Ultimate Guide To Home Additions In Orange County

If you own a property in Orange County or Southern California and need additional space, one option is to purchase a larger home. Alternatively, you might build an addition to your current home to offer additional living space. One- or two-story home additions are excellent ways to enhance your home’s enjoyment and raise its resale value.

home addition general

Here at GreatBuildz, we speak with clients every day who are considering a home addition project. GreatBuildz is a free service that connects homeowners with reliable, pre-screened home addition contractors, then provides ongoing project support to ensure a stress-free experience.


In this blog, we’ll share some ideas, costs, and tips about adding different types of additions to your home and finding the best contractors for your project.

Looking to Construct an Addition to Your Home? What To Know Before You Begin 

Room Addition and Extension Concepts

Kitchen expansions and additions:

kitchen home addition

Many homeowners consider the kitchen to be the center of their home. However, in many older homes, the kitchen is small and closed off – this is quite typical of the modest Orange County homes built before 1980. Therefore, many people are deciding to increase the size of their kitchens in order to accommodate the current trend of large, open kitchens for hosting social gatherings.

By constructing a kitchen addition or expansion, you can create a spacious, attractive area with room for an island or walk-in pantry. You will likely require the assistance of an architect or designer to produce a home addition plan for a functional new kitchen layout.

Bathroom additions:

As it is fairly common for older homes to have a limited number of bathrooms, a bathroom addition is a common home improvement project. In addition to resolving the practical issue of too many people sharing too few bathrooms, adding a bathroom to your property can significantly increase its resale value. Many homeowners and homebuyers want enough bathrooms so that adults, children, and guests do not have to share.

Bathroom renovations can be as basic as adding a powder room for guests or as extensive as constructing a luxurious master bathroom. Due to the necessity of running water and waste lines, the average cost of a bathroom will always exceed that of a bedroom.

Addition of a bedroom or home office :

home addition home office

Numerous homeowners in Orange County and Southern California find that their family has outgrown the number of bedrooms in their home. If they do not wish to relocate, they can easily add more space to their current residence. Adding one or more bedrooms will increase the home’s functionality and market value.

A bedroom can also serve as a home office, guest room, or for other purposes. Any such space should ideally be designed with a closet so that future buyers will be ready to pay more for the additional bedrooms. Unlike a bathroom or kitchen, this is the simplest and least expensive of all home additions to construct because water and waste lines are not required.

Master bedroom suite addition:

home addition master bedroom

Numerous older homes were constructed without a master bedroom space. Therefore, adults may have to share a bathroom with children (not fun).

Despite the fact that this was the case many years ago, many homeowners today desire a master bedroom suite with its own elegant, private bathroom and walk-in closet. The master suite addition is therefore a popular home renovation project, despite the fact that its size may result in a hefty price tag. People will occasionally add a second floor to accommodate a private master suite.

Above a garage:

Occasionally, it is possible to add room to an existing part of your residence. Depending on the location of your garage, it may be possible to construct a living area above it. Creating an addition above a detached garage is commonly referred to as a granny flat or Accessory Dwelling Unit, which has become quite popular in California following recent legislative reforms.

Although the first-floor garage structure may need to be reinforced or “braced” to accommodate the additional weight of the second story, this additional living space can be built without sacrificing any of your lot area.

Attach an ADU:

With the new ADU regulations in California, an increasing number of homeowners are opting for these types of home additions. An attached accessory dwelling unit (ADU) is essentially a second home or full living unit that is attached to the primary residence. It had a separate entrance and all the amenities of a small house, including a kitchen, bathroom, and sleeping area.

ADUs range in size from 250 to 1,200 square feet. They can be utilized for a variety of purposes, including housing families, seniors, and children over post-college, or as rental properties to generate additional income.

Other Home Additions – living room, family room, or bonus room:

Similar to adding a bedroom, installing a living room or family room is less expensive than adding a bathroom because it does not require water or waste lines. These types of rooms consist primarily of four walls and a roof. In these areas, you will still need to consider aesthetic elements like lighting, built-in cabinetry, and HVAC vents.

Because these sorts of rooms come in a wide range of sizes, it is essential to conduct research on the ideal size for your intended use. You don’t want to have a room that is disproportionately large or small relative to the rest of the house.

living room home addition

What is the cost of a house addition?

Typical home additions will cost somewhere between $200 and $400 per square foot.

Depending on what you want to do to your property, home additions can vary significantly. They can range from a modest bathroom addition to a complete second-story addition. Let me describe the most common types of home additions and their average costs. Please keep in mind that building expenses vary substantially by geographical region, thus the costs below apply only to remodels in Orange County and Southern California.

Costs for Adding a Master Suite

In Orange County, the cost of a master suite addition will range from $120,000 to $200,000.

Common average costs and a decent starting budget is $150,000. A master suite floor plan can be as small as 300 square feet, although most additions are between 400 and 500 square feet or greater. A popular size for a master suite addition is 20×20 or 20×25 feet, but it can be any size. The prices for a complete guest suite and an in-law suite are comparable. This cost is based on a one-story addition.

Costs of a Bathroom Addition

home addition bathroom

A bathroom addition to an existing home will cost between $50,000 and $100,000.

The cost of a new bathroom will vary according to its size and amenities. Obviously, a half-bath with just a toilet and sink will cost less than a complete bathroom with a tub or shower. A luxury master bathroom will involve the greatest expense. The average cost will also depend on the exact location of your addition and its proximity to the nearest plumbing connections, etc.

How much does it cost to add a kitchen?

home addition kitchen

An average kitchen addition will cost between $80,000 and $120,000.

A kitchen addition is actually a kitchen enlargement or relocation, but it still involves demolishing the old room and creating a new kitchen in the additional or expanded space. Because of cabinetry, countertops, and appliances, a kitchen is usually an expensive space to redesign on its own. In addition, a kitchen addition or expansion involves running new plumbing, electrical, and gas systems, etc.

Related: Orange County Kitchen Remodel Costs and Tips

Cost of a Bedroom Addition

home addition bedroom

A room addition should cost between $30,000 and $60,000 and is the simplest room to build.

This room addition is the least expensive because it does not require plumbing or gas connections (it is a dry room). Obviously, the cost will be proportional to the size and will increase if you include other features such as built-in cabinetry, closet cabinetry, etc.

Price of a Second-Level Addition

A second-story addition will cost at least $100/sf more than a conventional single-story addition, ranging between $400 and $500 per square foot on average.

A second-story addition will always be more expensive due to the additional construction necessary to sustain the added weight. This may involve strengthening the home’s foundation, adding structural support to the walls and structure of the first floor, installing beams, etc.

Other significant expenses include removing the roof from the first level and re-roofing the new rooms on the second floor. In addition, you will need to construct a new staircase leading to the second level and possibly reconfigure the electrical, plumbing, and HVAC systems. The majority of people discover that they must reconfigure some of the first-floor plan in order to fit the staircase and second-story area.

Please keep in mind that while you can begin your budgeting research with the above basic pricing figures, the best method to obtain genuine, accurate cost estimates is to discuss your project and/or plans with a few reputable general contractors.

How should one begin planning their home additions?

planning home addition

Once you have a general concept of the cost and budget for the home addition you wish to build, the next step is to begin planning the options. After conducting research, you will need to make some broad decisions regarding the size and location of the future room you want to add to your home.

Consider how the area will function for you now and in the future, as well as how valuable it will be to a future buyer of your home. If the room addition is useful and well-constructed, it will greatly increase the resale value of your home. However, you should not build a home that is ‘overbuilt’ for the area in terms of size or number of bedrooms.

You will need to understand the zoning regulations in your area and evaluate whether you have sufficient space on your property to construct the desired addition. There are two solid approaches to finding out your options for a room addition.

First, you can visit the city’s building department and request assistance with zoning and regulations. Alternatively, you might contact a local architect or designer and request that they visit your home to assess the possibility of constructing a home addition. A reputable local contractor may also help guide your decisions at this early stage and provide you with cost estimates based on their recent work.

You should also consider if you will be able to continue living in your home throughout construction. If the additional space is separate from your primary residence, you may be able to live at home. However, a major or second-story addition would make it difficult or impossible to remain in the house. Undertaking a large renovation could be disruptive to your lifestyle, therefore it is prudent to set living arrangements in advance.

Considerations When Planning a One-Story Addition

One-Story House Extension

When planning to build a one-story addition to your home, the most likely locations are the backyard or the front yard (usually not enough room on the side). That means you must have space in your front or back yard to construct the addition. In addition, most municipalities mandate a ‘setback’ from your front or rear property line (an area you cannot build). Therefore, the first step is to determine if you have enough space in your yard to create the needed additional living area.

Determining how this new addition room will “connect” to the rest of the house is also crucial. You want the layout of your expanded home to be practical and easy to navigate. You do not want odd connections between rooms, such as building a bedroom adjacent to the kitchen. Early in the process, you’ll need to hire an architect to draw your existing home’s layout on a simple plan and then evaluate how an addition could link to it.

It is possible that portions of your current home will need to be altered in order to suit your proposed addition. Keep this in mind while creating a budget… Any reorganization of your current home’s layout will involve additional costs.

Considerations When Planning a Second-Story Addition

two story home addition

When planning for a second-story addition, it is essential to choose a qualified architect. The architect will also need to consult with a structural engineer to assess the requirements for bracing the first level to accommodate the additional weight. A competent architect will collaborate with you to create a home addition that allows a staircase on the first floor while maintaining the practical layout of the first level.

A second-story addition is a substantial undertaking that will consume a considerable amount of time and make it difficult for you to remain in your home during construction. First, the contractor will need to remove a part of your roof and perform substantial work on the first floor. After the framing and roof have been installed, it may be easier to live in the house during construction.

What is the procedure for constructing a home addition?

home addition procedure

Once you’ve decided to pursue a home addition, it’s a good idea to consult with architects and contractors to find the best fit. Occasionally, you may wish to begin by interviewing contractors, and the one you choose can bring an architect with whom they have a relationship.

It is not recommended to begin by just hiring an architect to design your home addition. When the designs are finalized, it is possible that the construction quotes you receive from contractors will be higher than your budget. If this is the case, you will need to revise your plans to fit within your budget.

Engage a minimum of one contractor throughout the entire plan design process in order to keep your house addition’s prices reasonable or affordable. I would not recommend relying on an online home addition cost calculator because each project is unique and costs vary substantially based on location.

A Few Home Addition Guidelines Before You Begin

Costs for Home Addition Permits

Don’t forget to budget for the city plan review, permit, and any other impact fees that your city will impose to permit this construction.

Always include 10-20% contingency in your budget in excess of the contractor’s estimate. You may be pleasantly pleased if you do not utilize it. In the majority of cases, though, you may encounter unanticipated expenses that will add to your budget.

Less changes will be required during construction if the project’s scope and materials are outlined in greater detail beforehand. And modifications are always costly and entail delays.

When the project is complete, remember to add this additional room to your homeowner’s insurance policy. Also, inform your insurance agent as you begin building to ensure that you are protected against any possible risks.

How may a home extension be financed?

finance home addition

Some people have saved enough money to pay for an addition out of their own savings or investment accounts, but the average cost of an addition is so large that you may need to seek financing. When searching for a home improvement loan for an addition, there are several options to consider. The financial alternatives for remodeling include construction loans, rehabilitation loans, refinancing, and others. Check out our blog on renovation financing for information on the many lending alternatives available.

How can I locate a local home addition contractor?

home addition contractor

A general contractor is the only type of contractor qualified to construct a home addition. No other contractor is licensed or qualified to perform this complex building work. And you should never consider using an unlicensed or uninsured contractor to do your home addition.

The easiest approach to finding a reliable general contractor is to ask friends and family for referrals of someone they have previously worked with. If your contact had a positive experience with a general contractor, you can be reasonably confident that you will also receive quality service. If you are unable to obtain a strong referral from friends or family, our staff at GreatBuildz can connect you with a few trustworthy local general contractors who can construct a home addition in your area.

When it comes to planning and coordinating home additions on your property, you shouldn’t have to go it alone – GreatBuildz can help simplify your renovation experience.


GreatBuildz is a free service that connects homeowners with reliable, thoroughly screened general contractors and provides project support from start to finish. Call now (818.317.3567) to chat with a real person about your next renovation project or visit our website for more information: www.greatbuildz.com.

Hi, we're Paul and Jon - Co-Founders of GreatBuildz. We believe everyone deserves to find a great contractor, have a stress-free renovation, and enjoy their beautiful new space. There are so many contractors out there and it's often hard to tell the good from the bad... until it's too late. We started our company to help simplify your contractor search and help you have a stress-free renovation experience. We're always available to help, no matter where you are in the process. Click here to learn more about our story.

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