ADU Floor Plans 400 Sq Ft: Efficient Living

ADU Floor Plans of 400 sq ft are an efficient approach for owners with limited space and budget, featuring a bedroom and bathroom optimized for their needs. 

The main appeal of building an ADU floor plan of 400 sq ft lies in its comprehensive but compact footprint. Such granny flats can be designed to maximize living space and align with the aesthetics of the main property, making them a valuable, multipurpose addition. 

In this article, we will discuss the benefits of investing in a 400-square-foot ADU floor plan in detail. We will also examine what features to look for when building such a plan and how it can be elevated to offer an efficient living solution.

Why Do People Build 400 Sq Ft ADUs?

ADUs, short for accessory dwelling units, are an innovative strategy that targets the shortage of housing structures in various states. These granny flats are independent units built on the same lot as the primary residence, bringing multiple benefits to the homeowner. 

An ADU floor plan is mainly designed in an I or L-shaped structure and features a living room, kitchen, bathroom, and one or more bedrooms. While a larger lot guarantees additional living space, a more compact size, such as 400 sq ft, has its own advantages. 

RenoFi provides pre-approved ADU floor plans to get you started with the construction process on a more secure footing. We also provide the financing you need to build your dream ADU. RenoFi loans are ideal because they are based on the after renovation value of the property and increase your borrowing power. 

Here are some significant benefits of building an ADU on 400 sq ft that make it such an accessible, practical, and functional addition to any property:

Flexible Usage

An ADU of or under 400 square feet can ideally host an individual or a couple. The dwelling unit consists of one bedroom and a bathroom and is ideal for housing adult children and visitors. Aging parents and in-laws tend to find ADUs with smaller spaces far more comfortable to live in.

A 400-square-foot ADU floor plan also offers adequate space to renters and can be used as an Airbnb to generate extra income for the property owner. In addition, building a loft above the bedroom and bathroom area helps optimize space and squeeze in an additional office or storage area.

Affordable Construction Cost

The construction cost of ADUs varies greatly depending on the lot size and materials used. Given its space constraints, the construction cost involved in building an ADU floor plan for 400 sq ft is one of the most affordable options in the ADU landscape. 

A compact footprint helps significantly lower the price of installing utilities, plumbing, and other amenities in the unit. Another bonus benefit of building an ADU under 750 square feet in California is that there’s no need to pay an impact fee, saving the homeowner a considerable sum of money.

Boosting Property Value

ADUs are a great addition to any property, irrespective of their size. The 400 sq ft floor plans can be customized to complement the style of the main house and thereby boost the aesthetics of properties with limited backyard spaces. 

Small one-bedroom ADUs are ideal for homeowners who prefer a minimalist approach. Potential buyers also seek out these mini in-law suites, which offer a significant return value when the property is sold.

What Should a 400 Sq Ft ADU Floor Plan Include?

Building an ADU Floor Plan for 400 sq ft is a meticulous task. The right plan should take into account crucial factors such as local regulations, elevations, and roof foundation and ensure that the detached unit is built to efficiently manage space and budget simultaneously.

Here’s a look at what ADU floor plans 400 sq ft should include:

Cover Sheet

The cover sheet introduces the ADU project and includes the owner’s details, location, and other basic information. It may also feature a site plan with an aerial view of the ADU design and location relative to the already-built main property.

Floor Plans and Notes

An ADU floor plan is quite similar to that of an independent home. It consists of detailed, technical drawings of the structure. This plan also features the dimensions of all rooms, their relationships with each other, sizes, and other specific physical aspects at a single level. 

A floor plan may also list details like the roof and foundation layout. This drawing comes with notes and conditions that highlight the usage terms mentioned in the floor layout for better understanding,

Elevations

A floor plan elevation offers a precise representation of a single vertical plane. External elevations in ADUs refer to the external view from the granny flat and consist of features such as windows, siding, and doors. 

Remember that conversions of an ADU from garages, basements, or spare rooms are an exception and don’t require elevation drawings. On the other hand, interior elevations illustrate the interior walls, fixture placements, and tiles in the bathrooms and kitchen.

Utility Connections

Since ADUs are full-time dwelling units, they require complete connectivity to basic utilities such as power, water, and sewage. Depending on the property’s location, these connections are either installed in the granny flat separately or extended from the primary residence. 

The power plan details if the power is extended above the ground from the main house to the ADU or runs via an underground conduit from the power poles. Next is the sewer plan, which first identifies whether the primary foundation is connected to the city’s sewage system or has a septic tank system for waste. Depending on this, the sewer and water connections are planned and integrated into the 400 sq ft ADU.

Schedules and Standards

This part of the ADU floor plan contains the abbreviations, notations, and definitions mentioned in the document. It also features a schedule for constructing and assembling major ADU components, including rooms, windows, and doors.

Last, with varying local laws across different municipalities, it is important to verify that a chosen 400 sq ft ADU floor plan complies with the standard regulations to secure its permit. We at RenoFi offer a quick fix to this problem with our pre-approved ADU floor plans. Whether you want a single-bedroom, two-bedroom, attached, or converted ADU, we have just the right floor layout prepared for you.

What Are Some Additional Features of 400 Sq Ft ADU Floor Plans?

The best type of ADU floor plans for 400 sq ft are designed to promise balanced functionality and comfort within a limited area. The layout should be structured in a way that all essential rooms are well-defined and organized efficiently. Here are some additional features to look for in a floor plan that can help enhance the livability of any cozy 400 sq ft dwelling unit:

• Natural Lighting: The installation of large, expansive windows in the living room and bedroom is a great way to bring in natural light. This lighting provides an airy, bright atmosphere and enhances the sense of openness in tight spaces.
• Open Layout: An efficient, open-plan layout allows easy movement and interaction within the unit. It conveniently locates the dining, living, and kitchen areas adjacent to one another, allowing for seamless transition while cooking and serving meals. The design maximizes the available space and creates a comfortable living environment.
• Storage: Storage is a prevalent issue for occupants of ADUs measuring 400 sq ft or less. The inclusion of various storage containers, such as a bedroom wardrobe, kitchen shelves, and cabinets, helps keep the granny flat clutter-free, clean, and well-organized.
• Outdoor Deck: Construction of a small deck or patio is a great way to improve the comfort of the dwelling unit. It provides a space to unwind and enjoy the outdoor setting after a long day. This deck can be customized in a contemporary or traditional design to align with the theme of the main house and add visual appeal.
• Flooring: The type of flooring used in a separate accessory dwelling unit can elevate its functionality. Wooden flooring works best to add warmth and comfort to the common areas of the house. Meanwhile, tiled flooring in bathrooms and kitchens makes the space easy to clean and maintain regularly.

Funding Your New ADU

ADUs not only increase your home’s value after renovation - i.e. when the ADU has been built -  but can also generate rental income. However, ADUs are costly. If you don’t have enough equity in your current home, funding ADU construction with a home equity loan is impossible.

For example, let’s say your current home value is $500,000, and your outstanding mortgage balance is $400,000. You are planning on adding an ADU and expect the value of your home to increase to $640,000. Your current loan-to-value ratio (LTV) is already at 80%, which means that most home equity loans are out of reach because that’s the maximum LTV they allow. So, your borrowing power using your current equity is $0.

RenoFi, on the other hand, would allow you to go as high as 150% LTV of your current value or 90% of your after renovation value, whichever is lower. So, in this example, while using a standard home equity loan results in your borrowing power being $0, a RenoFi loan allows you to borrow up to $176,000 by using the after renovation value of your home!

Get started with your RenoFi loan here

Frequently Asked Questions (FAQs)

How big is a 400 sq ft ADU?

A 400 sq ft ADU is approximately the same size as a two-car garage. It usually has enough space for an open kitchen and living area, a single bedroom, and a full bathroom. The fewer walls there are, the more open space inside the unit there will be. Different variations of a 400 sq ft ADU plan, like a square or L-shaped design, offer differing space and yard distribution.

What is the best ADU size?

ADUs have varying size requirements across different states. They can be as little as 150 sq ft or as large as 1200 sq ft to accommodate large families. Generally, an accessory dwelling unit between 400 and 600 sq ft is sufficient for most situations. This size is ideal for serving as a guest house, rental unit, or home-based office without requiring an excessive lot of space and construction cost.

How much do ADU floor plans 400 sq ft cost?

The total cost of an ADU floor plan of 400 sq ft depends on multiple factors, including the location of the property, the permit fee involved, and foundation materials. Building an ADU floor plan of 400 sq ft can cost anywhere between $9000 and $30000 but is still cheaper than purchasing a single-family house or condo in most areas. The relatively low utility supplies and streamlined permitting also make these dwelling units a worthy and accessible addition.

How do you maximize space in a 400 sq ft ADU?

Various tricks and tips can give the illusion of greater space and openness in the unit. These include using multipurpose storage containers, fold-down tables, bookshelves, and hooks to organize your belongings efficiently. Big windows also play a huge role in making the smaller space feel much larger.

Conclusion

To conclude, despite their limited size, ADU floor plans of 400 sq ft are a comfortable and efficient living solution. These floor plans are designed thoughtfully to maximize the openness in the unit and make the most out of the benefits of an ADU for homeowners with smaller backyards. 

RenoFi loans are the most innovative way to finance a home renovation project. Unlike traditional loans, which are based on your current home value or require you to refinance your primary mortgage and give up your low rate, RenoFi loans are based on the after renovation value of your home. This allows you to borrow, on average, 11x more, get a low monthly payment, and keep your low rate on your first mortgage. 

Get started with our pre-approved ADU floor plans for 400 sq ft, which ease the permitting process and ensure that the ADU design of your dreams becomes a reality in no time!