Would You Include a Detached Casita in the Home's Square Footage?
Short answer: No.
A detached casita should not be included in the square footage of the main home. Instead, it should be identified separately so buyers can clearly understand what is included in the home's living area and what is additional finished space.
For example, if a property has:
1,800 SF main house
650 SF detached casita
The property should not simply be represented as a 2,450 SF home. The main home and casita should be shown separately.
But Doesn't the Casita Add Value?
Absolutely—it can.
A well-designed casita can be a valuable feature, particularly in markets where buyers place a premium on space for multigenerational living, guests, home offices, or other uses.
However, appraisers don't simply add the casita's square footage to the main home's living area and value all 2,450 square feet the same way.
What is GLA?
GLA, or Gross Living Area, is generally the finished, above-grade living area that is part of the primary dwelling.
Because a detached casita is physically separate from the main home, its square footage is reported separately rather than being included in the main home's GLA.
That does not mean the casita has no value.
Instead, an appraiser analyzes how the market reacts to that additional living space and makes an adjustment based on its contributory value. Depending on the market, that value may be significant—but it is not necessarily the same as the value assigned to an additional square foot within the main house.
Why Accurate Square Footage Matters
Accurately representing square footage is important for both the appraisal and the listing.
From an appraisal standpoint, the home's GLA is one of the characteristics used to compare the property to similar sales. If a detached casita is incorrectly included in the main home's square footage, the property may appear larger than it actually is when compared with other homes. This can make the comparison less meaningful and create confusion when the appraised square footage differs from the figure shown in the listing.
For listing agents, accurate square footage helps set clear expectations for buyers. Advertising a 1,800 SF home with a 650 SF detached casita as simply a 2,450 SF home could lead buyers to believe all 2,450 square feet are part of the primary residence.
Representing the spaces separately gives buyers a clearer understanding of the property while still highlighting the casita as a valuable feature:
Main home: 1,800 SF
Detached casita: 650 SF
The casita can absolutely add value—but accurately identifying it separately helps ensure the property's features, marketing, and eventual appraisal are all describing the property consistently.
What If the Casita Is Attached?
This is where things can become more complicated.
What if the casita was attached and you could access it from the main home?
There are generally two possible outcomes:
If the space is truly part of the main house and does not function as a separate living area, it may be included in the home's finished living area.
For example, a finished bedroom or guest suite that is connected to the home through direct interior access and functions as part of the primary residence would generally be included with the main home's living area, assuming it otherwise meets the applicable measurement requirements.
But what if it also has a separate entrance and a reasonable expectation of privacy from the main home?
For example, if the space has its own exterior entrance and is separated from the main home by a door that can be closed and locked, it may function as a separate living area rather than simply as part of the primary dwelling.
In that situation, the space may need to be reported separately rather than included in the main home's GLA—even though the two areas are physically attached. The specific layout, access, functionality, and characteristics of the space all matter.
The Bottom Line
A detached casita should not simply be added to the main home's square footage.
That doesn't mean it isn't valuable. In fact, a casita can be a significant selling feature.
The key is making sure buyers understand what they're getting:
Main home: 1,800 SF
Detached casita: 650 SF
Additional finished living space: 650 SF
Presenting the spaces separately creates a clearer picture of the property—and helps avoid confusion when the square footage reported in an appraisal differs from the number advertised in the listing.
And when you have questions about square footage or are worried that tax records may be incorrect, it’s best to get an accurate measurement of the home before listing it. After all, significant differences in living space can easily affect the value of a property.
Have a unique property or unusual living space you're unsure how to market? Reach out to Madison Block Appraisals before the listing goes live.
