Crash Course in Test Fitting

Table of Contents

Its About Solving the Deals


In this blog post I will attempt to give readers a crash-course in test fitting. We will use our software, TestFit (fitting name, no?) to show many of the concepts, along with some meaningful graphics to explain deal concepts. If you already know why we test fit, you can skip ahead to the TestFit crash course.

One side note: The audience for this post is students interested in using TestFit for coursework or real estate development competitions. Experienced architects and developers might not learn too much, other than the basics of our software.

Why do we do test fits? The answer lies in how complicated it is to create viable real estate deals. Real estate deals, in the mind of this author, boil down to five sub-problems:

  1. Design – How is the product designed?
  2. Capital – How is the deal structured? 
  3. Land – Where is the building, and shape of the land it is on?
  4. Construction – How will it be built, and what will it cost?
  5. Zoning – Does the design conform, or will it need additional entitlements?

Capital, Construction, and Zoning

Capital, construction, and zoning generally start out on a pretty solid set of facts: LPs and GPs want to achieve a solid YoC (normally 6.5%), GCs simply execute on construction documentation while meticulously keeping track of cost. Zoning is generally known, and operates under various land use controls like DU/AC, FAR, Height, and Lot (or building) coverage.

Some Definitions:

  • LPs: Limited Partners, often the equity component of a real estate deal
  • GPs: General Partners, who are normally referred to as “Developers” in the USA. 
  • GCs: General Contractors, the companies that get buildings constructed
  • YoC: The ratio of money made in the first 12 months to total cap ex
  • Cap Ex: Capital Expenditure, the money spent by companies on physical assets
  • FAR or Floor Area Ratio: the ratio of built floor area to the land it sits on (see image below)
  • Lot Coverage: the percentage of the lot covered by building
  • DU/AC: Dwelling units per acre
  • Acre: 43,560 square feet, or 1 Chain*1 Furlong (the area an ox team can plow in one go)
FAR: Floor Area Ratio - what is the total building area compared


Land is a pretty simple concept. It and its fixtures are static, unmoving, and permanent. The only asset class that is said to be “real” hence the term “real estate”. Land gets a bit complicated with assemblages, but in general its analysis is limited to who owns it now, what kind of soils are on it, what kind of zoning is attached to it, what kind of private covenants are associated with it (hello Houston), and how bad is its topography.

Some Definitions:

  • Assemblage: Putting together several parcels to make a new, more valuable parcel (see below)
  • Private Covenant: Zoning, but without government intervention (Some private covenants can and have been ruled unconstitutional, however)
  • Fixture: Anything attached to the land. If you have to hire someone to move or demolish it, its a fixture.
  • Topography: The slope of a site, and how extreme that slope is

Solving the Subjective Design Component

Now into the meat and potatoes of what we are best at here at TestFit Inc: Solving the spatial layout. The main problem with building design is that there are no “right” answers. The solution space is as large as the universe itself. At TestFit we simplify buildings down to component parts to constrain the solution space from infinity to only a few trillion possible solutions.

The Major Components of the Design of a Housing Deal

Depending upon the land, zoning, capital and construction, the makeup of the following list will change drastically on a percentage basis.
  • Dwelling units – housing for people and family
  • Parking facility – housing for cars (we build a lot of this in the US)
  • Human circulation – corridors, stairs, and lifts for getting to units
  • Car circulation – roads for moving cars around
  • Leasing and amenities – space to convince people to rent

The table below gives some comps between building types and their respective component percentages. In a world where a YoC of 6.5% is desired, increasing the area of units versus all other spaces becomes quite important. This is actually an industry metric: Building Efficiency. Building efficiency is most often used without the parking facility.

320 Units @ 875 SF Avg
Space TypeWrap DealPodium DealGarden Deal
Parking Facility30.7%29.6%29.2%
Stairs + Lifts1.6%1.8%0.9%
Leasing + Amenity1.0%1.0%1.1%

Some Definitions:

  • Wrap Deal: Parking facility is wrapped with housing units.
  • Podium Deal: The housing units sit atop the parking facility.
  • Garden Deal: The housing is individual buildings, surface parked.
  • Building Efficiency: The percentage of the building that is rentable.
Building Efficiency what is the total area compared to the usable or rentable area?

Using TestFit to Solve Deal Design

Now we transition to the more practical part of this blog post: how to use our software to solve deal design. TestFit supports some construction, capital, and zoning problems, but only at the highest level. It’s main focus is using algorithms to allocate net rentable area on a plan, and to create a vision for what a project could  be.
The following series of videos give an overview of how TestFit works. 

Working With Presets

The building types mentioned above are easily wielded within TestFit’s configurator by using our default presets. This ~9 minute video will give a good overview of those presets and building types. 

Working With Sites

Within TestFit we use sites to define the land area. Sites also have some other interesting properties, like setbacks. The following video will give an overview of sites.

Understand Density with Sites, Schemes, and Presets

The cross product of the last two videos is how sites (land) and (building design) presets work together to show what density is possible with different combinations of the two.

Using the Zoning and Building Inputs

Now that you have a handle on sites and presets, let’s take a look at zoning parameters and how to get into the weeds via building inputs.

These few tutorials are just the beginning on how to solve or even optimize real estate deals using TestFit. If you would like to learn more via tutorials, please check out our Knowledge Base. Not yet using TestFit? Sign up to try it now.

Concluding Remarks

I hope this post was informative on why we design different shapes and styles of buildings. With tools like TestFit, anyone can now site plan buildings. It is a democratization tool. That being said, it takes several years to fully understand the true nature of buildings, and for users to get an intuitive sense of how they should solve a deal–but it takes decades without technology to have that same sense.

5 ½ ways architects can show multifamily developers they get it

As an architect, how do you serve your clients’ needs more quickly?

Aka: how do you win more work? 

Developers are human too. Sometimes impatient. Often questioning your math. 

Hands up if you’ve ever heard one of these statements from the multifamily developers you work with:

“We’ve built our own, proprietary units. Please use the attached.”

“What’s your Efficiency? We don’t build under 83%”

“What’s the Mix, I want all the jr. 1Beds. They drive the highest $/SF.”

“We are cost conscious, why do I need so much Vertical Transport?”

“Well this plan is nice but now I need to run the numbers…” 

In this article, we’ll try to explain the developer’s point of view. And better yet, we’ll give you the tools (yes, in TestFit) to help answer their concerns. 

If you’re already familiar with TestFit, skip ahead to how you can answer these client questions.

Figure 1.0 - Multi-Family Master Planning with TestFit.

If you’re not familiar with TestFit, think of it as your power tool for rapid site planning & on-the-fly changes. This isn’t a generative design tool with optioneering; we call it your building configurator. 

The basic premise is we allow you to input constraints in the form of parameters to better shape a density study. But the world is yours in TestFit. You can constrain a site or building as much or as little as you’d like. Your site plan is automatically generated right on top of GIS data. We have co-creation tools built in as well to allow users truly craft their unique vision. 

Save your design time for the architectural details that set your firm apart; not redrawing empty boxes. And most important, learn how to speak to multifamily developers in their language.  

📢Back to our scheduled programming: answering these tricky questions from the multifamily developers you work with. 

1. The proof is in the proprietary units

Developer statement #1: “We’ve built our own, proprietary units. Please use the attached.” 

Translation: “They have standardized their costs based on unit prototypes.

You: “No problem, we can add unique units easily.”


Unique Units

Developers like standardization. It’s easier to budget and allows them to compare sites faster. TestFit now allows you to put in the unique units that your multifamily developer wants to see. 

The way we do this in TestFit is through Attachments. It lives at the top of the Unit Database menu in the configurator panel.

Fig 2.0 - Add unique units with TestFit’s Unique Unit Underlay.

By default, TestFit ships with a set of basic unit layouts for you to replace with your unique units. Click Editor and the unit you would like to edit. You’ll see the standard units in there. It’s a simple image upload to keep the program light and moving quickly. 

Here is where easy it is to upload your unique units! Be warned, there’s a long line of units. That’s by design. If your Developer has 30 unit prototypes, you and I both know that it won’t be efficient to use all of them in a single building. It’s easy for you to upload all of those units though on one image sheet and recalibrate your units based on the select few you need for your building. 

Pro-Tip: Flex on ‘em.

Some sites require wonky angles which are not conducive to standard units. So you’ve gotta add some flex parameters to the units. In the unit editor on the parameter panel (left side), you can add max linear and angular flex to allow the units to adjust to fit the angles. 

Learn more about our Unit Editor in our Knowledge Base

2. Net rentable floor area

Developer: “What’s your Net-Rentable Efficiency? We don’t build under 83%.”

Translation: “I want to maximize my net rentable square footage.”

You: “We do too! Let’s make tweaks to get there.” 

Well we don’t get out of bed for a fee less than 15% of the total project cost …just kidding! 

Efficiency is important. To be clear, we are talking about the efficiency of floor area in the form of Net Rentable Area. But it means more than just efficiently using the floor area. To developers, it directly relates to the efficient use of capital and operational costs. 

We’ve done quite a bit of research on Efficiency in multifamily. In fact, that’ll be a blog a post for another time, but in short, our key findings are:

1. Dead End Units are the most efficient way to end a corridor.

2. There is a regressive relationship between the number of intersections and a decrease in efficiency. 

Fig 3.0 - Number of 4-way intersections vs building efficiency

4. Wrap Products struggle to reach high levels of efficiency. 

5. The depth of units has a greater effect on efficiency at smaller numbers and becomes nominal after 30’-35’.

Fig 4.0 - Efficiency of building components vs unit depth.

6. Interior corners are a problem child – so much so, we wrote a whole blog on it.

There’s a lot to unpack here but hopefully these insights give you some good rules of thumb while test fitting.

We also have the Tabulation Dashboard, your live-updating best friend. On the bottom of the TestFit screen, you’ll see the Tabulation Dashboard. Here you can find all the data relating to the building you’ve been testfitting. Mo’ data, mo’ problems? Not so! Hit the “+ Expand Tabulation” icon to see the values that make up the dashboard, such as Gross Conditioned space, unit breakdowns, facade take offs, space sizes and more! Developers love their data, especially when it can be tracked to the smallest detail. 

The effect of an increased setback instantaneously affects all other outputs of the Deal Information Model.
Fig 5.0 TestFit's Development Panel allows you to easily compare units vs financials.

(If you’d like new blog posts delivered to your inbox, please fill out the field below. If you already are, we might have a question or two for you to make sure we’re only sending you content you care about.) If not, carry on for perfecting that unit mix.

3. Mix it up - The Unit Mix

Developer: “What’s the Mix? I want all the Jr. 1Beds. They drive the highest $/SF”

Translation: “I need to maximize my revenue here. Do you get that?”

You: “No problem, we can easily adjust that.”

*scrambles to TestFit’s Unit Mix Matrix*

Unit Mix Matrix

What we have here is an extremely powerful unit mix configurator that allows you to customize the unit mix to within a few percentage points. 

Fig 6.0 - TestFit’s Unit Mix Configurator allows you to optimize your unit mix for maximum $/SF.

Here you can adjust the weight of units you would like. For instance, the image above shows Studios at a target weight of 40% Studios, 30% -1 Beds, 15% – 2 Beds, and 15% – 3beds. Adjust any of those and you’ll see your building update in real time. You can pack in all the Jr. 1-Beds your developer wants. 

4. What's with all the Ups + Downs?

Developer: “We are quite cost conscious on this project, why do I need so much Vertical Transport?”

Translation: “Do we have a need for all the elevators and stairs?”

You: “Code, but let’s dive into why!

Unfortunate fact: fires happen. They are scary. You want your tenants to be able to get out – fast. Stairs are like wearing layers in Chicago; if you have them you can always take them off, but you will be freezing or in trouble if you don’t.

TestFit is parameter driven. A few of those parameters are directly linked to life safety codes. Our verticals menu, seen below, defaults to IBC code. We allow you to change these as you see fit. 

Figure 7.0 - Verticals menu in TestFit where you can change Vertical Transport Parameters.

Changes you can make to the Life Safety Parameters include:

  • Adjust the Vertical Transport to a per unit basis
  • Stairs – ya need ‘em, but can adjust based on units and dead end distances
  • Long corridors = Fire doors. TestFit places those for you. You can toggle them on and off on the top of the verticals menu.

In conversations with developers, you can now point to these constraints and give them the ability to request deviations from the code should they see fit. 

5. Deal or No Deal?

Developer – “Well this is nice but now I need to run the numbers…” 

Translation – “I want to see if this deal pencils before committing.”

You – *Deals Editor has entered the chat* 

Understanding and prequalifying a site for development is the bread and butter of your developers. They want to know where to deploy their capital effectively and while design is important, cost & revenue are more top of mind for them. TestFit’s Deals Editor allows you to show your developer you understand the importance of cost & revenue.

Deals Editor + Development Summary

The Deals Editor is typically the last parameter set you will adjust in the test fitting process. With our Deals Editor, you can input the base costs for the project such as land costs, soft costs per unit or cost per SF and more. The buckets for costs are at the top. What’s more: as you adjust the unit mix, the operational costs and income update live in the Development Summary.

Figure 8.0 - Deals Editor- Adjust revenue streams and costs to land at a Yield on Cost Estimate.

TestFit is the first example of a modern CAD tool embedding financial analytics. We’re pretty excited about it.

The Deals Editor is a fantastic tool to better frame conversations when evaluating a site with developers.  For instance, a developer may want to provide their assumed costs, targeted rents and proposed land value. This allows your design to hopefully fit into the yield on cost that the developer is targeting.

The deals tab really is your secret communication sauce to speak developer. It also:

  • cuts down on iterations you do
  • improves your back-and-forth communication time with developers 

Pro tip: If you select one site, you will see the deal metrics for just that site, but if you have multiple sites, select outside of them and you will see your deal metrics for the entire masterplan 💥

½ a conclusion

Maybe you’re not fluent in developer yet, but we hope this “Architect’s Guide to Multifamily Developers” has given you some insight into what they value. And tools to help you show that you get it. 

We are here for our architects. We want to enable y’all to win more work, faster, through smart design. TestFit removes the need for mundane tasks, like counting parking stalls, and enables you to refocus on the design.

With our world leading co-creation tools and power users like you, we aren’t just making space… we’re changing our industry. Who’s with us?

Working with Fill-Type Garages

Garage lined with housing units aka Donut Fill

What is a Fill-Type Garage?

Simply put? Fill a site with parking in an irregular fashion. TestFit handles three major fill-type garage scenarios with parking: The Podium Fill; The Donut; and The Donut + Wrap. Sounds pretty appetizing, right?

The Podium Fill

Fill the site with parking, put building on top of it. To achieve this, simply select “podium fill” on the preset panel.

podium fill parking in TestFit
Site with garage parking and building on top

The Texas Donut

Fill the entire site with parking, but line the garage with housing units. Affectionately called the “Texas Donut”. In TestFit, simply select “donut” on the presets panel.

Garage lined with housing units aka Donut Fill
parking surrounded by housing units in TestFit

The Filled Donut + Wrap

Sometimes a site has a weird shape, and the garage is used to regularize that shape. This is less easy to achieve in TestFit, but still achievable.

Step One: Select donut from the preset panel

Step Two: Slide a setback to shrink the garage footprint

Step Three: Set building wrap levels to 5

Step Four: “Explode” the model to manual mode

Step Five: Reset the setbacks

Step Six: Manually add building mass

Step Seven: Solve by toggling out of manual mode

Regularize an odd site shape with the garage and TestFit's Donut Fill

Here is a swift comparison, with two “Donut Fill + Wrap” options: