Sketching Massing Alternatives in Three Dimensions

This exercise explores techniques for translating the massing regulations provided in a zoning regulation into three-dimensional building envelopes and specific massing alternatives. Massing regulations are one way that cities regulate the character of neighborhoods. By specifying the unbuildable margins of property parcels, known as setbacks, and maximum height limits, each parcel has a unique three-dimensional potential zoning envelope that defines the extent the extent of the buildable area above each parcel. The zoning ordinance also typically specifies a maximum ratio of the useable floor area of a development to the area of the development's parcel, floor to area ratio or FAR. There are often several potential massing alternatives that might be specified to fit a building of a certain FAR into potential zoning envelope. This exercise provides some techniques for visualizing and presenting the regulatory envelopes and potential development scenarios for a neighborhood in Boston's North End.

Google Sketchup Basics

This tutorial will introduce a very simple, yet powerful 3d modeling tool, Sketchup. This project will introduce the most basic drawing techniques and model organization concepts. Rather than going deep into each step in this text, we will provide references to the Google Sketchup Help and videos, referenced below. The Video tutorials are very goos. They include Audio, so plug in your headphones, or you will be missing a lot! Wherever more detailed technical information about a tool may be required, we will refer to applicable documentation in Sketchup's on-line help, with references highligted like this.

• The first 12 Video Tutorials
• Make a New Layer
• Draw Tool
• Value Control Box
• Using INferences
• Creating a Group
• The Outliner WIndow
• Push Pull Tool
• Texture-Mapping Images to Objects
• Using Projected Textures
• Use the Rotate Tool
• Use the Move Tool

The importance of Learning to Navigate in Sketchup

The key to success in any editing tool is to feel comfortable with placing your cursor in a specific location and creating and moving geometry exactly where you want it. Naturally, if you don;t get to this level of comfort, you will not have fun with modeling in sketchup. The interface is probably the most intuitive of all 3d editing interfaces, yet people aren;t born with an understanding of sketchup. This is why you should go through the first six of the short video tutorials referenced above.

Understanding how to Organize Your Work in Sketchup

Simply making shapes in sketchup is fairly easy, but after your model has more than a few shapes in it, you will find that it can be very difficult to understand what shapes you are selecting and editing. A good model may have different alternatives in it that share a context, but that you may want to selectively turn on and off. Without understanding how to use Layers and the object Outliner to organize your model, you will get very confused and frustrated by sketchup.

The Boston Zoning Ordinance

We are intested in exploring the potential alternative massing scenarios for some parcels near the Paul Revere Mall in Boston's North End. To begin, we will find the apropriate articles of The Boston Zoning Ordinance. In particular, in particular, we are interested in the map that covers the North end Neighborhood District Which tells us that our parcels are in the MFR zone. Then we need the applicable dimensional requirements for this zone, which are found in Article 54 of the zoning ordinance in Table C, which is near the end of the article.

Table C specifies the dimensional requirements as follows:

• Building Height Maximum: 55 feet
• Floor Area Ratio: 3.0
• Front Yard Minimum Depth: None
• Rear Yard Minimum Depth: 12 feet
• Side Yard Minimum Width: None

Lot Dimensions

The next step in determining the building potential for the lots in question is to figure out the exact dimensions of our parcel. For this, we have an image of the parcel boundaries with a graphic scale. In this case the image came from the cities GIS, but it could have just as easily have come from any scaled map that we may have scanned. You can download the North End parcel image by right-click this link and "Save Target As". It will be helpful if you create a new directory in the C:\temp folder to hold your work for this project.

First we bring the zoning map into sketchup, and scale it to real-world dimensions. For future reference we sketch in the fountain from the aerial photo. We can now sketch in the building lot and get its dimensions and area. Subtracting backyard setback yields the dimensions and area of the buildable area. The buildable envelope is an extrusion of the buildable area to the allowable height limit.

We will use Sketchup to begin exploring the dimensions of the parcel and the lot above it.

Create a Parcel

The first step in understanding the massing opportunities on a parcel is to learn what the total land area is for that parcel. Creating a parcel using sketchup will give us the opportunity to learn how to use the basic drawing tools, including the Draw Tool and Inferences amd . The parcel we will be studying is the one that is right under the "Ti" in Tilleston Street.

Organizing the Model

Lets take a look at how our parcel is represented in sketshup. We can use the select tool to select and get info on each of the edges of the parcel, and also the face that is created inside. Faces and Edges are the most basic types of objects in Sketchup. The entity Info window tells us that these are all on Layer0. This is the way it should be. until you are very comfortable in sketchup, All faces and edges that you draw should always be on layer0. But since the edges and the faces make up a higher-order object -- a parcel -- it will be useful if we can group it and give it a name. Then we will make a new layer for Parcels and move our parcel into that layer. Groups help us to organize our model into hierarchies of objects -- so we don't have to worry about every single line and face. Layers allow us to organize the model into thematic categories that can be turned on and off. It is very important to learn how to use groups and layers. They will allow us to control what we are selecting and editing even after our model becomes very complicated.

Punching the radio button next to a leyer makes it the Active Layer. The active layer is where the objects you draw will be placed. It is possible to place primitive objects in any layer you want, and then to group them and to put these groups in other layers. This capability is useful in some situations, but more often than not can cause a lot of serious 'confusion, as you will find that turning layers on and off will cause odd pieces of youre model to dissapear seemingly at random. If you find this happening, you should go inside of the group in question and select all of the primitive objects and move them to layer zero. To avoid this confusion ALWAYS LEAVE LAYER ZERO AS YOUR ACTIVE LAYER!

Start a Spreadsheet

In our real project, we will have several parcels to keep track of. We should start a spreadsheet to help us track the dimensional allowances of the parcels that the resulting GFA. Currently, we would have a line in this sheet for Parcel A that provides the land area of the parcel (722 square feet). We should have another cell that provides the Floor Area Ratio. THen we can create a calculated field that calculates the Total Gross Floor Area for this parcel as a function GFA = Parcel Area * FAR. SO the GFA that we would be permitted to build "As of Right" by the zoning would be 2166 square feet.

Create the Potential Building Floor Plate

The allowable building footprint is determined in our case by the edges of the parcel minus the reqired backyard setback, (12 feet). The Floor Plate will be a new polygon that represents the area of the parcel that can be built on. In this case, it covers the the entire parcel minus a 12 foot strip at the back. We will be happy that our parcel is grouped. By working outside the context of Parcel A group, we can draw the new footprint on top of it without dividing the parcel. The Tape Measure Tool will help us create a Construction Line that provides a guide that is parallel to the rear lot line.

The area of the buildable footprint of tha parcel could be called our potential floorplate. THis area is 494 Square Feet. We can enter this into the spreadsheet in a column named Floor Plate

Establish the Potential Zoning Envelope

The zoning ordinance specifies the maximum building height for this particular part of the city. This information, combined with the building footprint, tells us the potential buildable envelope. We can easily visualize this in Sketchup by extruding our floor plate polygon.

Developing a potential Massing Proposal

There are many possible configurations of building massing that would allow us to build the allowable Gross Floor Area within the allowable building envelope. We will explore a couple of these and eveluate them using sections and shadow studies. To draw the building we will turn off the Envelopes Layer to keep it out of the way. The footprint of our building does not necessarily have to cover the entire bottom of the zoning envelope. We may decide to create a smaller footprint and have a larger back yard. But our first massing scenario will be to explore the shortest possible building that creates the desired ampount of floor area. This scheme will build to the edge of the parcel and backyard setback.

We know the area of the parcel is 722 sqaure feet. our Floor Area to Lot Area ratio is 3.0. This means that our building may have 2066 square feet of useable floor space. If we use the maximum building footprint (494 sq ft) as the basis for our floors, then (dividing the total GFA by the square feet for the mazimum floor plate)we have one potential massing scenario would have 4.2 floors in a perfectly rectangular building that occupies the whole floor plate.

The simplest buildout scenario creates a simple four story building Or we can use more of our envelope with a five story building Now we can compare the effect of shadows of the four story scenario with shadows of the five story scenario (October 3 at 3:00 pm.)

Of course, there is always more than one way to do it. Rather than making all of our floors have the same footprint, we can make a building that has the same floor area but is taller, by adding terraces. This may also allow for a less imposing appearance fromthe park. For example, we may have 2 floors at 494 sq feet, and two floors of 400 sq feet apiece, and cap it off with a penthouse of 278 sq feet. This scenario will take more advantage of the height envelope, and will provide some nice outdoor areas for residents of the building. But what will be the shadow impacts on the park relative to our more compact scenario?

It is useful to be able to store alternative scenarios in our model. This is where the Outliner Window comes in. Currently our building is made of five individual groups. We can select all of these, and group them. We now have a group of groups! To be able to aggregate geometry like this is very handy, as we will see. Sketchup provides an Outliner Window that lets us explore and manege the model according to the hierachal organization. It is very useful to learn to do this, since sometimes you want to be able to isolate and sel;ect parts of the model that may be difficult to get to inside other objects. The outliner tool also lets us name, and make copies of groups, and to hide some and show others. We will demonstrate this by making an ltyernative copy of our building to play with, while hiding the original one.

You now can edit Building Scheme B and move the penthouse to the fromt of the building or the rear. Henceforth you can determine which building scheme is vidible in your model using the outline r window. It is worth noting that both buildings are on the Layer named Buildings. So that no matter which scheme we are looking at, we can control the look of the model, thematically by adjusting the visibility of layers.

Adding People and Cars

Our building fronts on a narrow street and has a park in the rear. A critical aspect of massing is how the building either stands over, or steps back from its surroundings. TO make this more clear, we can add soem items to the model for scale. Sketchup makes this very easy. The Components Window has many little models that we can easily drag into the model. There are vast libraries of this 3d-clip-art that we can download from the sketchup site. Using these components will give ua an opportunity to learn how to use the Rotate Tool.

Yes the streets inthe north end are very narrow, and they feel cozy because of the tall buildings built right to the sidewalk. This is part of tha character of the neighborhood.

Sections

It is useful when discussing the dimensions of a building and the spaces around them, to create a section diagram, which reduces the massing to a 2-dimensional diagram that we can add dimensions to. This way we can also show, cars and people standing in the vicinity of the building to get an idea of how the building may open up or close off the sky and create a streetscape of one character or another. To learn how to use sections in sketchup, I recommend that you look at the Sections video at the bottom of the beginning sketchup videos page.

Shadow Study Animations

By setting pages in the Skethup View->Tourguide options, we may save particular shadow settings. Then, exporting an animation will morph our shadows from one season or time to the next. These anaimations can be exported as avi files:

• 5 Story Scenario, 2:00 January to December
• 4 Story Scenario, 2:00 January to December