Whether you call them clearance zones, clearance areas, access areas, obstruction clearances, overhead clearances…whether you like to see them in red, blue, or patterned…whether you need to make sure that there’s enough room for something to be accessed, opened, ventilate properly, fit properly…modeling the required space around an object is a routine part of using Revit and working with Revit families.

 

Bakery retarder oven with clearances for door access and overhead obstruction

Bakery retarder oven with clearances for door access and overhead obstruction

I’m not going to explain anything about how clearances work in Revit, because you can simply google “Revit clearance zones” and find a whole handful of perfect tutorials on how to go about it. But what you’ll also notice is that not one of those tutorials comes from Autodesk themselves. And this despite Revit having an Interference Check tool, for which clearance zones would seem to be a key ingredient.

What I want to suggest is that, given how widely applicable they are, maybe it makes sense for Revit to treat clearances as more of a built-in or standard feature. While building design firms will always have different needs regarding what clearances need to be checked and how they want to see them, they will also always share the general need to model clearances. I think it’s fair enough that Autodesk don’t force any standard settings regarding how clearances are shown, but I think there’s a simple first step that would make a lot of sense: a built-in subcategory.

A more complex example of clearances for a rooftop air handling unit.

A more complex example of clearances for a rooftop air handling unit. This time with dashed outline instead of solid.

If you checked any of the tutorials linked above, you’ll find they all start with the same step of creating a new family subcategory for the clearance geometry. The problem with this approach is that you can easily end up with different subcategory names for the same thing. This happens either because content comes from different sources – a manufacturer, your firm and project partner, for example – or because the terminology used isn’t broad enough – someone adds an “access areas” subcategory to one family and that doesn’t seem accurate for an “overhead clearance” needed in another family, for example.

If Revit came with a built-in “Clearances” subcategory, at least for certain family categories that tend to need them, wouldn’t that save users a lot of repetitive setup, tedious tweaking and accidental oversights? I realize that having the same subcategory in different family categories would still require turning each on and off separately, and I would suggest that Revit also do something to correct that – not just for clearances but for any built-in subcategory that is shared across categories. It shouldn’t be a required setting (turning on/off for individual categories still seems valuable), but an option that’s available as needed.

A more unusual example of a clearance for opening the lid on a meat grinder.

Clearance for opening the lid on a meat grinder. A more unusual example but one that can be important for commercial kitchen layouts.

I’ve been working quite a bit with clearances recently, and there is more to say on the topic, but I think a built-in subcategory is an obvious place to start. Do you agree? Should “Clearances” be a part of all family categories or just certain ones? Do you have other ideas about how clearances should be handled in Revit? Perhaps something to discuss after-hours at this year’s Building Content Summit in July. For now, share your ideas by commenting on this post or tweeting them to @andekan.