How to start a family

[rbcameron1]

Well, I know how to start a family, but I'm talking about Revit here! ;)

It's 2015, how do I model a family? What's important and what isn't? We're reaching the point where a 500kb - 999kb family really isn't as big of deal as it used to be. Our models remain nimble even over the 300Mb + mark. (Yes, now is the time to comment about your glorious 1.4Gb model)
It still seems like there are a lot of varying opinions on this, so I thought I'd try to get a bead on what people are thinking.

So what is important?
How about including a cut-sheet PDF with verified dimensions and information? To me, this is critical. You can model it all you want, but if you can't point to what it is in reality, you're just blindly modeling and no one will trust your model.

Alfredo Medina has an excellent post over on the revitforum.org site. My comments are in Red. Feel free to add to the dialog.
http://www.revitforum.org/architecture-family-creation/19501-do-you-have-any-difficult-family-needs-go-emergency-room.html#post113772

Plan the family. If necessary, make a scheme with bubbles and arrows.
Define the scope of the family, and don't do more than that. (scopes can change, make sure your model can change with them)
Instead of making a super family that pretends to do it all, do a set of families that serves one purpose at a time.
Instead of long formulas and several visibility parameters, use types.
Instead of creating many types, use type catalogs (or look-up tables when that applies).
Do not import .dwg files into the families. Instead, find out the dimensions of the object and model it in Revit.
If the size of the family exceeds 2 megabytes, consider a revision/clean up/purge/optimization of the family. (agreed)
Nesting families is necessary, but try not to have too many levels of nesting, and always purge the nested families.
For some cases, consider combining loadable families with system families such as curtain panels & curtain walls, or profiles & wall types.
Adaptive families should be used only for things that can't be done with generic families. If it can be done with generic, use generic.
Arrays should be made with nested families, not with local objects.
Eliminate unnecessary parameters, unnecessary constraints.
Simplify the geometry of the object, eliminating the small model elements that are not essential.
Do not use voids, if possible. (How do you model curves, holes, etc...? Switch to adaptive families for those types of objects)


For the architects and engineers out there the benefit of BIM should begin to bear fruit by now. If not, you might still be in the “Production Only” level of thinking. For the contractors and FM Directors out there, what this means is full accountability of all the smart objects in rooms, including the rooms themselves. Each object represents not only the real-world object, but all the attributes associated with them such as location, cost, warranty and power requirements to name a few.
A question I heard from some recently promoted BIM Managers is: Do I model EVERYTHING?


To Model or not to Model that is the question: Often times I come across MEP firms that ask, “Why should we do this in Revit, our process is just fine the way it is?” To which I ask, “How many projects do you have errors on because you didn’t coordinate routing?” All of them. The question isn’t why, but how to use Revit for engineering. Do you need to model every bell housing, strap brace and bolt? No, you don’t.


Any other suggestions out there?

[david_peterson]

For some of this it really depends on the item. Coming from the structural side, I've modeled just about everything. I was at one point modeling bent plate slab edges but that became a really pain in the butt and offered very little in the added bonus for me (the guy creating CD's). So I've gotten away from that a little bit. My latest theory for the structural world was model anything that we (the structural engineer of record) are responsible for that would ever get in anybodies way. So to that point, yes, model basically everything. Since adding rebar to Concrete is rather easy and makes that portion of the detailing easier, model it. For structures I can say this: Cast in place concrete is a pain in the butt to model, but easy to add bars to to detail, so model them. Steel is really easy to model, but harder to get your 3d model worth something when it comes to connections, so skip the plans, nuts and bolts. But again if it gets in anybodies way, model it.

On the Arch side, I'd tend to say, model what you can; remember that your model should be based off the design intent that you provide in your specs. If you are doing a performance based spec, but list an American Standard toilet, use that particular toilet. That manufacturer has them available, so yes, use them. What to include in that family? Simply provide a link to the website. Doesn't take up much space in the family and rather simple to do. Cabinets/casework is another area that really needs to be address. If you're going to place a cabinet in your model, make sure it exist and it isn't a custom unit (unless you really want to use custom units). Furniture is the big one that I see as a model killer. Most furniture families have way to much detail in them and therefore are very heavy. In most cases, we use a separate model for furniture since we really only use it for planning purposes as it's usually owner supplied.
At this point unless you're doing a IPD method, the "Design Models" are just that. They are there to show design intent. It's up to Mr. Contractor to provide a coordinated construction model. We allow them to use our model as a BOD, but take no responsibility for it. Our model is just a tool used to create PDFs and paper prints for our contract documents. The model isn't generally included yet. So for the contractor it's "use at your own risk".

At the end of the day, how you model and what you model and what LOD you use, it dependent on what the Owner is looking for and what the owner is paying for.
Will your project run much smoother in CA if you hand over a clash free LOD 500 model to your contractor? Yes. Are most owners willing to pay for that level of service? Not Yet.

Model what you need to model, and make sure what you model can be purchased and built. If you fail on either one of those, you will fail. Make sure the design intent of your routing makes sense and provides a viable solution. Should you as a design professional model the exact placement of every pipe hanger? My opinion is no. That's up do the the guys in the field to coordinate. Should you model support posts and hangers for water pipes say 12"dia and over? I'd say maybe to yes. You want to know where that hanger is being placed so you can provide enough support steel for it. But at the same time, you need to have a contractor that's willing to follow your plan and not change every aspect of it (I've had it happen before).
That's my 2 cents on what to model and what not to model.

[rbcameron1]

2 years later.

http://www.evolvebim.com/single-post/2017/01/17/Revit-Family-Anatomy---Part-02