Home additions are considered a significant home improvement as they provide additional living space within an existing home. Many homeowners desire such additions to meet their evolving needs, even if they already have a large house. Whether it’s an extra bedroom, a larger kitchen, or a spacious bathroom, home additions offer a solution.

There are various types of home additions available to address homeowners’ needs. These range from simple basement or attic expansions to extensive conventional additions that require substantial work.

Garage conversions can also be considered home additions since they add significant living space at once. Another popular option is a separate structure built apart from the main house, often referred to as a Detached Accessory Dwelling Unit (DADU). DADUs function as isolated dwelling units but are still classified as home additions.

The following outlines common types of home additions that can provide additional living space, along with important factors to consider when choosing the best option for your home.

Basement or Attic Conversion

A basement or attic conversion is an ideal option if you want to add living space without altering your home’s footprint. Technically, it may not be considered a traditional addition since it doesn’t expand the physical structure of the house.

However, transforming an existing attic or basement into a livable space is a practical and cost-effective way to increase your home’s square footage. Moreover, this type of project can add value to your property, allowing you to recoup your investment.

Before undertaking a basement or attic conversion, it’s important to ensure that certain structural requirements are met. The ceiling and floor structures, as well as the ceiling height, must comply with engineering standards to support the additional load of the living space.

Proper ventilation and insulation should be installed in the attic, and the basement must meet local building codes to ensure it remains dry. Attic conversions are suitable for homes without roof trusses, and conversions that include sleeping spaces must have egress exits, often achieved through the addition of special windows.

The average cost of completing an attic space is around $40,000, while a basement conversion may cost roughly half of that amount. However, costs can vary depending on the size of the space and the need for structural modifications. For example, the installation of new egress windows might be necessary.

Traditional Home Addition

A traditional home addition is an excellent choice for those looking to add multiple rooms to their existing house. This type of addition involves constructing a multi-room structure that is connected and open to the main house.

When well-designed, a home addition seamlessly integrates with the existing architecture, creating the impression of a cohesive and complete home.

A traditional home addition can include various types of spaces such as a dining room, bathroom, primary bedroom, great room, family room, or guest bedroom. However, it is uncommon for a kitchen to be included in the addition unless it is designed as a separate apartment suite.

Similar to building a new house, major home additions come with their own set of considerations and requirements. They are subject to permit regulations and building codes, and typically involve excavation, foundation work, and coordination with subcontractors for plumbing, electrical, and HVAC services.

When these additions are designed to include all the necessary elements for independent living, they are known as AADUs or Attached Accessory Dwelling Units. The average cost of a major home addition is around $72,000, but costs can rise to $150,000 or more depending on factors such as the use of high-end materials or a larger footprint for the addition.

Room Addition

A room addition is the ideal choice if you plan to add a single room to your home. This type of addition involves constructing a separate room attached to the side of the house.

Typically, a room addition serves a specific purpose, such as a bathroom or a bedroom. It is usually comparable in size to a standard room in the existing house.

A room addition can be designed to extend the kitchen, allowing for the addition of a kitchen island, or it can expand the dining area to create a more spacious and comfortable space for both dining and socializing. Room additions often feature a new roofline, which can be a flat roof or a shed style.

While a room addition is generally less expensive than a full-scale conventional addition, it is still a significant investment. It requires permits, adherence to building codes, and inspections.

Depending on the specific requirements, a room addition may also necessitate foundation work, adding to the overall cost of the project. It is not uncommon for a room addition to cost up to $50,000, considering the various factors involved.


A sunroom is an excellent addition if you desire a protected recreational space. It can be added to the side of your house and serves as an additional living area. Sunrooms are often designed with doors that can be closed off from the main house.

Compared to full-size additions, sunrooms are typically smaller in size and constructed using prefabricated materials, such as thermal-resistant glass and aluminum. These materials are assembled on-site. In some cases, sunrooms may be stick-built using concrete, lumber, and other materials that match the construction of the existing house, creating a seamlessly integrated living space.

It’s important to note that sunrooms are not intended for use as sleeping areas, and it is not possible to install a bathroom or kitchen in them. Since sunrooms are not meant to be permanent year-round living spaces, they offer certain features that may not be feasible in a traditional addition.

For example, sunrooms can include oversized glass panels that are difficult to incorporate into a conventional addition. Additionally, sunrooms generally do not require air conditioning or heating. However, building a professionally constructed sunroom can be an expensive undertaking.

On average, the cost can amount to around $30,000. Alternatively, DIY sunroom kits are available at a lower cost, typically around $5,000. If you possess the necessary DIY skills, this may be a viable option to consider.

Garage Conversion

A garage conversion can provide additional living space, making it an ideal option for in-law suites or other purposes. It offers a cost-effective solution for adding usable space to your home.

To convert a garage into a living area, you’ll typically need to install a ceiling, replace the garage door with a wall, and add suitable flooring.

Garage conversions can often be transformed into bedrooms or living rooms. In some cases, a garage conversion may include a kitchen and bathroom, functioning as an Accessory Dwelling Unit (ADU) or Attached Accessory Dwelling Unit (AADU). AADUs are sometimes constructed in conjunction with a new detached garage.

Casci Designworks Inc. provides professional home design services, including assistance with permits. For more information, please contact us at (916) 216-2786 or send us an email at sfcasci@gmail.com.