16 Biggest ADU Mistakes in 2021

Mar 20, 2021 | ADU

Even if you have gone through construction before, developing an ADU is very different from home remodeling or home addition. It is a challenging process! Instead, building an ADU is very much like developing a new home but on a smaller scale.

One of the hardest parts about building one is discovering that you have made a mistake during the process. Often, this leads to owners being forced to live with the consequences or spend additional dollars to remedy the problem.

We don’t want that to happen to you, so we’re going to look at some of the most common mistakes people make when developing an ADU and how to avoid them.



  1. Not Completing Proper ADU Research
  2. Skipping ADU Feasibility Study/Research
  3. Starting An ADU Without Budget
  4. Not Assembling Your ADU Team from the Start
  5. Hiring An ADU Contractor/Builder First
  6. Choosing ADU Professionals Based on Cost Only
  7. Trying to Use Premade ADU Plan
  8. Not Spending Sufficient Time in the ADU Design Process
  9. Poor Overall ADU Planning
  10. Not Planning for Enough ADU Storage
  11. Not Having An ADU Laundry Area
  12. Second Guessing Yourself at Every Turn
  13. Overspending on An ADU Conversion
  14. Not Comparing ADU Construction Estimates
  15. Homeowners Giving Direction to Subcontractors
  16. Not Leaving Money for Contingency


Not Completing Proper ADU Research

Developing an ADU is the second biggest investment most people will complete. Purchasing a house is the first.

When you purchase a house, you will:

• Complete research
• Educate yourself
• Work with a realtor
• Visit a few homes for sale
• Do your due diligence on the one you are about to purchase
• Execute on purchase

When you are about to develop an ADU, you should go through the same process. Do your research and find the right professionals. Then do your due diligence on the right type of ADU for you before executing. Here is the ADU Guidebook and eCourse which are a great resource of information about everything related to ADU research and development process.


Skipping ADU Feasibility Study/Research

ADU Feasibility research is imperative. If you skip this step, you could end up investing time and money into designs and plans that are not usable.

To avoid this, you should consult with design/planning professionals, not contractors, to understand the basic current local guidelines associated with feasibility. In some cases, you may even need to invest in a feasibility study which includes creating a site map and a potential meeting with your local planning department for clarifications.

Laws Associated with Feasibility

When researching feasibility, you need to pay attention to both ADU state and local laws.

State laws are more general and often used as a broader guideline. However, most local councils have adopted supplemental laws, requirements, and guidelines for building and planning that are specific to your area.

It is important to pay close attention to your local laws because properties on the same street may fall under different guidelines due to property:

• Condition
• Location
• Situation

Just because your neighbor was able to build an ADU one way does not mean you will be able to as well.

Important Parameters to Consider

There are multiple parameters to feasibility that you need to take into account when designing your ADU. A few important ones to look into are:

• Height limitations
• Occupancy rules
• Parking requirements
• Setback requirements

These are just a few you need to be aware of before starting your designing process. Due to this, it is often best to consult a designing professional to ensure you do not waste your time investing in an ADU design that is not feasible.


Starting An ADU Without Budget

Too often, we see homeowners who do not set a budget when they start their process. This is a big mistake.

Setting an ADU budget should always be one of the first steps for any development project. It should cover all costs associated with the ADU development including:

• Design
• Planning
• Engineering
• City fees
• Construction labor
• Finished materials
• Rough materials
• Special inspections fees

Each of these aspects needs to be broken down into the necessary items and types of professionals needed to create a complete detailed budget.

Why Your Budget Is Important

You don’t want to commit to a project and realize you can’t afford it. Hence, why budgeting from the start helps you determine what type of ADU will work best for you.

Having a budget also helps to prevent you from acquiring unnecessary costs. Essentially, with a budget, you can develop an ADU without overspending.


Not Assembling Your ADU Team from the Start

Always assemble your ADU team from the start. This includes the:

• Designer
• Engineer
• Builder

Having a fully assembled team from the start will help you with budgeting since you will know their costs upfront. It will also help avoid any setbacks that can occur when new team members bring new ideas to an already started design process. In a process where time is money, this can cost you.


Hiring An ADU Contractor/Builder First

While attempting to make the process easier on themselves, some homeowners will hire an ADU contractor first that budgets their project without actual designs, plans, or engineering in place.

By doing this, they are relying on the contractor’s blind estimates and allowing them to issue the necessary plans using his/her resources. Thus, they provide the contractor with full control of the entirety of the project, including control over:

• Answering any questions the owners will have
• Costs
• Design
• Planning
• Time frames

As a result, homeowners are left with no way to properly check and balance their ADU development.

If you are looking to have full control with checks and balances in place while still having it easier on you, consider a Design Build Firm that does not tie in the design phase team to the build phase team. If this interests you, feel free to reach out to get more information.


Choosing ADU Professionals Based on Cost Only

When you go about choosing your ADU team of professionals, price should be your third priority.

Your first priority should always be the ADU professional’s experience and knowledge. The second should be their ability to effectively communicate and connect with you.

Most of the time, you cannot afford the most expensive professional, but that probably means you can’t afford the cheapest one either. Why? Well, it is because, in the long run, the lowest-priced professional is always the most expensive.

They cost the most because often they are:

• Difficult/impossible to communicate with
• Going to change orders (leave out information initially so they can add costs later)
• Going to cost you more money due to their mistakes that will need fixing
• Inexperienced
• Slow to move (take forever to do the job when time is money)


Trying to Use Premade ADU Plan

There is an abundance of premade ADU or small home plans that are great if they fit your needs. However, most of the time they don’t due to your specific situation.

These premade plans may not be suitable for you because everyone has different:

• Budgets
• Level of changes or customizations they are looking for
• Property conditions

A true custom ADU is one-of-a-kind. Depending on what you are looking for, trying to force an existing plan to fit your project can be like trying to fit a round peg into a square hole. It is just not going to work well for you.


Not Spending Sufficient Time in the ADU Design Process

Changes on paper are simple and much less expensive than changes made once construction has begun. It is important to spend quality time during the design process to optimize how your new ADU will live to avoid potential costly changes once the process is further along.

Poor Overall ADU Planning

When designing your ADU, you should take your potential tenant’s lifestyle and habits into consideration. Even if you are the one who is going to live there, think about how your needs will change as you age.

Ask yourself questions like:

• Is it for a single person, couple, small family, or larger family?
• Will you need to accommodate safety features for new or young children?
• Do you need to think of your needs later in life as you reach retirement age and beyond?

These are important questions to consider during the planning process. The last thing you want is to invest a lot of money into an ADU that will not work for you in the future. Always think ahead to see where you will be and what you will need from your ADU.


Not Planning for Enough ADU Storage

Unless you have plans to develop a large ADU, space planning and design are crucial.

Always pay close attention to where you place your storage space, as this can be a challenging process.

Ask yourself questions like:

• Does the master bedroom need a walk-in closet?
• How many closets are needed?
• Should the common area be larger?
• Should there be more space in the bathroom?
• Where should the closets be placed?

Deciding how many closets you need and where to place them can be tricky. You will need storage space throughout your ADU, but too much will start to take away from your living space. This is why it is important to find that perfect balance.

In general, you should have a closet in each bedroom and in either a hallway or common area. Try to think ahead to your tenant’s needs. How much storage is enough to comfortably accommodate all their things without making some living areas too small?


Not Having An ADU Laundry Area

Never compromise on a laundry area.

We have found that having an area to do your laundry within the ADU is an important amenity for most people. Even people who decide they do not mind going to the laundry mat quickly regret their decision after living in their ADU.

If the ADU is big enough to accommodate a laundry room, do it. If not, consider adding a laundry closet. Depending on the amount of space you have, this closet can be big enough to fit two laundry units side by side or on top of one another. It is up to you and your space availability.

If your ADU is so small that it cannot accommodate a laundry closet, then plan for a two-in-one washer and dryer to go under the kitchen counter. We guarantee you will thank us later.


Second Guessing Yourself at Every Turn

You will make dozens of decisions about designing and building your ADU throughout development. An important thing to keep in mind is that your initial gut feeling is often the best decision for you. Second-guessing yourself throughout the process will only cause stress and delays. When doubts arise, rely on your team – there is a reason you chose them.


Overspending on An ADU Conversion

It is a common misconception that remodeling is always cheaper than new construction. Due to this, most people believe that a garage conversion to an ADU is less expensive than building a new one.

In most cases, this is true. However, remodeling may not be cheaper depending on:

• The condition of the garage
• The final design of the ADU
• The location of the garage on the property
• What you are trying to achieve

If you are thinking of building a large-scale ADU, it is worth a conversation with your designer and builder about what makes the most sense for your project. You might find that building a new structure will save you loads of money in comparison to converting your garage.


Not Comparing ADU Construction Estimates

Most homeowners will ask a contractor to provide an ADU construction estimate/bid based on their plans and designs. However, they do not always provide all the information needed to the contractor to make an appropriate estimate or properly compare the given estimates from different contractors.

The worst mistake a homeowner can make is to receive an estimate without any designs or plans in place. Doing this will lead to incomplete estimates that cannot be compared against one another.

Your first step should always be to put together designs and plans. Your second step should involve developing a scope of what work will be needed to supplement your plans.

Whenever asking for an estimate, make sure you always include information that will not show up on your plans and describe your expectations. This is the only way to ensure you get the most accurate estimates possible so that you can properly compare them to one another.


Homeowners Giving Direction to Subcontractors

Workers and subcontractors are not the ones to communicate with or give instructions to during construction. They are there to do the portion of the job that is given to them by the general contractor.

If you give workers directions, they may act on those without consulting the contractor, resulting in potential mistakes and confusion.

To avoid this, you should only ever discuss your ADU with the builder. They are the only ones who have all the information concerning the project and can accurately determine if your instructions are doable or not.


Not Leaving Money for Contingency

Almost always, something will occur during a development that was not accounted for in your original budget. Don’t worry, this happens even with the best-laid plans.

For this reason, we always recommend having a contingency fund. The amount of the contingency fund varies depending on each person and project. As a general rule though, plan for a minimum of 10% of your overall budget.


Developing an ADU Can Be Easy

Here at Levi Design Build, we offer a personalized approach to designing, planning, managing, and building your ADU. We can help you avoid these mistakes along with others to ensure you get the most out of your investment. Just remember, do your research, and hire a reliable ADU Design Build firm like us to ensure a smooth and easy experience.

After all, it is our commitment to provide you with the highest service throughout the entirety of your project.