Roof intersections

I am trying to prepare a drawing of a gazebo for the HOA.
But first I would like to model the north side of the building including two roofs
The gable roof over the garage has a 7:12 pitch
The hip roof over the living area has a 6:12 pitch
The ridges of the roof meet at some elevation.
The hip roof is cut by the green-blue plane located at the edge of the gable roof.

I have twisted things up considerably in the attached file.

I would like to read 3 (or 13) easy steps to intersect these roofs.

thanks
js

1350 template.skp (210.1 KB)

The forum has screwed up your text so I can’t read it but I’ve had a look at your model. The larger gable end is drawn off axis as are the lines extending from it.

An easier way to model roofs like this is to use Push/Pull to extrude the gable end into 3D roofs (after making sure they are correctly oriented) and then use Intersect Faces to intersect them. Erase what isn’t supposed to be there.

Dave,
Thank you for your quick reply. I tried push-pull but i did not know about intersect faces. I will redraw.

I don’t know how i damaged the text but i am reposting here so I can read it.

I am trying to prepare a drawing of a gazebo for the HOA. But first I would like to model the north side of the building including two roofs The gable roof over the garage has a 7:12 pitch The hip roof over the living area has a 6:12 pitch The ridges of the roof meet at some elevation. The hip roof is cut by the green-blue plane located at the edge of the gable roof.

I have twisted things up considerably in the attached file.

I would like to read 3 (or 13) easy steps to intersect these roofs.

thanks
js

1 Like

It’ll be a big help to start over making sure everything in on plane. Watch the inferencing indicators as you go. If you have difficulty getting things lined up you might start by making a large rectangle on the ground plane and extruding that up to form a box. You can then draw the gable ends on the sides of the box. Then erase the box leaving the triangles for the gable ends.

I will try the large box idea. How can I force the gable ends to be on-plane? the top of the box will certainly help me get the roof ridges on the same plane. I have used another program that had a "snap to plane feature. Is on-plane automatic in this program?

You can use inferencing to make sure things are on axis. Watch for the line following the cursor to be shown in the color that matches the axis it is parallel parallel to.

Creating the box first gives you a guide to use for on-axis modeling. As you get familiar with SketchUp, though, you shouldn’t need to draw the box first.

Thanks again, Dave.
I’m sure i will need the big box for some time.
It will take me a few days to try to implement the idea and get used to inferencing.
js

One other thing that I would suggest is that you change the Camera to Perspective. The model you uploaded is set to Parallel Projection. SketchUp is designed to be used in Perspective view. it’s much easier to control the camera that way.

Perspective:
Screenshot - 4_10_2021 , 1_34_20 PM

Parallel Projection:
Screenshot - 4_10_2021 , 1_34_31 PM

I drew the big box but, of course i cannot see the wall geometry.
Is the idea to delete the big box faces?
how will the big box edges force the gable ends, to be drawn, on-plane?
i’m not sure about the big box idea

1350 Gazebo v2.skp (200.2 KB)

Yes.

With the rectangle drawn on the ground plane, the sides of the extruded box will be on plane and square to each other. That’s just basic geometry 101.

Thanks. When i drew a big box i do not see any reference geometry like the walls on the face of the box. How did you draw the triangles on the big box face?.

I did manage to draw 2 triangles on plane and extrude them. Your guidance to select extruded faces and then right-click and intersect selections saved me a lot of thrashing around. thanks.

Then when i deleted unwanted geometry I had holes above the southwest porch. I tried to draw faces over the holes with only some luck. (I painted the offending area maroon in the attached drawing.)

My new question is: Can I constrain a line to lie in any plane and then project that line off the facet to be perpendicular to some edge? I wanted to draw a line in the given red-green roof plane and project it to a blue edge in the green-blue plane. (the maroon area) Also, i end up with an edge on the roof that i don’t understand.
thanks js

1350 Gazebo v3.skp (2.5 MB)

I’m not sure what reference geometry you are referring to. The sides of the box make the reference geometry to aid in locating and correctly orienting the gable ends of the roof. Note that with some practice you shouldn’t need the box and I only suggested it as a simple guide to get you on your way.

I used the Line tool to do the drawing. I used the Protractor tool to set out some angled guidelines from the ends of the horizontal line. I set them to match the pitch of the roof.

It looks like you managed to get a reasonable representation of the roof. If you zoom in close to where the two ridges meet you’ll see one ridge is very slightly higher than the other. If this represents the way they actually are or will be, that’s fine but if not. It’s probably worth dealing with.

That’s an interesting part of a roof like this. The exact solution depends on what is supposed to happen with the building underneath. Note that the roof has no thickness as it is. Maybe think about how the roof would really be built and model that. Are there fascia and rake boards around the edges? Should there be a wide soffit under that corner? Or is it open to the rafters? All those sorts of details come into play.

Yes you can. If the line you want to draw is parallel to an axis line, just watch for the colored trailing line. If you want to go perpendicular to an existing edge start the edge, then hover over the existing edge for a couple of seconds and move the cursor away watching for the magenta inference color and the Perpendicular message. Either Perpendicular to the edge or to the face.
Screenshot - 4_15_2021 , 5_11_57 PM

Screenshot - 4_15_2021 , 5_12_42 PM

You might want to have a look at these on inferencing.

Thanks for the extensive compilation of thoughts on roof building.

I will study your references.

I agree, some of the real world conditions - like a roof with thickness will solve my problems.

In real life, the two ridges are slightly offset – a construction artifact I guess.

And, again I agree, I need plenty of work on inferences.

Thanks for your help

js