ADU Feasibility Studies: A Valuable First Step

As you begin your accessory dwelling unit (ADU) build process, you will eventually encounter the phrase “feasibility study” or “feasibility report.” A complete Feasibility Study is an important first step that can help inform your decision of whether or not to build an ADU, plus where to locate it on your property given all of the relevant constraints & considerations.

What does “feasibility study” actually mean?

In short, a feasibility study or feasibility report determines how realistic an ADU build would be on your property and what it would cost to do so. A feasibility report assesses the viability of a project, then assigns a cost for actually doing the design and build. These studies are incredibly useful to avoid spending excessive money on a project that cannot be done in the first place, as well as getting a firm view of the cost of the entire project before moving forward. This initial assessment considers any potential roadblocks and other factors that will affect your build to ensure we have all the necessary information to accurately scope your project. The main purpose is to lock in on the total cost of your ADU build by examining the components first.

Is a feasibility study necessary?

Feasibility studies are not technically a required part of a build, and some architecture firms may move right to full design, while contractors may begin construction without a feasibility study. The problem is that this approach leaves the homeowner open to undue risk. As a design/build firm, we are accountable for the ultimate success of the project and are on the hook for actually building what we design.

Because of this, we find that the Feasibility Study is a crucial step in an ADU build, since they are designed to save time and money for the homeowner on the overall ADU project. Deciding to forego a full feasibility study will most likely lead to a lot of surprises later. SnapADU started requiring Feasibility as a first step in all projects to avoid unpleasant discoveries, such as a utility line running right through the path of the proposed ADU location, or an easement preventing the ADU from being built in the proposed location.

We want to ensure we can stand by the cost numbers we will provide for your build. The only way to do that is to ensure we have a clear view of the project requirements upfront.

How much does a Feasibility Study cost and what is included?

SnapADU includes a Feasibility Study as the first step of a design/build project, at a cost of $2500. This includes:

• Site Plan. Prepare a site plan placing the ADU on the property. Show the location of the primary residence and other existing structures, high-level topography and ancillary development like fences and walls. Lay out the desired ADU footprint to optimize use of space given setbacks, zoning requirements, and other relevant property constraints.
• Utility Mapping. Locate existing private utilities to understand potential interference with ADU location. Determine expected requirements for electrical panel, including engineering load calculations.
• Electrical Panel Calculations. Determine expected load requirements for electrical panel. Evaluate existing panel to determine if current capacity is sufficient or if an upgrade is needed.
• ADU Design. Finalize floor plan, elevations and electrical plan. For customized plans, include all altered design elements for approval.
• Feasibility Report. Incorporate all items noted above, as well as relevant property data, development standards & regulations on setbacks, height, and lot coverage ratios, plus any regulatory / legal constraints.
• Guaranteed Build Price. Deliver final Construction Estimate reflective of new information resulting from all items discovered during Feasibility.

What types of feasibility reports are there for an ADU?

There are a number of different types of feasibility studies that can be used to assess different aspects of your build:

ADU Feasibility Study

An ADU Feasibility Study examines all aspects of a basic ADU build on a flat lot, including the setback and zoning requirements, so that we can determine the buildable envelope for the ADU. As part of that, all existing utilities, such as sewer, water, gas and electric, are mapped out. This assessment helps us place your ADU in a location that will not require significant rerouting of utilities, and ideally, that avoids long utility runs to tie into the existing lines. A utility study also assesses the costs of installing, connecting, maintaining, or removing any of these utilities. Access is also assessed to ensure that we will be able to adequately get to the build site of the ADU with our equipment.

Sewer Study

Sewer studies, similar to those mentioned above, are not necessary in every case. This type of feasibility study is employed if you have an existing septic system in place on your property, but would like to connect to your city’s sewer system. Some cities may also mandate a video of the sewer lateral. Some homeowners choose to perform a sewer study if they suspect root damage or other problems with the existing lines.

Septic Study

A septic feasibility study accomplishes three things. First, it will map out your existing septic system so that we understand constraints presented; we cannot, for example, locate your ADU on top of leach lines. Second, this study would be used to plan a new septic system for the ADU if this is necessary. Third and finally, a septic study will give you budgeted costs for altering your existing system or designing & installing a new one.

Retaining Wall Study

Exactly how it sounds, a retaining wall feasibility study examines what kind of wall is necessary, plus determines the cost to put this wall into place. Retaining walls are not always necessary, so this study will not apply to every build project. You may also be able to consider different kinds of wall options, including a keystone wall, soil retention wall, or CMU wall.

Grading Study

If you are looking to build out your ADU on a hillside, a grading study will assess  what needs to be done to build your new structure. This includes observing how much dirt needs to be moved and how much it will cost to do so. In some cases when a lot of soil is to be moved, a grading plan may be required by the city. The threshold for the quantify of soil triggers the need for a grading plan; these thresholds vary by jurisdiction.

Right-of-Way Study

A right-of-way study is used if you are seeking to add a new access point to your property. A study is also needed if you do any work outside of your property boundaries (e.g. in “public property,” or the “public right-of-way”). For example, if your ADU will be in the back of your property and away from your driveway, you might look into adding a new road or back entrance to make it easier to access the structure. These studies tend to be a bit more complicated, as it is likely necessary to go to the city to discuss adding this new access point. However, these are all conversations your contractor will be happy to have with you.

How does a feasibility study affect my build?

Depending on the findings of your feasibility assessment, there is always the possibility a build will be determined impossible or too expensive. This is where the true value of these studies becomes obvious, as it saves the homeowner from investing significant time and money into a project that is later deemed unviable. It is a safeguard to ensure your money is not wasted or misused.

On the other hand, a more positive feasibility study will confirm the desired ADU can be built, and also offer a fixed price associated with the project. Once you have this budget, you can then determine if this build is a worthwhile investment for your personal goals.

What do I need to do to prepare for a feasibility study?

Short answer: nothing! Yet another reason why feasibilities are so valuable to an ADU project. The entire purpose of the study is to uncover anything that needs to be done to prepare or complete your build, so you get to sit back and let SnapADU do the work for you. We will fill you in along the way, to keep you well informed on the process and make sure you are involved in any key decision points.

Building an ADU is not always as simple as having an idea, putting together plans, and building a structure. There are often many more steps involved in bringing that idea to fruition and many of those steps can be quite costly. Feasibility studies provide a great safeguard of your money between the “idea” and “plans” stage, making them well worth the time and money. It is one of the most effective methods of making this complex process less complicated, less costly, and less intimidating.

Get started with your Project Assessment so we can take a look at your property.