According to Multifamily Executive, the Core & Shell typology, or Tower as they refer to it, is “invariably of Type-1 construction, meaning concrete and/or steel, and access depends exclusively on elevators, exit stairs, ventilation shafts, and other building services. Residential tower floor plates are generally smaller than those of office towers and can range from less than 8,000 square feet to 18,000 square feet or larger, with many in the 12,000- to 15,000-square-foot range. […]
Even when efficiently designed, the tower is among the most expensive residential building typologies to build. Given the tower’s cost, difficulties with entitlement, and the densities that can be obtained with the podium, it’s often advisable to do a comparative analysis between the two before proceeding.”
Let’s explore how to design a Core & Shell product in Giraffe with this easy step-by-step guide.
Consider Requirements and Assumptions
By the nature of the scale of typical Core & Shell construction, this typology is best reserved for high-density areas. Unlike Podium or Wrap projects, Core & Shell are more often majority office space or hospitality (hotel) than they are purely residential towers, although in some very dense cities the high-rise residential tower may be more common.
For high-rise towers, the allowable building envelope is often complex. Explore the frontage and setback requirements in your jurisdiction’s code. Understand the prescribed setbacks at various heights, as setbacks must usually step further as the building height rises. This may be determined by percentage or specific distance, depending on the jurisdiction.
💡 You may want to create an allowable envelope geometry to guide your design. Review Solving for Envelope and Set Back Requirements for assistance.
It is also helpful to visualize the zoning overlays and parcels on the map for context. Consider loading in Layers that demonstrate neighborhood information. Search your municipality’s open data resources to find applicable layers by Importing Non-Native Data Into Giraffe.
Giraffe has curated thousands of public data layers, and you can also add your own.
Giraffe connects the geometry you draw with the data you see through the concept of a Usage.
Giraffe comes with some default usages such as Residential , Road, Basement Carpark and Annotation , and you can create your own and copy them between projects.
Some suggested Usages for a Core & Shell building are:
Design the Building
By definition, the Core & Shell building typology is designed around central circulation that includes elevators, stair towers, and building amenities like public restrooms, storage, shafts, and mechanical.
Giraffe offers 3 methods of generating building geometry:
- Rectangle: Start with a 90° rectangular shape. Great for regularly shaped geometry.
- Spine: Start with a single line. Great for long buildings or L- and U-shaped geometry.
- Irregular Shapes: Start with existing geometry and edit using the standard toolset, or start with a generic polygon and apply a usage later.
💡 For precise distances, type a number on the keyboard, and hit enter. Learn more about Drawing Accurately
Drawing Around the Core
Giraffe geometry is solid. The Core & Shell typology is often a “doughnut” with a usage surrounding the core. To accomplish this with Giraffe, simply divide the floor plate in two around the core. You can divide this however it makes sense for your project.
💡 Review the Mixed Purpose Floors guide for more helpful tips.
Analyze for Success
There are two ways to analyze your project. Use the Urban Tab for high-level metrics, like FAR, GFA, and more. Use Analytics to build out a custom proforma that matches your assumptions with geometric data from the project to forecast performance.
Check for Jobs and Tax Impact on Community
It is important for the existing community that any new development, especially one of mixed-use, will add to the neighborhood. Demonstrate your understanding and care for these needs by analyzing the impact using Analytics .
💡 You may choose to start with the Zoning Analytics template if your main goal is to analyze for impact.
Some Measures you can add to analytics to solve for impact:
- Total Output: Value of dollars put back into the economy
- Multiply Dwelling Total Residents by the assumed average spend per person for your area.
- Total Employment: Number of Jobs created
- Update the Jobs per Area properties for the applicable Usages. IE, if you will have on-site staff, parking attendants, pool lifeguards, or dedicated property managers and leasing agents.
- Total Earnings: Compensation paid to employees
- Multiply the annual compensation by the Jobs per Gross Area for applicable usages.
- Taxes generated per dwelling or sqft
- If it is a for-sale product, calculate the property taxes per unit based on your current tax assessment assumptions
- If for rent, calculate the taxes you expect to pay annually and add as a Constant
Check for Profitability
The goal of most development projects in the private sector are to generate profit for the developer. Your own internal calculations for IRR or other return metrics can easily be built out in Analytics. If you need help, please schedule time with our customer success team and we can get you started!
💡 You may choose to start with the Build for Rent or Build for Sale Analytics templates if your main goal is to solve for profitability.
Some measures you may want to include:
- Hard Costs of both the Podium and the Wood-Frame structure
- Soft Costs
- Land Cost
- Net Potential Rent for residences and retail/commercial spaces
- Vacancy Rate
- Carrying Costs and other Financing
You can be as general or as granular as you need to be to feel confident with your project. Once you build out the perfect Analytics schema, save it to your workspace’s Templates library to use again and again.
Solve for Core Ratio
An important indicator for the profitability of a Core & Shell development is the percentage of core circulation vs the total floor space. As noted by Multifamily Executive, “The fight to achieve maximum efficiency is a major economic factor in tower design. In the most cost-effective towers, elevators, corridors, and exit stairs take up no more than 20% of the floor plate, leaving at least 80% as rentable square footage, which can be difficult to achieve.” Let’s set up a ratio measure in analytics to help you ensure your core is not too large.
Calculate the Core Area
- Create a new measure.
- Select sqft/sqm for the unit
- Select your Core usage from “Apply to features with this usage.” In this example, we used “Community” for the core.
- Select the “Gross Area” property for the component
- Type “A” into the formula box
Calculate the Percent of Core Area to Total Building Area
- Create a new measure
- Select “percent” as the unit
- Add a subtotal of “Square Feet (or meters) in Built Form as component A
- Add the Core Area measure as component B
- Use this formula in the formula box to calculate the percentage: (B/A)*100
Winters, Patrick, AIA. 2016. “Designing Density in Today’s Urban Environments.” Multifamily Executive. September 9, 2016. https://www.multifamilyexecutive.com/design-development/designing-density-in-todays-urban-environments_o.