Small but totally independent second houses are a trend nowadays. Lots of modern homeowners construct them because of their versatility, convenience, and ability to increase property value. For such a house, even 400 sq. ft. with one bedroom can be enough. It may fulfill different practical purposes — a granny flat, a guest house, a home office, a personal mini-cinema, or an art studio. You can also use it to generate rental income. With efficient design, the right ADU floor plans, and some optional add-ons, you may give it a rather spacious feel and even turn it into a combined living area.

In our article, we’ll talk in detail about the main characteristics, types, and advantages of 400-square-foot ADUs.

Types of 400 Square-Foot ADUs

Firstly, let’s give a definition of an ADU (accessory dwelling unit). It’s a secondary home that shares the property with the main one.

There are many ADU design types and variants. Usually, specialists divide them into several large categories:

1. Attached. These accessory dwelling units have a connection with the main home — typically a wall or even a roof. Such an ADU floor plan is perfect for aging family members with specific needs;
2. Detached. It’s a completely separate living area. A detached ADU can be a great living space for guests;
3. Converted. This is an already-existing building (for example, a garage) turned into an accessory dwelling unit. It’s the cheapest and easiest ADU to create because its outer walls are already here. You’ll just need to make some modifications — change its space layout, install windows, inner walls, and the main entrance. However, getting a permit is necessary for it too;
4. Junior. It’s a small dwelling unit whose size mustn’t exceed 500 sq. ft. In California, you can create it on your property, even if you already have an ADU of any other type.

Also, ADUs can be prefab or stick-built. The first type is a living space constructed in a factory. It requires a minimal building process (or none at all). It’s faster, more convenient to make, and sometimes cheaper, but its floor plans are not customizable. The second type is a traditionally-constructed ADU. You can customize its drawings as you wish, change its bedroom type roof size, add some extra storage space, and so on.

All those ADU types are completely habitable. Their floor plans can include a bedroom, a bathroom, a kitchen, and a living room.

400 Square-Foot ADUs: the Biggest Advantages

Tiny houses have multiple benefits in comparison to larger ones.

The main ones are the following:

• Faster completion and lower maintenance. The smaller a home is, the easier it is to create and maintain afterward;
• Availability. Not only does the building itself have lower pricing, but all the payments connected to it are also significantly smaller — mortgage, temperature regulation, electricity, and so on. Moreover, in California, ADUs are smaller than 750 sq. ft. Aren’t subject to impact fees;
• Fewer materials, decorations, and furniture, which is also can help you save lots of money;
• The necessity to live a more active life. A tiny home may be comfortable and have a cozy interior, but its square footage is not large enough to spend the whole day inside it. So, you’ll need to go outdoors more often, which is a far healthier lifestyle.

So, a 400-square-foot ADU floor plan can be an ideal option for you. It has plenty of advantages in comparison to larger houses. Also, despite its small size, it can have features such as a storage loft, clerestory windows, and many others.

If you want to get this tiny home in your own backyard, contact us and order our services. A+ is a general contractor company that has all kinds of professionals, including designers, builders, and structural engineers. We can do every part of the construction process, from estimating the costs and making the ADU floor plan drawings to doing site work and interior design. By the way, we offer cost estimation completely for free in a very convenient file format!

Frequently Asked Questions — FAQ

What does a 400-square-foot space look like?

If you’re unsure what this size resembles, you can imagine a large bedroom or a big garage. Such an ADU is comfortable, functional, and suitable for living. It can be a full-fledged housing unit whose floor plan includes a bathroom, a toilet, one bedroom, and a kitchen with a table and a seating area. But, of course, it isn’t very large.

How much does it cost to build a 500-square-foot ADU in California?

Typically, a modern 500-square-foot ADU costs around $150,000. Its price depends on the ADU floor plan, its type, location, additional features, and other details.

What is the cheapest option for an ADU?

The cheapest ADU design variant is a garage or room conversion. Its cost usually around $110,000. To convert a garage, attic, or basement into a living space, you won’t need to construct walls — you’ll only have to change its layout (make a bedroom, a kitchen, a bathroom, etc), add interior design, furniture, utilities, and decorative features.

Is it worth it to build an ADU in California?

Of course, it is! In addition to multiple functions that an ADU can fulfill (a granny flat, a home office, a guest house, etc.), it can significantly increase your property value. In most cases, property parcels with ADUs cost 20-30% more than without them.