shape from the roof.

The neat thing about this option is that it can be faster and it makes it easier with more complex shapes. Example although not a roof. The yoke of this U-joint was initially a round volume with the necked down back end. I used cutting volumes to create the outside end of the yoke as well as the inner shape.

Dave, when I deleted the plane etc it left an open end on the arch. How do I close that?

Trace an edge segment with the Line tool. Did you make a group of the roof before you did the intersection?

Yes I grouped the cutting plane and then the roof. When I deleted after the Intersections the whole roof went lol

Putting geometry in a group container protects it from being modified by other geometry. Notice in my example using Intersect Faces the geometry for the roof and the cutting face are loose geometery. In other words, in the same context. If you want to use the Intersect Faces method and you’ve grouped the roof geometry, you need to open the group for editing and add the cutting face geometry.

You should spend some time going through the instructional content at

To intersect with a group it is often easiest to draw the intersector at the exact place but outside the group, using inferences to locate and align it. Then copy or cut it, open the group and do paste in place. Do the intersect while the group is still open.

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I got it now. If you had said, select all faces that are connected I would be through by now lol. That sliced the roof and left the closed edge like I wanted :slight_smile: