Zoning Clearance Thoughts

A long time fellow Revit traveler reached out to me via Revit Lifeline last night asking about zoning clearance ideas. Where he lives and works they want designers to demonstrate the building is not too tall. They also want them to prove it doesn't extend into a zone that leans back into the site. All in all the code reduces the size of the building that can be built on any given property that falls under its jurisdiction.

I have heard and read about this concern many times over the years. But in response last night, I mocked up a quick example to see if it met his needs (waiting to hear back). I thought, "Blog post? I just posted something the other day...don't get carried away. Yeah, but you've only posted like twice this year slacker! So a blog post it is then..."

Here's a few images to ponder first. Pretty fancy house design eh? Doors and windows are so last century. I CAN design YOUR next home, just call when you're ready...operators are standing by.

The upper surface is a thin floor which is manipulated through Dynamo and Shape Editing. Lauren Schmidt's LandArchBIM blog is a very nice source for land techniques and I stole her graph ideas in this post to make it. Her post explains the technique relies on a sub-region to match whatever hardscape shape (property boundary in this case) is necessary. I used the floor's offset parameter to move it up above the surface by the zoning height required.

The front and back property boundary clearance requirement is built with a railing and profile. The fact that railings can be hosted by toposurface now opens this door wide. The surface form might not lend itself to a nice clean railing though, mileage will vary. You can see the rear railing is a little deformed in a couple spots. I built parameters into the profile so I could (using types) vary the height of the angle portion, change the angle, change the height above property (spring point of the lean) and the thickness of the railing.

I created a specific material to assign to it all so it can be mostly transparent.

My example is admittedly simplistic. How many property boundaries are really a simple rectangle? Pretty rare, about as rare as a purple unicorn that uses Revit? A front or rear boundary that has arcs and many segments will probably pose some issues creating a hosted railing. I can imagine things going wrong but I'll wait until I'm dealing with something specific to worry about that.

The file I mocked this up is in Revit 2020.2 and the dynamo graph (link has both RVT and Graph) is so simple that this screen shot would help you build it nearly a fast as downloading and opening it up. That's what I did with Lauren's example. You do need the packages I've circled.

Oh, the mockup has a massing element too, you'll have to turn massing on though. At first I thought I'd sweep a profile along the property edge defined by the upper surface. After I did that I thought of the railing. The learning curve is much less steep for a railing than massing, bonus being much faster too.

Decided to add a couple more images. I realized that I could have turned off the sub-category Interior Edges for Floors to hide the tessellation in the other images. It also occurred to me that another railing and profile configuration could deal with the top. I just created another type from my existing profile family to make it a 90 degree railing. A separate wide profile without a vertical portion would provide just a top surface. The floor and railing approach don't result in the same surfaces but within reason? If reason can be applied to a zoning requirement?

Here's both visible...

Property Lines without Digital Reference

As a follow up to a related post last week this post describes how we can create a property line when we lack any digital data to use. The survey may be an old hand drawn document provided as part of the deed or it could just be a printed drawing that nobody can find the file for. While we wait for a new survey we can still start with what we have. We've captured some bearing and distance information from my old survey drawing.

When we have a CAD file we can import as a resource the Property Line tool option: Create by Sketching makes it pretty easy. Since that's not an option in this situation we need to choose the other option: Create by entering distances and bearing.

Take a moment to revise the project units so they show the same units as the survey data. It helps to confirm the values we see in the dialog match those we've entered (it's shown that way in the image, not in the video). When we enter values for bearing a space between Degrees, Minutes and Seconds is all that's needed. To advance from one field to another we can use the TAB key to move forward or SHIFT + TAB to move backward in the dialog.

Also note that if the distance and bearing information is accurate enough Revit will report "closed". If the data isn't then it won't be able to report "closed" or show the area of the property. Unlike many sketch based elements Revit will tolerate a Property Line boundary that does not close. I altered the distance for the last segment to show the following error message that appears.

Once the Property Line is completed, click OK and we'll find the element is "stuck" to our cursor expecting us to decide where to place it. We pick an arbitrary spot and then move it so a corner of the Property Line is at a corner of the building. The goal is to make it easy to use Rotate True North and define the angle between the current Project North position of the building and the side of the property we'd like it to line up with.

In this example we've decided that the side of the house needs to be parallel to the East property boundary segment. Now we can use Rotate True North. When the tool starts we need to choose where the Rotation origin should go. In this case we need it to be at the corner of the building, the same corner where the corner of the Property Line is now. The first pick is rotation origin, the second pick is on the building and third pick is on the property line segment.

The task is much easier when we put the Property Line right on top of the building as a frame of reference. It also allows us to define the angle without trying to determine what it actually is.

Now that the orientation is correct we can move the Property Line into the correct location/position. Adding dimensions makes it easier to be accurate. We need to double check the values to make sure the changes to one dimensional direction don't alter other dimensions inappropriately.

This is a video demonstration of the concepts with captions, no audio.

Property and Setback Boundaries

I wrote a couple posts before about documenting these. The first was about using the property line tool to create the setback lines too. I used Override Elements in View to make the line pattern different. The second was dealing with the notion of 3D representation of these boundaries. Have a look if you are seeking ideas for these site and property documentation issues.

Property Boundaries and Setbacks

Massing a Property Boundary

Massing a Property Boundary

I read a thread at RevitForum.org last week that asked about seeing a property boundary in section views. Property Lines in Revit are just 2D so they don't show up, thus the question. It occurred to me as I read it that massing might fit the bill.

I started with a property boundary using the Property Line tool since it works nicely for that purpose otherwise. I used that as the "control" for the massing form.

Using an in-place mass family I sketched around the property boundary and used a parameter to manage an "offset", just in case I need to push/pull the massing edge. After I created a form from the sketch I did the same to control the top sketch with a separate parameter so I could potentially push/pull it too.

Now this will appear in a section view.

Taken a step further I added a void to remove the portion of the property mass that is "buildable" according to setback parameters. The design had better fit inside that "hole"!

Here's what the Parameters I used are.

I used a Massing sub-category to manage what the massing looked like, line pattern and color, so it would be easier to distinguish as a property boundary...hopefully.

Property and Setback Boundaries - The Property Line Tool

I wrote this article in October 2005. I was surprised it was so long ago. The file I used was old enough that it warned me, while upgrading, about the big changes to the room element, that came with Revit 9.0. This time I made a short video and you can listen and watch here if you prefer.

DWG Import - Lines Nearly Vertical/Horizontal are Changed

Revit alters the lines in a imported cad file if they are very nearly horizontal or vertical. It has done this for quite some time. It isn't clear if it isn't a problem very often or if it isn't noticed very often. I'm reminded of this issue by a recent post at AUGI naturally.

In this instance a member wrote that a property line (in a cad import) whose bearing is 89 degrees 57 minutes and 56 seconds is altered by Revit to simply 90 degrees even. The cad file isn't "changed" but what we see of it in Revit is.

If you use Revit's Property Line tool and opt for the Table of Distances and Bearings method you'll find you can create a property boundary that is faithful to the documented bearing data.


And the dialog itself with the resulting property line.


Aah...Trust...a database or cad file is only as reliable as we believe we can trust it to be. Once upon a time people trusted that the earth was flat. That proved to be false, I think. I haven't been in space myself so I have to trust that the astronauts and scientists who say they have been are telling me the truth. Now I know that the moon is round but I don't know that it is in fact a globe because I've never seen the "back" of it. I've never seen it spinning. My life experience and acquired knowledge tells me it is a globe but assumption and belief doesn't prove it. Anyone who enjoys Robert Heinlein's books would recognize that last little bit.

Importing cad files and "seeing" nothing to cause us to doubt the accuracy of the import permits us to work with the belief that everything is fine, trustworthy. But when we discover an inaccuracy regardless how meaningful or meaningless the issue really is it places doubt in our minds. This doubt is usually worse than the actual problem we've found.

As we transition from 2D methods to 3D methods and embrace the promise of Building Information Modeling (BIM) we need to be able to trust the data. This is much bigger than just software. It has to do with each person that comes into contact with the data, the model. Our contact must be done with this issue of trust in mind so that we don't invite doubt. When doubt exists our work must stand up under close scrutiny.