Complex or assembled families
in Revit: which to choose
When resolving a BIM family with a high degree of complexity, there are two paths: concentrate all its geometry and behaviour in a single file, or work with components that are assembled together. At A3D we call them high-complexity families and assembled families, and the choice matters.
Keep reading: the difference between the two and which to choose ↓
What is the difference between a high-complexity family and an assembled one?
Before choosing a path, it helps to be clear about what distinguishes each approach.
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High-complexity family Everything in one file
It is made up of multiple elements and components resolved within itself, which gives it greater functionality. A complex window family, for example, can have different types of glass, frames and closing materials — its internal complexity has no clear limit.
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Assembled family · A3D’s approach By components
It is a collection of simpler families grouped into a larger whole. A complete floor plan — walls, windows and doors modelled as independent families that are combined with each other — is a common example of an assembled family.
The complex family is a single family with multiple elements resolved internally; the assembled family is a collection of simpler families grouped into a larger whole.
Why an overly complex family can work against you
More functionality does not always mean greater ease of use.
Although complex families can be very useful, it should be borne in mind that they are sometimes too rigid: adapting them to a model requires a deep knowledge of how they were configured inside. That lack of flexibility can be a real obstacle when working on a BIM project that changes over time — and all of them do.
At A3D we favour not over-parameterising models. That is why we prefer to work with assembled families, using a method similar to building with Lego: linking several components together, instead of creating a single “super-element” loaded with internal variables that only whoever designed it can handle with ease.
Why we recommend assembled families
Although they may seem more laborious at first, they adapt better over time.
We recommend using assembled families whenever possible. Although they may initially seem more laborious to build, their speed of adaptation to change is far greater than that of complex families. This makes working much simpler on real BIM projects, where an element rarely stays exactly as it was designed on day one.
When starting out with the BIM methodology there is a temptation to create a complex element with many parameters and variables — a “super-door”, for example, where the leaf type, the opening, the number of ironmongery items and the architraves are all defined in a single family. Although it may initially seem a good idea, and sometimes it is, this method has a significant flaw: it produces very rigid families that end up hindering the team’s pace of work.
We prefer to work as if we were linking independent components, rather than creating a “super-element” with too many variables inside.
When a high-complexity family is the right choice
Neither approach is universal: the decision depends on how the element will be used in the project.
A complex family makes sense when the element genuinely works as an indivisible unit in the project — a manufacturer’s equipment item with closed geometry, which does not need to be combined in different ways depending on the case. In those cases, concentrating all the information in a single family can be more efficient than fragmenting it unnecessarily.
Outside those specific cases, working by components usually adapts better to the changes a real BIM project demands: a wall that changes finish, a door that goes from single to double, a piece of furniture that needs another combination of drawers. The question to ask before starting is not “can I resolve everything in a single family?”, but “do I really need everything to be resolved in a single family?”.
The rest of the series on BIM families
This is the third of four pages on how BIM families are designed, managed and applied in a real project.
Frequently asked questions
Complete answers to the most common searches about the complexity of BIM families in Revit.
What is a high-complexity family in Revit?
A high-complexity family is a single family that brings together multiple elements and components within itself, with all its geometry and behaviour resolved in a single file. A complex window family, for example, can include different types of glass, frames and closing materials: its internal complexity has no clear limit, and grows with every variant added to it.
What is an assembled family in Revit?
An assembled family is a collection of simpler families grouped together to form a larger whole, instead of resolving everything in a single file. A complete floor plan — with its walls, windows and doors modelled as independent families that are combined with each other — is a common example of an assembled family.
What is the difference between a complex family and an assembled one?
A complex family is a single family with multiple elements resolved internally; an assembled family is a collection of simpler families grouped into a larger whole. The first concentrates the complexity in a single file; the second distributes it among several components that combine as independent pieces.
Why does A3D prefer assembled families?
Because complex families, although useful, tend to become rigid: adapting them to a model requires knowing in detail how they are configured inside, and that lack of flexibility can become an obstacle when the project changes. A3D prefers to work with assembled families, linking components as if building with Lego, instead of creating a single “super-element” with too many internal variables.
When is a complex family preferable to an assembled one?
When the element really works as an indivisible unit in the project and does not need to be combined in different ways depending on the case — a manufacturer’s equipment item with closed geometry, for example. Outside those specific cases, working by components usually adapts better to the changes a real BIM project demands.
We do this work every day
Deciding when a family should be complex and when it should be assembled from components is exactly the kind of judgement we apply at A3D on every project, so as not to leave the model trapped in rigid “super-elements”. If your team needs to review its family library or needs specific Revit training to make better decisions of this kind, we go through it together on your project.
And your most complex families: what state are they in?
Tell us about your plant: an A3D specialist tells you in 15 minutes where to start, which area to survey first and with what scope.
Prefer to continue with the series? Read about BIM family management in a practice or go back to the difference covered on this page.