What is prefab ADU and how is it different from any other ADU? Prefab refers to the building process and it gives many benefits over traditional site-built construction. Before we dip into what this means for you, let’s cover a few basics.
What Is An ADU?
ADU stands for Accessory Dwelling Unit- secondary homes built on the same property as a primary house. Granny Flats or Backyard Dwellings are other terms for ADUs. They have their own entrance, living area, bedroom, and kitchen.
Adding a Backyard Dwelling (ADU) to your property can provide rental income or housing for extended family. ADUs come in two variants: traditional site-built and prefabricated ADUs. The major difference is that one is constructed onsite and the other off-site (like in a factory).
We’ll look at the differences later on, but for this article, we’ll focus mainly on prefab ADUs.
What Is Prefab ADU?
A prefab (prefabricated) ADU is built wholly or partially in a factory. The components are transported from the factory to your home and finished onsite. This type of backyard dwelling is the most preferred choice for many homeowners because they are faster to set up, convenient, and environmentally friendly.
How a Prefab ADU is Built
When we say our Backyard Dwellings are “built in a factory” you might be imagining conveyor belt assembly lines. The truth is a lot closer to the traditional building techniques you’ve seen around town – it simply happens in a controlled environment.
Skilled and tightly supervised contractors produce fully assembled modules like complete kitchens and baths. Everything is pre-installed- plumbing, electric, and HVAC as well as all the finishes and fixtures.
The components are shipped to your backyard and installed on a foundation in your backyard. The entire process takes just weeks, while a site built ADU could take up to a year to complete.
There are two main types of prefab ADUs: modular accessory dwelling units and panelized accessory dwelling units.
Modular ADU
Modular ADUs are prefabricated homes constructed off-site in sections (or modules) and transported to your home. Each module is nearly complete with fixtures, plumbing, electrical, floors and lighting. They are installed by crane or forklift onto a raised foundation before finishing.
Panelized ADU
Panelized accessory dwelling units have their walls built in a factory and are then transported and set up onsite. One thing that distinguishes panelized ADUs from modular dwelling units is that most of the interior, including plumbing, electric, and fixtures, are added and installed onsite. It takes longer than a modular prefab, but it is often less expensive.
Prefab ADU vs. Traditional Site Built
Site-built refers to the traditional method of construction that involves building the entire backyard house on site from the ground up. It is a lengthy, messy process with an unpredictable timeline.
The factory process of the prefab is tightly controlled- timelines and quality are more predictable. That is why prefab is becoming a much-preferred option for homeowners looking for a backyard dwelling.
Here are a few reasons prefab ADUs are now preferred over traditional stick-built ones:
Prefab ADUs take a relatively short time to build
- Prefab ADUs can be built faster than site-built dwelling units as most of the construction work is done in a factory under a controlled and supervised environment.
- A prefab ADU involves just 6 weeks of active construction time in your yard. Traditional contractors will be in your backyard for 8 months or longer.
- Many of the permits and inspections happen at the factory.
- Labor is more predictable as the workers have consistent location and working conditions.
- Weather related delays are eliminated
Prefab ADUs are more convenient
Everything is done for you – from design and engineering to permits to all the logistics. All you need to do is pick your model and options.
And nothing is more inconvenient than having contractors stealing your peace and quiet for months on end. With prefab the construction process is just a few weeks.
Prefab dwelling units are eco-friendly
The factory process means less construction waste.
The skilled laborers can live close to the factory, reducing the need for lengthy commutes.
Noise pollution is also reduced as the factory is a contained building located in an industrial area.
Is Prefab Method Less Expensive to Build?
Short answer? Yes.
It costs less to build, but the shipping and installation costs mean a prefab ADU is about the same price as a comparable quality site built ADU.
However, have you heard the old adage, “construction takes twice as long and costs three times as much”? The prefab process means we can commit to a cost and timeline in writing and upfront. Now that is convenient!
How Long Does It Take to Build a Prefab Home?
The entire process, from soup to nuts, takes about 9 months. This includes four months to obtain permits and three to four months to build the ADU in the factory.
Approximately 2 weeks before your Backyard Dwelling is due to arrive our crews will install your raised foundation and prepare the utility connections.
The actual installation takes one day, and then we spend a week or two connecting and cleaning everything up.
How Strong is a Prefab Dwelling Unit?
Contrary to what many people think, prefabricated homes are super strong. In fact, most prefab homes are structurally stronger than stick-built ADUs!
It makes sense if you think about it. Our ADUs are built to withstand being transported long distances- we include additional structural elements to make that happen.
And, because we are inspected and permitted at the factory, we have to meet the strictest building codes in the entire nation, not just the codes accepted locally.
How Does Your Prefab ADU Get to Your Home?
Once construction is complete in the factory, your prefab home is loaded onto a truck and driven to your home – we arrange all the transportation logistics with all the appropriate authorities. Depending on the type of prefabricated dwelling unit, we either use a crane or a forklift to move the ADU sections from the truck to the raised foundation installed in your backyard.
Is a Prefab Eco-friendly?
Our prefabricated ADUs are environmentally-friendly and sustainable.
The factory process means that material overages from one job are easily shifted to the next, reducing construction waste.
Bamboo flooring is an eco-friendly and sustainable material.
Solar energy panels are included in our ADU and all appliances are electric, reducing greenhouse gasses.
Also, workers who can live near the factory instead of driving long distances to job sites have shorter commute times, use less gas, and have more predictable schedules.
Ready to Own Your DIGGS Prefab ADU?
Are you considering adding a prefab accessory dwelling unit to your property? ADU DIGGS has your back! You only need to tell us what you want, and we take it up from there.
Have any questions? Contact us today.
