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Homeowners' Guide to Modular ADUs

Modular ADUs: Everything You Need To Know About Modular Accessory Dwellings

If you’re looking for a durable and low-maintenance home, a new modular ADU is a great option. Proper care can make it last for decades and provide a comfortable place on your property that would give room for guests or extended family, generate income from a renter, or even serve as your own private home office. There is a reason why these secondary housing units are promoted as a solution to the housing crisis. The flexibility that they offer to the property owners is amazing. The property owner can live in it herself and rent out the main house. Or use it as an in-law suite for older relatives – rare single-family home is equipped for an aging family member.


Modular Accessory Dwelling Units (ADUs) can be an excellent solution for optimizing limited real estate. These fully customized livable units are easy to install and offer numerous advantages over traditional construction methods – including modern designs, time savings for work in your backyard and efficiencies in buying raw materials.


Custom ADUs take much longer to design. If you have found a floor plan that fits the bill, this is the best shortcut to get your ADU project started. If the modular ADU comes with a pre-approved stamp from the city or from the State, this has significant impact on the speed of getting your building permit. Stick-built ADUs, same as any custom home, make anything possible – from large windows to a dedicated laundry room. But the starting cost is higher, the necessary permits take longer. Modular ADU owners see increase in their property value much faster.


Let us explore the benefits of modular ADUs in-depth and uncover tips on investing in one! Read on to learn everything you need to know about these convenient dwellings. Not all backyard homes are tiny homes! Not to be mistaken for mobile homes either!


You will still need a general contractor for all site work. But typically construction takes about a month before the unit arrives and less than a month after. Weather permitting of course. The entire process creates less mess in your backyard and less waste. Building site work is governed by the local laws, so your general contractor needs to be familiar with local regulations.

L shape modular ADUs by Inspired ADUs

Modular ADU Homes 101

Modular ADUs, also known as accessory dwelling units, are prefabricated and transportable dwellings that can be used for various purposes. They are small dwellings typically built in a factory setting using modular off-site construction techniques. Modular ADUs can range from simple shed designs to more complex living spaces – always with full kitchens and bathrooms.

By leveraging prefabricated building components, modular ADUs can be built quickly and economically. Modular homes and ADUs are becoming increasingly popular with US owners of vacant land and single-family homes with big backyards. They provide an affordable way to add living space without a long-term commitment or the expense associated with traditional construction methods. Imagine getting a house with all interior finishes completed on day one.

Why Modular Homes?

Modular ADUs offer a unique solution to the growing demand for affordable housing. They are prefabricated structures that can be quickly and efficiently delivered and install, eliminating the need for lengthy construction timelines.

These factory-built homes are typically constructed with materials that resist weathering, providing long-term protection from harsh elements. Additionally, modular ADUs are somewhat customizable, allowing personalization to fit various needs and preferences. Just remember to check what has been pre-approved – not to get caught in a long permitting process at the State level.


When choosing between a modular or conventional ADU build, several factors must be considered. Modular homes are typically less expensive than traditional builds, requiring fewer materials and labor costs.

Furthermore, modular ADUs can be constructed in a fraction of the time it takes to build a conventional home – they literally get built while your on site contractor is building the foundation. In addition, these homes come with many energy-efficient features that can save homeowners money on utility bills over time. Modular ADU designs often boast a modern look, come with built-in storage, luxurious glass doors for natural light and energy star appliances. Keep checking what is included in the base price – to make sure you are not asking for upgrades that will create a budget issue down the road.

Pre-designed home has another benefit – it lets you make less decisions on what needs to go into the house.

Can A Modular Home Be An Adu?

Yes, a modular home may be used as an ADU. Modular ADUs are becoming increasingly popular due to their affordability and convenience. With modular construction, the units are built in a controlled factory environment with consistent quality assurance standards.


This ensures the team is finished quickly and accurately according to the approved building plans.


Modular ADUs typically come in two parts: the structure and the foundation. The system comprises several pre-manufactured modules, which are joined together on-site.


Typically, these modules range from 300 sq ft to 1200 sq ft and can be customized with features like energy-efficient windows, doors, and appliances. Every square foot matters. Make sure you like the location of water heaters and washers. Would you be OK with either one in your bedroom?

Visit the showrooms to make sure you like what you will get

Modular ADUs in detail

shower in a manufactured home
Manufactured home

Shower space

Obviously, the size will be to building code. The question is, can you live with this aesthetics?

Modular home

Shower space

Tiny details make modular homes have this unmistakable modern look. Black details. Wall mount toilet.

kitchen in a manufactured home
Manufactured home

Kitchen appliances

The appliances come in their pre-designed spots. Make sure it will not bother you every day for the rest of  your life.

kitchen layout in a modular adu
Modular Construction

Some items are required for ADUs: a cooktop, a hood, a sink. A dishwasher? A building inspector does not care. Do you?

laundry hook up in a manufactured home
Manufactured home

ADUs are compact homes, having space for a laundry is a bonus.

Modular home

The location of the washer and dryer is also set in the plans. Can you live with it?

2Bed / 1 Bath

Modular ADU Floor Plan

Small 570 sf ADU
Other floor plans available

A modular 2 bedroom 1 bathroom unit

This smaller ADU floor plan of 580 sf includes two bedrooms on opposite sides of the unit, a living space with a kitchenette in the middle, and a bathroom with a stacked washer/drier.

Pricing starts at $220,000 for the modular unit itself, entitlement (surveys, plan set, building permit fees), transportation and crane. Site work (foundation and utilities) depends on property specifics and will add ~$170,000+ to the budget.

Overall, it typically takes 3 months to permit, 2 months to prepare the site, one day to install the unit, 2 weeks to build the deck, connect utilities and complete the project.


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FAQ about Modular Homes and ADUs

Modular homes and ADUs: homeowners' crash course

Which Is Better, A Modular Or Manufactured Home (HCD Vs. HUD Standards)?

When it comes to the debate between Modular ADUs and Manufactured Homes, there are a few key differences that should be considered.

Modular ADUs are manufactured off-site by local building code requirements and then delivered to the job site, where they are typically assembled on permanent foundations (Modular Homes) — this is known as a “modular stick-built” construction model. This type of construction is relatively inexpensive and fast compared to traditional on-site builds and offers more flexibility in design than manufactured homes.

On the other hand, manufactured homes are constructed off-site following Uniform Building Code (UBC) or HUD standards and delivered as a single prefabricated unit. Manufactured homes are usually installed on a permanent or temporary foundation and secured to the ground with tie-downs.

They are typically less expensive than Modular ADUs, but offer fewer design options due to the standardized building codes they must adhere to.

Why Are Modular Homes Better?

The first benefit of modular homes is time savings. Building a traditional structure from the ground up can take months or even years. Modular homes, however, are prefabricated in a factory and built to local building codes. This allows them to be delivered and installed quickly, usually taking only weeks instead of months.

The second advantage is cost savings. Building with modular can often be cheaper than traditional construction since it is more efficient. Manufacturers can often reuse materials, which lowers both cost and waste. Additionally, since these homes are built in a factory environment by trained professionals, the risk of costly mistakes on the job site is reduced significantly.

Where Are Modular Homes Built?

Modular ADUs are built in factories and then delivered to their intended destination. The modular units are typically transported via flatbed truck and require a crane to move them into place on the foundation.

This type of construction allows for a much faster build time than traditional building methods, saving time and money on labor costs. In addition, because the modules are built in a factory setting, quality control is more easily enforced, ensuring that the ADU will be of a higher standard.

Will Modular Homes Last?

The answer is a resounding yes. Modular homes are built to the same quality and safety standards as site-built homes, some surpassing them due to their factory assembly process.

This allows for tighter tolerances, higher-grade material use, and a more consistent level of craftsmanship across all the components. The walls, floors, and ceilings are also built with more structural integrity to withstand rain, wind, and snow – and transportation. Plus, modular ADUs can be designed for long-term durability.

How Sturdy Are Modular Homes?

Modular homes are built with the same materials and techniques as traditional stick-built construction, offering the same strength and durability. The modules are precision-engineered in a factory to withstand heavy wind loads, seismic activity, extreme temperatures, and other environmental conditions. They also come with certifications from third-party engineering firms that guarantee their structural integrity.

Because they’re engineered in a factory, modular homes are held to higher standards than traditional stick-built construction. Rigorous quality assurance processes ensure that all components fit together correctly and the buildings are built to last. Many of these prefabricated dwellings have impressive warranties that guarantee the structures for up to 30 years.

How Durable Are Modular Homes?

Modular ADUs are designed to meet the same standards as traditionally built homes, and many of them come with warranties that cover artistry and materials. They are constructed using high-quality materials and precise engineering to resist wear and tear better than traditional structures.

The walls and roof panels are typically constructed from steel or reinforced concrete and engineered wood, designed to withstand extreme weather conditions. The windows and doors are also designed for durability and energy efficiency.

Modular ADUs can stand up to the elements for decades with minimal maintenance. They come with a tight building envelope that helps keep air leakage out of your home, thus reducing energy costs. The rigid frames and panels can also provide a strong foundation for your home that is less likely to warp or crack over time.

Will Modular Home Prices Go Down?

Modular ADUs are becoming increasingly popular as a cost-effective way to build and add additional living space. As with any product, the more it is produced, the lower its costs can become. Modular ADU manufacturers are now making orders in larger volumes, and this increase in production can decrease consumer prices. This is because production costs can be shared across multiple orders, lowering individual prices.

Watch out for transportstionand crane costs though, as they can easily eat up all the savings.

Will Modular Home Increase In Value?

The short answer is yes; Modular ADUs can increase in value if built on a permanent foundation. This type of structure has been gaining popularity over the past few years for its affordability and versatility since it can be used as an ADU or primary residence. As such, when appropriately constructed with quality materials, a Modular ADU can add value to your home based on its design, size, and features.

Well-crafted modular structures are made with quality materials that can last for decades. These prefabricated homes come in various styles and sizes that can be customized to fit your needs. In addition, they are usually built with energy-efficient features such as insulated walls and roofs, dual pane windows, and metal siding to help reduce the cost of utilities.

Can Modular Homes Be Moved?

Absolutely yes! While it can be expensive to move a modular home, it’s not impossible. Modular homes are built in sections and transported to their final destination, where they’re assembled on-site. Depending on the size and complexity of the individual modules, transportation can range from just a few sections atop a flatbed truck to a whole convoy of vehicles for larger homes. Once at the destination, all units are connected and placed on their permanent foundation.

Moving a modular home is usually handled by a professional moving company specializing in modular housing transportation. They will have the necessary equipment to securely transport your home from its starting point to its final destination.

After the move, they’ll also be able to make any necessary adjustments or repairs. Afterward, all sections will be reconnected and secured on their foundation.

Can Modular Homes Be Remodeled?

Yes, modular homes can be remodeled! Modular ADUs provide the perfect solution for homeowners needing extra living space without undergoing a full-scale construction project. These units come in various sizes and configurations and can easily be modified to fit your needs. For instance, you can customize the interior layout, add windows and doors, or even expand outward.

Modular Home Module Sizes

Modular ADUs come in various sizes, but most are small enough to fit on a standard truck. This makes them easy to transport and install. The average width of a modular ADU is around 14 feet due to state regulations for their transportation.

However, some units can be as small as 200 square feet or as large as 1,000 square feet. Size options depend on the manufacturer.

At the same time, modular ADUs are designed to be modular, meaning they can be configured into different sizes and layouts. This allows you to customize your unit’s size and shape to fit your needs best.

Is Modular Worth It?

When deciding on the best way to construct an ADU, knowing whether modular ADUs are worth it can be challenging. Modular ADUs come in various shapes and sizes, from small one-bedroom units to spacious three-bedroom homes, and offer many benefits over traditional construction methods.

Modular ADUs are built off-site in a controlled environment and then transported to the home’s location. This way, they are constructed with precision, down to every detail. As such, they tend to be much more modern, energy-efficient, and cost-effective than traditional construction methods.

Additionally, modular ADUs save time, as they can be constructed in a fraction of the time for conventional on-site construction.

Another great benefit of modular ADUs is the wide variety of customization options. With modular ADUs, you can choose from various materials, styles, and finishes to create an aesthetic that fits your needs and lifestyle. From sleek and modern to rustic and traditional, modular ADUs offer great flexibility in design.

Modular ADUs offer flexibility, efficiency, and customization, making them an attractive choice for those looking to build an accessory dwelling unit. From their construction in a controlled environment to their wide range of design options, modular ADUs provide many benefits over traditional methods.

When considering the pros and cons of building an ADU, modular construction is a good option worth considering.

Trade off for a Custom Floor Plan

What fun will you miss with modular construction?



The modules arrive ready to live in. All waste happens on the factory floor.

drywall dust while finishing drywall before painting it
Time gains

Drywall prep dust

You won’t have to deal with dust. The ADU prefab will arrive painted. There may be some cracks caused by transportation, but they are minimal.

waterproofing shower space
Time gains


The bathrooms will be ready to use as soon as your local plumber connects the unit to the water and sewer or septic lines.

selecting grout to match tile color
No Analysis Paralysis

Color selections

Most modular companies have pre-designed sets of color combination. You do not have to sweat the details.

measuring sink
No Analysis Paralysis

Making sure the fixtures work together

You won’t have to make sure the sink is of the right size and the faucet had enough reach for comfortable use. 

tile and countertops
Stress level down

Control of lead times

You do not have to make sure the appliances, fixtures and finishes arrive on time for different trades. It’s the factory’s headache. 

Other floor plans available

Some of our 300+ plans are modular ADUs

There is a number of pre-designed floor plans in our library – we have I shaped ADU, L shaped ADU and more.

Every thousand dollars matters when you look at an ADU as an investment into your property. This is why we try to save you money with pre-designed plans. 

It is also a reason why we consider many parameters of your site and personal requirements when giving you a recommendation. As you know now, modular ADUs can also come in different shapes, sizes and materials. There are multiple options for  foundations and  exterior looks. Not every one of them will work for your backyard.


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