Looking at Evanston: Design Thoughts | Design of an ADU

Although Accessory Dwelling Units (ADUs) play a valuable role in the community as a whole, they ultimately exist to provide people with healthy and safe housing. This article focuses on the latter of these two goals – how to design ADUs that best meet the needs of our residents. As the final article in a two-part series on ADUs, this essay aims to give the people of Evanston a fuller understanding of why and how you or your neighbor would undertake an ADU project.

Like any project, your ADU should start with a goal. Why is it built and for whom is it built? In many cases, ADUs are used in multiple ways over time. They can function as an apartment for a renter or family member for years, to become a home-based business during a career transition, as in this recent roundtable article on a bicycle repair shop based in a garage. It helps to have a clear understanding of both the primary and initial purpose of the framework as well as the use cases sought over time, as this greatly affects the type of ADU that is best for you.

Then it can save time and money to come up with a budget range for an ADU project early on. Otherwise, you risk designing a unit that doesn’t fit your budget, which may require a redesign. While it’s tempting to search the internet for “dollar cost per square foot of an ADU”, it can often be difficult to compare apples to apples. Different types of ADUs typically have different cost ranges, and expenses such as utility hookups or permit fees can sometimes be excluded from an estimate.

(Copyright © AARP 2021, 2nd edition)

To get a first idea of ​​ADU costs, AARP’s “ABC’s of ADUs” cites construction costs under images of various ADUs in the guide. If you are a homeowner, it may be helpful to speak with the mortgagee of your primary home or with a trusted financial advisor to understand your financing options. This step ensures that residents design a project that not only meets their basic needs, but that they can eventually afford to build.

Once you have a coherent idea of ​​the project objective and the budget range, it may be a good time to focus on the ADU type.

While most people usually think of the freestanding “detached” ADU in a backyard, ADUs can also be part of the existing primary residence. They can be “interior” (for example, a conversion of an existing space in the house) or an extension of the main house. Finally, as is popular in Los Angeles, they can even be a garage conversion. Each of these options has pros and cons, which are explained in more granular detail in the city’s publication Evanston’s Guide to Accessory Dwelling Units.

Evanston’s Guide to Secondary Suites is a useful resource for residents wishing to undertake an ADU project. It is available on the Town of Evanston and Evanston Development Co-operative websites.

During the architectural design process, compliance with Evanston’s zoning and building codes will affect the design of your project. Fortunately, Evanston has a relatively flexible ADU code. Your “zoning district” is the primary variable in this equation. Anyone can find a property’s zoning district on Evanston 311 About My Place. A zoning district affects several things, including the allowable amounts of “building land cover” and “impervious surface cover” on your property.

While “Building Land Cover” determines the proportion of the property that can be occupied by buildings (as opposed to vacant land), “Impervious Surface Cover” regulates the percentage of hard surfaces (e.g. roofs, concrete driveways, etc.) that may occupy a property. Together, building land cover and impervious surface cover will be two of the main zoning policies that will determine the shape and size of your ADU. Regardless of your zoning district, however, new ADUs can only have 1,000 square feet of living space.

Three other zoning issues that need to be considered are setbacks, height and parking. Setbacks refer to the distance an ADU can be from a property lot line or principal residence, and requirements vary by structure type and zoning district. As for the height, one can go up to 28 feet with a pitched roof, providing flexibility in design. Finally, there is no need to add additional off-street parking space when building an ADU in Evanston, which opens up design options, but you cannot permanently reduce parking spaces. . If you remove any of your existing off-street parking spaces during an ADU project, upon completion of the project, you must have the same number of off-street parking spaces on the property.

Finally, two particular issues deserve special attention when designing the ADU: accessibility and durability. According to a study by Harvard University’s Joint Center for Housing Studies, only 1% of today’s housing stock contains all of the key features required for accessible living. If building an ADU for aging parents or a parent with a disability, it may be important to think about accessibility from the start. Given Evanston’s relatively lax off-street parking regulations, it is often possible to design an ADU at ground level. In addition, one can provide wider entrances and corridors without steps; future-proof designs in bathrooms; and accessible light switches and outlets, to name a few.

(© 2016 by Harvard College President and Scholars)

With the need for climate action on the rise, the new ADUs are also a great opportunity for more climate-resilient buildings. These structures can be fully electric without relying on natural gas. Integrating high-efficiency appliances can save energy and money. For example, an induction hob, an electric oven, an air source heat pump for space heating and cooling, a heat pump water heater for hot water, as well as a pump dryer heat can all contribute to a net zero potential. carbon building.

Structural insulated panels, pictured here at an Evanston Development Co-op job site in Evanston, can be a way to align an ADU project with climate action goals. (Kirk Wooller/Evanston Development Cooperative)

Additionally, an ADU can be very airtight and very energy efficient, keeping heating and cooling within the sealed building envelope. Combined with an energy recovery ventilator that continuously replaces stale indoor air with fresh outdoor air while maintaining air temperature, an ADU can efficiently provide clean, healthy air with less energy consumption. minimum. Plus, it can be relatively inexpensive to add electric vehicle charging to a garage or carport.

ADUs are exciting because in a relatively small space there is an abundance of design opportunities for a future home – a conversion of an underused part of a house, a garage or new space in a backyard. .

Regardless of their purpose, ADUs require a time commitment for site analysis, architectural design, construction drawings, permit review, and construction. Nevertheless, if the final structure matches the owner’s vision and needs, it is ideally worth it. Best of all, it’s one more accommodation in a city with limited supply and hopefully a welcome addition to the neighborhood.

Design Evanston’s “Eye on Evanston” articles focus on Evanston’s design history and make the case for good design. Visit designevanston.org to learn more about the organization.

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