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The Ultimate Guide to Building Your Accessory Dwelling Unit (ADU)

Love the home you live in but need more space? We get it. Families grow and needs change over time. Sometimes, your home has to grow and change with you. Perhaps the time has come to consider a mother-in-law apartment for aging loved ones, or maybe you're ready to increase your home's value and create a source of passive income with a rental unit.  Adding a secondary living space or accessory dwelling unit (ADU) to your property is a great solution but the idea can come with many questions. 

What is an Accessory Dwelling Unit?

An ADU is a smaller secondary dwelling unit that shares the building lot of a single-family residential home. ADUs go by many names – such as:

  • Attic apartment
  • Granny flat
  • Backyard cottage
  • Garage conversion
  • Basement apartment
  • Mother-in-law suite

What are the qualifications of an ADU?

For a secondary dwelling unit to legally qualify as an ADU, there are a few features it must have:

  • It must have a foundation (can be its own foundation or a shared foundation with the primary house)
  • It must have legal access to water, sewer, and utilities.
  • It must have a fully functional living space – living room, kitchen, bathroom, and bedroom.
  • The square footage should not exceed 1200 sqft.

What are your reasons for building an ADU?

Before you start planning and building your ADU, ask yourself why you want to build an ADU? Is it to allow an elderly loved one to age near family? A multigenerational living solution? A special needs loved one who can't live on their own? Or are you looking to capitalize on the rental market? Fleshing this question out will help you determine which ADU type is best for you and your home.


What Type of ADU is Best for Your Home?

Interior ADU – this is a fully functional apartment often built in the basement or the attic.


Attached ADU – this unit shares at least one wall with the primary residence.


Detached ADU (DADU): A freestanding independent living space. LEARN MORE ABOUT DADUs


What space does your property have available?

The size and shape of your property will also play a vital role in which ADU type you choose. Do you have room to build out from your home? Or do you have an attic or basement that is sitting unused? Or maybe you don't need that extra garage space after all. The key is to find the balance between what your property size allows, what your loved ones need, and your budget.

What to budget for and what contributes to ADU building costs?

Here are a few common cost factors to consider when you begin planning your budget for you ADU:

  • The type of ADU you are choosing to build
  • Are you building the ADU as an addition or just remodeling a space such as an attic or basement?
  • Your location – your city, county, or even neighborhood may have ordinances you must follow.
  • Do you need new hookups, or are you retrofitting existing utilities?
  • The size and design of the unit
  • Material costs
  • Permits
  • Landscaping
  • Professional fees – such as construction crew
  • Furniture

The key to keeping the costs within your budget is strategic planning and investing in materials that are essential in ensuring a strong and sturdy unit. Working with a professional construction company can help mitigate the worries and concerns of unforeseen costs.

If you're considering adding an Accessory Dwelling Unit to your property, our team at Verum Construction can walk you through the process from start to finish. We'll explore the many different options with you, help you understand the ins and outs of the ordinance and zoning laws, and make sure your project is designed and completed according to your specific needs and vision. Our Truth In Building Process ensures that every step of the way you'll know exactly what to expect so there are no surprises. Contact us today to get started on your new ADU.