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What do you model in 3D and what do you detail in 2D?


Hey folks,

This question might be too philosophical for any meaningful suggestions (or my skill/knowledge level might simply be too low for me to understand what I'm really asking) but as a Newby to Archicad I'm struggling with what aspects of the design to model in 3D versus what what is simply detailed on a 2D drawing.  The origins of my confusion are that I'm coming from the mechanical product design world where there's no analog to Archicad's  approach to layers, viewmaps, layout books, etc.  In my previous life, EVERYTHING is modeled in 3D and 2D is limited exclusively to annotation of projected views and cut sections.  We had a saying - if it's not in the 3D model it doesn't exist.  

In retrospect this makes a lot of sense - in the mechanical product design world, products are almost exclusively produced by computer numerically controlled equipment (or by tooling produced by CNC) directly from the 3D CAD data meaning that drawings are relegated to inspection information, tolerances and assembly notes.  But I realize that in the architectural / building world - particularly in residential, the "drawings" are fundamentally how stuff gets built and there is most certainly a law of diminishing returns for additional 3D detail - especially where you want to builder to have some "preferred practices" flexibility. 

Assuming that my decision on what to model in 3D versus document in 2D is NOT driven by the desire to create more realistic or compelling client images - but rather is driven exclusively by what's the most efficient and effective way to communicate design intent to the contractors/builders - what calculus to you use to determine what to model in 3D?  

I'm fighting the urge the model everything in 3D but increasingly realizing that might not be the most efficient path with Archicad.

Any words of wisdom, suggestions, examples, horror stories, etc?? 


I model everything in 3d.

Karl Ottenstein

I don't model rebar, nails and screws or wall studs/headers... but some do.  I do model almost everything else down to j-bolts/hold-downs, joist brackets, etc.  Consider that all of this stuff will show up in multiple views and that 3D views (via 3D Drawings) should be considered as integral to the delivery package as the historical orthogonal views (section/elevation, plans etc).  Also, if it is modeled, it can be scheduled.


That said, for preliminary design, I wouldn't go into that level of detail - using a composite for floor systems, etc.  And if a client is on a tight budget, design development might just stay abstract for speed/cost.

One of the forum moderators
AC 27 USA and earlier   •   macOS Ventura 13.6.7, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB

The key point you make is the purpose of the model. It is a design intent model for you and most Archicad users to communicate the design intent to building contractors. Some other users have different uses that require additional modelling.


My approach is to model elements to a level of approx 1:20 detail level. This means that the model will look right in BIMX and detailed room elevations. Modelling too much detail on larger projects will generate way too many polygons and will take more time than the beneficial outcome. 


But as I stated at the start, everyone's process will be different based on the deliverables. And a good thing to do is to test it out over a few projects. Track your time on each project and see where doing things in different ways will save you, or cost you more time. 

Nathan Hildebrandt fraia
Director | Skewed
AC6 - AC27 | WIN 11 | i9-10900K, 3.7Ghz | 32GB Ram | NVIDIA GeForce RTX

The old rule of thumb used to be model as if your output was 1:50, Nathan has suggested 1:20 which may be more relevant these days as technology has advanced. The basic principle is - if you can't see the element at the presentation scale there is no need to waste time modelling it. You can then cover the shortfall in information through 2D details, overlays on live sections or simply notes/annotations.


There is the BIM aspect to consider, but again it depends on what you want to document.


And don't get suckered into the "digital twin" for construction, that isn't going to happen for a very long time. I believe it has already been toned down to a "digital shadow".

Apple iMac Intel i9 / macOS Sonoma / AC27UKI (most recent builds.. if they work)
Eduardo Rolon

Additional rules I use besides the scale:

  1. If the element is shown in 3 or more views you can model it.
  2. If the element is critical for design/coordination then model it (i.e. Reveals/Joints)
Eduardo Rolón AIA NCARB
AC27 US/INT -> AC08

Macbook Pro M1 Max 64GB ram, OS X 10.XX latest
another Moderator

I agree

Tim Ball

AC26, iMac

User since V5

Sorry to belabor this forum item but i could really use some stylistic help from this group! Here's an example where i could use some advice on modeling strategies!!!!... 

The following illustration (not from Archicad) shows approximately what I'd consider to be fairly typical basement wall construction around here (although basements are generally cast concrete as opposed to block). 

I'd like to convey this information in my model and communicate it to the contractor in the best way possible.  I'm still very unclear on what goes into the 3D model and what is NOT modeled in 3D but is detailed or annotated on the 2D section views. For example... 

a) Would you 3D model the thin sheet metal flashing used as a termite shield?  If so how do you do this assuming it's like 1mm (.040") thick?  If you do model this in 3D, would you put this in the basement wall complex profile - make it its own complex profile or do it some other way (that I don't understand!).

b) In general - how do you model thin profiles like membranes? Do these appear in the 3D model or are they only noted in a 2D drawing? 

c) I keep hearing reference to people "modeling" things like joist hangers and threaded anchor rods. Forgive my ignorance here but I haven't figured out how to draw up discrete components such as these in 3D in Archicad!!  So far the only thing I've done in Archicad 3D are extruded profiles such as walls and beams. How does one create and place 3D models of these - or are these not modeled by the architect/engineer but downloaded from some library someplace?

I really appreciate the insight - seems like there are a million ways to do things with tradeoffs and I really value learning from people who have consider them and the implications. 

Thank you!!!!  



My approach would be as follows.


a) Depending on the complexity of the building and the number of details you were wanting to cut through it would determine if it was modelled or not. Based on the detail above I wouldn't model it, as it wouldn't be seen in my sections, as it is too small. But if you were going to cut a lot of details at a large scale, then model as a separate complex profile on top of the basement wall. That way it can be separately labelled with autotext calling out its profile name (which you name appropriately).


b) I will only include them in composites for walls (I then have a wall schedule that the builder can than review and know exactly what needs to go into each wall of the building. 


Here is an example that I use on every project. I then have a wall label that takes the start of the Composite name to tag each and every wall.


c) Unless there is a real specific reason for modelling connections, I don't model them as they are not adding value to the model. That being said, I know how much space I need to leave clear for bolt heads and threads and nuts around structural steel. A graduate or a newly registered Architect without my experience may need that, otherwise they do get some surprises on site when the see steel fixings and brackets poking out.


Nathan Hildebrandt fraia
Director | Skewed
AC6 - AC27 | WIN 11 | i9-10900K, 3.7Ghz | 32GB Ram | NVIDIA GeForce RTX