Arch roof, 2 (related?) problems


I’m working on a home design, which is designed to be built (if Lottto Max ever pays out) into a south-facing hillside.The basic construction would be 8" concrete base & walls - only the south-facing walls have windows, the other windows and roof would be covered with an earth berm, shrubs, goats etc. The “Needs-a-roof model” illustrates the overall concept,
N.B. neither of these models is an architectural drawing - I call them “Concept illustrations”., which, if the project proceeds will become “Client’s Brief to the Architect”.

I’m having trouble modelling the roof, which may be a thin concrete shell, though technical constraints may change the construction details (to e.g. corrugated steel). It is shaped as an arch, primarily for aesthetic reasons.

The “before_pp_roof” model is where the problem(s) appear to begin
When I pull the thin sliver of the roof shell in the North wall of the “Before_pp_roof” mode to the South wall, either of both of these occurs:

  1. The roof shell is a vacant space, but it should be a thin solid shell ( thought I was pulling the thin shell’s cross-section to create the volume).
  2. I can’t get the upper part of the North or South walls into the model - I can see right through the arch area upper part from N to S.

Comments, hints etc welcomed.
Needs_a_Roof.skp (123.9 KB) <a class=“attachment”


Hi, I am not sure what you asking . But if its the void in your curved roof , then just draw one of the edges that makes it up and this will bring the face back.



Rather than getting all wrapped up in what’s gone wrong, just try it this way:


–Also: One thread per issue, please. You can edit or respond to your original post if necessary.


Thanks, Phil & Gully. I’ll be exploring your inputs tomorrow - my mind shuts down serious work after dinner.
Apologies for two postings, but I wanted to get the second model attached so did a new post to accomplish that… (New poster is limited to 1 attachment per post).


One attachment per post not per thread, so a second post within the same thread was the appropriate place to put your second model.
Now it is off somewhere in another thread, which makes no sense to someone who doesn’t see the two threads together.


The north and south walls have different radius is this by design or model error??


If by design, not mentioning it was pretty sneaky. Luckily, we have a mac7595 to spot such minutiae.

Aside from that though, I thought I’d mention that if you’d hold off with the window, you could take advantge of the structure’s symmetry by modeling only half then copying and flipping it. Could be a time saver and cuts your opportunities for making errors perhaps not quite in half. (In this case, of course, since the structure is symmetrical about two axes, you could just model a quarter of it.)

Of course, saving time is kind of a side issue when walls and ceilings are spontaneously disappearing.



No biggy if the radii is different. Extrude as Gully shown and adjust the arcs by tugging on the Arc cardinal point with the Move tool. There’s an animated example on this page under Add a Little Flare.


Not by design - I’ll investigate. I create the outer arc first, on the N wall, it sits on the E & W walls, then the inner arc - the arc height is set to a guide that is 19’ high. Then the North arch is pulled to the S wall, so it’s not obvious how they become different. But the idea of creating just a half or quarter is neat, and should eliminate whatever caused the error.
NB the small window in the S wall is just a temporary marker of where I am in the model. The other file shows the finished state. I’ll try to fix the problem where the 2 model files are in different threads.


Just to illustrate: