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Cost to Build ADU: What You Need to Know

January 15, 2022 By Admin

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Reports show that the U.S. housing crisis continues, with supplies dropping by another 12% since last year. This leaves around 10% of the population with a problem when it comes to finding accommodation.

Perhaps you’ve experienced this first-hand through a family member’s struggles to find somewhere affordable to stay. You’d love to help them out, but your home is at a bursting point with children unable to fly the nest.

Building a granny flat could provide an answer to either of these difficulties, but you’re probably wondering about the cost to build an ADU? Keep reading to discover more about ADU construction costs.  

Blue shed addition in backyard at sunset

Breakdown of the Cost to Build an ADU

The purpose of your ADU has a big impact on the building costs. It affects the size of the building, its location, and interior fittings. For instance, an elderly relative might need an attached ADU with easy access to the house and features suited to limited mobility.

A university-age child will want a space for independent living, privacy, and modern conveniences. These factors impact the overall design of your ADU, so keep them in mind throughout the process.

Tiny white house at end of path with wooden barn doors

Average ADU Building Costs

Most builders will quote their price in square feet. This can vary from under $150 per square foot to over $300 per square foot depending on the materials you choose.

For example, prefab ADU cost considerations are less than those for building a brick and mortar or wood ADU. 

With this in mind, you can expect to pay around $160,000 for an 800 sq. ft. ADU. Your location can also affect ADU building costs. In California’s Bay Area, the average cost to build an ADU is about $350,000. 

The type of ADU you’re building will influence its size and cost per square foot considerably. For instance, basement ADUs and other attached ADUs will cost less, since some of the structure is already there. 

These average prices refer to the physical construction of the ADU, there are many extra costs to consider, too.

Tiny brown house in the desert

Before Your ADU Builder Gets Started

You’ll need to complete several steps before you start building your ADU, and some of them attract additional costs.

You must get approval from your city, county, and neighbors, and hire an architect to design your building. An architect usually charges 10 to 15% of the project cost for their services.

In some cases, you might even need assistance from an engineer, and you must ensure your ADU complies with environmental regulations, too.

Once you’ve got your design, you’ll need to secure the necessary permits to build your ADU.  

According to https://actonadu.com/, you can cut down on some of this expense and hassle by buying pre-approved ADU plans. 

Luxury guest house beside outdoor pool

Hidden Costs Associated With ADU Building

Apart from all the above costs, you should keep in mind that some extra expenses could crop up along the way. These include:

Utility Upgrades

Do you live in an older home? Chances are your electrical panels can’t support a second living unit. Most of these houses have 100-amp panels, but you’ll need at least a 200-amp panel to add an ADU to the picture. 

Upgrading your electrical panel could set you back a few thousand dollars, so speak to an electrician about this issue while setting up your budget. 

Extra Site Work

Do you have uneven ground at your preferred ADU site? What about large trees? You’ll need to address both these aspects before you start building. 

Hiring a team for additional site preparation is an expensive undertaking, so make sure you find out the costs in advance. 

Construction Delays

It can take as long as 12 months to build an ADU if everything goes according to plan. Yet, days of bad weather can slow or halt construction, drawing out the process even longer.

If you’re intending to rent the unit out for extra income or housing your relatives elsewhere while you build your ADU, keep this in mind.

Extras Associated With Construction

While you have a team of builders on site, you might need to pay for a few extras like site security, porta potty rental, and waste disposal. Don’t forget to factor sales tax into the picture, too.

Rustic ADU with blue door

Steps Involved in Constructing an ADU

Often, waiting for authorizations and permits can take longer than the construction process. So, make the best use of your time while you’re waiting.

Use these months to source professional ADU builders and get quotes. While discussing construction costs with your builder, and comparing quotes, you shouldn’t lose sight of all the aspects involved in constructing an ADU.

These are the steps involved:

Site Preparation

This should include clearing vegetation, grading, and any necessary demolition. Then they’ll need to excavate the site and lay the concrete foundation. 

Framing 

Framing the structure includes setting up the walls, joist, roofing, windows, and doors. Ask your builder if their costs include exterior trim like gutters, flashing, etc. 

Installations

The quote should also include installing the necessary HVAC, electrical, and plumbing solutions. If not, you’ll need to hire additional contractors for these aspects. 

Interior Finishing

Insulation, stairs, millwork, handrails, and drywall as well as ceiling, wall, and floor finishes come next. Will your contractor take care of installing kitchen appliances like stoves and washing machines?

The final costs associated with building an ADU are the patio, sidewalk, driveway, and landscaping. 

Blue ADU with white trim and rustic farm elements

You Won’t Regret Building an ADU

Now that you’re more familiar with the approximate cost to build an ADU, you’re in a better position to decide what’s best for you.

ADU’s work well for long and short-term rentals, too. So, when your family members move out, your ADU won’t go to waste.

You can also use it as a home office, gym, or studio, and get your money’s worth that way. 

Would you like to find out more ways to add value to your home? Browse our blog for all the best home design inspiration. 

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