Prefab granny flats are one of the quickest and easiest ways to add an ADU to your property, but we’ve found there’s a lot of common misconceptions about this building technique.

Concerns such as price, durability, customization, and more are often miscommunicated to clients. We’re here to debunk those myths and give you the facts.

First, what is a prefab?

Prefabricated homes, often referred to as prefab homes or simply prefabs, are specialist dwelling types of prefabricated buildings, which are manufactured off-site in advance, usually in standard sections that can be quickly shipped and assembled.

Myth: Prefabs are the cheapest option for a granny flat

While building the prefab itself is pretty cost-effective, there are several aspects that need to be taken into consideration. 

Let’s say you have your eye on a beautiful 600 square foot ADU with a great layout. Average prefab granny flats in California will cost about $100 per square foot so your total so far will be $60,000. 

Now let’s break down the rest of the costs. 

prefab granny flats

First, you have to prepare your site. This will include setting the spot with a mixture of asphalt and concrete and making sure it’s compacted. This step will cost about $7,500+. 

Next, you have to transport your ADU to your property which will cost around $2,500+.

Finally, comes the exciting part: installation. Installation could cost up to $15,000 which includes the crane rental. 

The grand total comes out to about $85,000, not including permit fees. 

This total is very similar or even a bit lower than other building techniques, so rather than using cost as the main factor in your decision, we recommend doing your research to see what method works best for you. 

Myth: Prefab granny flats are not as durable as conventional stick and build ADUs

The truth is quite the opposite.

Prefab granny flats are actually considered MORE durable than the conventional stick and build method. 

Think about transportation. Your prefab ADU has to travel all the way from the factory to your property, going 50-60 miles per hour down a highway that may or may not be very smooth.

A structure in this scenario is similar to being in a seven-point earthquake.

Prefab manufacturers build their ADUs with this exact issue in mind. A prefab needs to withstand a large amount of shaking and rattling and then be lowered by crane onto your site. 

Myth: Prefab granny flats are not customizable

Just because these structures are pre-designed does not mean there isn’t room for customization. 

Changes such as ramps, room sizes, window placement, and much more can be made to suit your needs and lifestyle. 

All you need to do is schedule a consultation with the prefab designer and they can walk you through how they can alter the structure into your dream ADU. 

prefab granny flatsJust keep in mind that changes do come at a cost. It’s important to communicate with the designer to know exactly what the final cost will come down to. 

If you need to make drastic changes to the available designs, consider either the traditional stick and build method or a panelized modular. 

Panelized modular is where the framing package for your ADU is built offsite and shipped to the job site. Unlike prefabs, however, this type of construction is completely customizable but takes longer to construct.

Myth: Any contractor can install prefab granny flats

ADUs are still part of a niche in the housing market but that niche is growing fast. This means many contractors may be trying to jump headfirst into ADU projects without the proper knowledge. 

Installing a prefab home is drastically different from installing a prefab ADU. There are lot requirements, setbacks, permits, and many more regulations that need to be considered. 

Although ADU requirements are a lot more progressive ever since the latest ADU bills were passed, there are still quite a few rules that need to be followed. 

Hiring a contractor that has no ADU experience could:

  • Add months to your construction  and permitting timeline
  • Put you at risk of installing an illegal ADU
  • Cause your ADU to be installed incorrectly

Save yourself the headache and hire a contractor that has experience in installing prefab ADUs.

One of our ADU experts can connect you with a credible licensed contractor. Schedule your Site Evaluation here! 

Myth: Prefab granny flats can be installed in a day

It can happen, but realistically, expect the process to take at least a few days to a week.

prefab granny flats

As mentioned before, your site has to be prepped, then your ADU needs to be lowered by the crane. Once that’s completed, you still have to install the plumbing and electric. Finally, just a few details are left to accomplish and your ADU is good to go.

However, a week is still a big improvement than having to deal with six months of construction, which is the average for the traditional stick and build method. 

Is a prefab granny flat the right option for you?

Just like with any building method, there are pros and cons to prefabs. If you’re willing to overlook the limited customization in favor of a quick installation, then we highly recommend this method. 

The quick installation is great for homeowners that live in regions that endure extreme weather like snowy seasons or intense dry heat. Your ADU can be done quickly without the risk of delay due to weather conditions. 

Maybe you just don’t want to deal with months of loud and messy construction? Then a prefab is the way to go for your ADU project.

If you’re still unsure, you can schedule a free phone consultation with one of our ADU experts to find out which method is the best for your project. 

Are prefab granny flats good investments?

prefab granny flats

Credit: Prefab ADU

Depending on your situation, they most definitely can be a great investment. In fact, adding any granny flat onto your property will greatly boost the value of your home. 

Not only does an ADU add monetary value to your home, but also keep in mind the added benefits to your lifestyle.

Whether you build one to house an aging family member, rent it out to an individual, or use it as a guest house for visiting friends and family, an ADU has a multitude of uses that will make your life easier.

When the time comes for you to sell your home, the granny flat will definitely add resale value in comparison to a home without one.

Do prefab granny flats hold value?

Your prefab will appraise for the same as a stick and built structure. It also will not depreciate in value. 

The value of your prefab granny flat will depend on your area’s current housing market so if you live in an area with a strong market, you’ll see a great return on investment on top of all the other benefits.

prefab granny flats