modeling walls for construction in Revit

I'm not big on software "tips and tricks", mostly because I think there are a lot of people out there who can do much cooler things in Revit. However, I think I can contribute a few things, especially since Revit doesn't fully support contractor's efforts. In my last post, I discussed modeling philosophy and brought up the example of modeling walls. Here is how:

First, create a wall type in Revit for each layer. (in this case, "Basic Wall: CMU" and "Basic Wall: Gypsum"). Model each wall type as a separate object:

















Align the interior faces of the gypsum walls to the faces of the block wall (using the "align" command):
















When I first did this, I thought that is all I would have to do. Until I tried to put a door in the wall. Because Revit is "smart", it knows that doors don't span 3 different walls:
















So, join the walls (using the "join" command):
















Modeled for construction. Voila!

12 comments:

T_R_B said...

Besides myself, I have not heard of anybody else doing this. We have been using this type of walls for most of our exterior walls. Since we have projects that have complicated exterior finishes we choose to beak up the components. This helps with wall clean-ups. Our structural engineers like it that way also.

thebimman said...

Hi TRB,

I agree totally with your method of constructing walls and can confirm that some of our consulting engineers (in NZ) who are using Revit prefer this method also. I would like to start some dialogue with yourself, if you'd like to, to discuss various Revit 'modelling work flows'.

Kind regards

Jason

Richard Binning said...

Hi Laura,

Well said! This is exactly the type of modeling that is needed to provide the most meaningful data downstream. I'd love to discuss this further. Working in a design-build firm I face this debate on a daily basis.

Modeling to expedite the generation of construction documents is not always best for the BIM model or the downstream consumers of the data. We are working to maximize the work flow issue regarding ownership of objects, transfer of responsibility among disciplines, etc.

Current project: Revit Based BIM model (single rvt) constructed using Revit Structures, Revit Systems, and Revit Bldg.

David Baldacchino said...

Your thoughts regarding the different modeling "needs" by architects, constructors and operations is interesting. Yet, I don't see how if I model an exterior wall made up of 7 layers (gyp, CFMF, sheating, water proofing, rigid insulation, air gap, brick veneer) as one entity, that it cannot be re-used by a constructor. I can understand that you might require it to be in pieces in order to figure out construction scheduling, sequencing and critical paths, but for me, building a model this way is just not profitable. Perhaps a wall assembly, even though modeled as one element with 7 layers, needs to have enough flexibility built in so that you can still assign some sort of sequence/priority by which each layer is built etc., without having to model it as individual pieces. After all, in the end it SHOULD behave as one wall. We need this sort of flexibility if constructors are to take advantage of what we're modelling as architects.

I love this blog. Architects and Constructors need to collaborate more on this front. I think once we sort out liability issues etc, then we can really focus on the actual 3D model in its entirety instead of having to spend time breaking it up in the ol' 2d drawing format. I would love to see more debate/discussions about how we envision to see such collaboration go or perhaps even some of your personal experiences. At the moment we're still not spending the necessary modelling time to fully detail all conditions, because so much of our time goes towards the production of the 2D drawings. And as you might imagine, we don't model what's not shown in elevation.

Keep up the great work!

Laura Handler said...

I understand that most architects won't be willing to model walls like this at first. They don't see the benefit to modeling in such a time-consuming manner. However, as more this tool is utilized by more contractors, they will begin requesting it (until Revit comes up with a way to phase the layers with the wall object!).

We are working with 2 architects who use Revit - neither will model walls like this. However, one of them is allowing us to modify their model once it reaches a certain stage. It isn't an ideal situation, but at least we won't have to re-split all of the walls everytime they submit a new model to us.

Laura Handler said...

Richard,

Please feel free to e-mail me (or use the BIMForum (www.bimforum.org) to continue a discussion on this. I think that it is a very important discussion to have, and I would love to have access to your experiences!

I'm also interested in this Revit Structure/Building/Systems project that you mentioned. We are looking into Revit Systems, but are concerned about the limitations of the software.

Razvan said...

Hi there,

Interesting way of doing a wall, but it requires also new door families. Although the joined walls understand the opening in the door familly, the door itself doesn't see more than its won host. Therefore you'll have the frame(s) inside of one of the joined walls.

Razvan said...

Hi there,

Interesting way of doing a wall, but it requires also new door families. Although all the joined walls understand the opening in the door familly, the door itself doesn't see more than its own host. Therefore you'll have the frame(s) inside of one of the joined walls.
Can be fixed but tends to get tedious.

architect11 said...

As a contractor and an architect, I'm not quite sure what you're trying to accomplish by modeling this way.

Unless you're doing all of your takeoff in Revit and providing the contractor with the takeoff, conditions such as self-perform work (down to the drywall screw), exact heights of finish wall, TOW conditions and special bracing conditions can all be addressed through model linking to assembly database costs, which include labor, material rates, install efficiencies, component location, etc...above and beyond just the calculated area and count.

By linking assembly (model) to assembly (cost) you pick up efficiencies and are closer to how estimators perform takeoff, lf, sf, count, cy, etc..instead of taking off every unreferenced component that doesn't show the framing it's being anchored to. For example, is that 5/8" type x rock being attached to a 6" mtl stud or a 3-5/8" stud?... I wouldn't know with this method, because all I would see is that individual wall category.

I don't want to sound too negative though and I really see where you're going, but after about 22 or so projects the reality with BIM assemblies is that they do work, just changing process on the other end (estimating) instead of the modeling end....

Also I'm all for Revit drilling down to more accurate estimating within assemblies! Rebar, imbed plates,would be a great place to start..

Great discussion you have going though and keep up the good work!

brad said...

David B.,
As an Architect who models most exterior and some interior walls this way, I find it faster in the long run because it saves from managing 20 similar but subtly different wall types down the road. It simply makes sense for everyone involved in the process to model the building as it would be built and not as it used to be drawn.

It wouldn't be that difficult for Revit to have a tool to draw each individual layer of a wall simultaneously. It would sure save a lot of headache in the long haul.

Joey said...

If an estimator is concentrating their efforts with using QTO for model takeoffs, what do you think is the best way to draw walls or other components? I would think one would like the most information in detailed breakouts. What is your opinion? When collaborating with an architect in the preconstruction process, in your experience, is the best way to convey an estimators needs through modeling with Revit for multiple extractions with QTO?

Michael Ruehr said...

I use and teach similar modelling technique since 7 years.
I call it Model by Trade. The only difference to your suggestion is I only break up walls that are part of a different Trade or trade package.
For instance a complex Interior drywall is still modelled as one wall, as it gets scheduled and costed as one assembly. However a in place concrete wall with masonry cladding on one site and dry-wall cladding on the other would be 3 Walls.
The extra modelling effort is easily offset by better control over join condition’s and selective vsibility control.