The definitive guide on walls in Revit: onion x stacked x composite (Post and Cons)
Modeling walls in Revit Architecture seems like a very simple task when it comes to a BIM platform . Replacing lines, arcs and circles in the AutoCAD representation with 3D parametric objects has given professionals greater flexibility and agility in their projects. However, doubts are beginning to arise about the best way to model each wall. Some users, seeking agility, end up choosing onion walls (those formed by several individually overlapping layers), others work only with compound walls (several grouped layers) and there are still those who refuse to give up stacked walls (one on top of the other). In this post, we will understand each style and reveal the positive and negative points of each workflow.
Types of walls in Revit
Before understanding each type of wall, it is important to know which BIM usage will be used for that model. You will have a different workflow if you are modeling for a budget or for an authored project (Architectural).“-What do you mean, Arthur?”Simple. When using Revit to model an architectural project, the user is not always concerned with modeling the construction system and equipment. The architect can spend more time configuring realistic materials while thinking about the rendering and presentation of the project. This is not necessarily true for the cost engineer, who can model a ceramic floor covering using the ceiling command above the structural slab (it is much faster to model this way and the program gives the exact area needed for the estimator to calculate the covering. However, it is not correct in terms of interoperability and other uses of BIM).
So there is a cake recipe?
No! What exists are good practices. As I mentioned above, depending on the BIM that will be used, the workflow may change considerably. This is why BIM Manager is needed to manage these processes. Over time, each user will develop their own tricks and tricks to gain speed in the process. This is why standards and guidelines are necessary to avoid creating grotesque models. And this is exactly where onion, composite and stacked walls come in. None of them are prohibited, but we need to understand their limitations before criticizing or praising them.
Author’s comment: I use a combination of the three, depending on the project and end goal. Composites are great for design; onions are great for small projects; stacked structures are best for budgeting . In general, I spend more time on stacked structures since building virtually is not just about modeling generic walls.
Let’s understand this better?
1) Composite Walls
“Like roofs, floors and ceilings can consist of multiple horizontal layers. Walls can be made up of more than one layer or vertical region (masonry, plastering, single mass, acrylic/running mass, paint, etc.).
The position, thickness, and material for each layer and region are defined through the wall type properties using the > Edit Assembly dialog box.
It is also important to note that for each layer we must assign a function with values between 1-5. The lower the value, the higher its degree of hierarchy in relation to other elements. For example: the Structure function [1] has a higher hierarchy than the Substrate function [2] . This means that in an intersection of a wall with a floor, the layers with the Finishing [5] and Finishing [4] functions of the floor will be overlapped by the finishing and structure layers of the wall since they have a higher hierarchy. See the image below to better understand this concept.
Note that when replacing the function of one of the floor layers from Finishing [4] to Thermal/Air Layer [3] the intersection between the wall and the slab is changed, since now the floor layer has a higher hierarchy than the wall layers, with the exception of the masonry structure.
2) Onion Walls
Onion walls are formed as horizontal associations of compound walls. For example, instead of having a wall with layers of masonry and cladding, we could have one wall to represent the masonry and another to represent the cladding (like the layers of an onion). In this way, the user could easily model ceramic cladding in bathrooms, for example. This workflow is often used when you want to represent a wall with cladding on one side that does not go all the way to the top of the slab.
3) Stacked Walls
Stacked walls are those composed of 2 or more subwalls stacked on top of each other. These subwalls can have different wall thicknesses at different heights and are attached with their geometries joined together. This type of wall can be used to represent, all at once, the mortared stone layer, the foundation beam, the masonry and its upper support.
Pros and cons
To define the advantages and disadvantages of each type, we need to take a construction system as a basis. In this case, we will simulate a building where the walls are composed of masonry + paint or ceramic coating. In this example, we will study the internal walls, where the coating only goes up to the ceiling.
*Another option would be to use the “Parts” command, but it is purely graphical and can cause problems in other budgeting processes.
Final Considerations
As we can see, there is no right or wrong way to model. The chosen flow will depend on the BIM Manager’s decision or your scope of work. For small projects, it is usually more interesting to use onion walls. However, when the project becomes more complex, this flow becomes unfeasible. Stacked walls are usually a better solution, but they will be a little more laborious at the time of modeling and the user will need to create a much larger number of types to achieve the same result. For beginner users, there is no great need to move away from compound walls. However, it is good to familiarize yourself with other solutions when new demands arise. If you are a more advanced user, invest in stacked walls. They may be the solution!
