Summary: The county data has permits for home additions in the ZIP codes 20814, 20815, 20816 and 20817. These ZIP codes include Bethesda and Chevy Chase. We selected 815 of these permits.
The applicant gives the declared cost to the county before the work starts. The declared cost is the cost of the work. The declared cost can be different from the cost in a contract with a contractor. The cost in a contract can be higher or lower.
The median declared cost of these permits is USD 150,000. Half of the permits have a declared cost of not more than this number. The median area is 523 square feet (SF). For each permit, we calculated the declared cost for each SF. The median of these numbers is USD 242.
How we read the data
Montgomery County shows the data of its residential permits at its open data website. Each row of the data is one permit application. If the county gives a permit for the application, the row has the date of the permit. The row also has the date of the application, the work type, the work description, the area and the declared cost. The work description is the words that the applicant writes about the work.
The applicant gives the area and the declared cost to the county before the work starts. We read them as follows:
- The area is the space that the work adds or changes.
- The county gives the area as a number of square feet.
- For an addition, the area is not the area of the home.
- The declared cost is the cost of the work.
- The name of the declared cost in the county data is "Declared Valuation".
We selected the permit applications that have the work type "ADD" and the code "SINGLE FAMILY DWELLING". We selected only the applications with a date of the application from January 1, 2023. The data has 1,054 of these applications. The county gave a permit for 931 of them. We used 815 of these 931 permits. The other 116 permits have one or more of the items that follow:
- An area of less than 100 SF
- A declared cost of less than USD 20,000
- No number for the area
- No number for the declared cost.
The declared cost and the area of the 815 permits
The table that follows gives the declared cost of the 815 permits. The first row of the table shows that 25 percent of the permits have a declared cost of not more than USD 75,000.
| Share of the permits | Declared cost |
|---|---|
| 25 percent of the permits | not more than USD 75,000 |
| 50 percent of the permits (the median) | not more than USD 150,000 |
| 75 percent of the permits | not more than USD 300,000 |
| 90 percent of the permits | not more than USD 450,000 |
For each permit, we calculated the declared cost for each SF. The table that follows gives the declared cost for each SF.
| Share of the permits | Declared cost for each SF |
|---|---|
| 25 percent of the permits | not more than USD 143 |
| 50 percent of the permits (the median) | not more than USD 242 |
| 75 percent of the permits | not more than USD 397 |
| 90 percent of the permits | not more than USD 639 |
The table that follows gives the area of the addition.
| Share of the permits | Area |
|---|---|
| 25 percent of the permits | not more than 280 SF |
| 50 percent of the permits (the median) | not more than 523 SF |
| 75 percent of the permits | not more than 1,177 SF |
| 90 percent of the permits | not more than 2,138 SF |
The declared cost of small additions and large additions
The tables that follow give the median declared cost for five groups of additions. Each group has a different area.
| Area of the addition | Number of permits | Median declared cost |
|---|---|---|
| Less than 300 SF | 223 | USD 70,000 |
| Between 300 and 599 SF | 221 | USD 100,000 |
| Between 600 and 999 SF | 130 | USD 200,000 |
| Between 1,000 and 1,499 SF | 93 | USD 250,000 |
| A minimum of 1,500 SF | 148 | USD 350,000 |
| Area of the addition | Median declared cost for each SF |
|---|---|
| Less than 300 SF | USD 345 |
| Between 300 and 599 SF | USD 258 |
| Between 600 and 999 SF | USD 252 |
| Between 1,000 and 1,499 SF | USD 206 |
| A minimum of 1,500 SF | USD 150 |
The median declared cost for each SF is lower for larger additions. It is USD 345 for additions of less than 300 SF. It is USD 150 for additions of 1,500 SF or more.
Second-story additions and rear additions
We found the second-story additions with words in the work description (for example "second floor" or "two-story"). We found the rear additions with the word "rear". A permit in the group of rear additions has no word about a second story in the work description. The table that follows gives the median values of these two groups of permits.
| Value | Second-story additions | Rear additions |
|---|---|---|
| Number of permits | 267 | 152 |
| Median area | 1,036 SF | 430 SF |
| Median declared cost | USD 250,000 | USD 105,000 |
| Median declared cost for each SF | USD 244 | USD 251 |
Information that these numbers do not give
The numbers do not give this information:
- The items that the declared cost includes
- The cost in a contract with a contractor
- The type of the addition, if the work description does not give the type.
The permits have application dates in different years. Costs can increase each year. We used the declared costs that the applicants gave to the county. Thus, for the same work, the declared cost can be lower in 2023 than in 2026.
A work description can be incorrect, or it can have missing information.
Questions and answers
The declared cost of a home addition in Bethesda and Chevy Chase
The median declared cost of a home addition in these permits is USD 150,000. The median declared cost for each SF is USD 242. The cost in a contract can be different from the declared cost.
Is the median declared cost for each SF lower for larger additions?
Yes. In the data, the median declared cost for each SF is USD 345 for additions of less than 300 SF. It is USD 150 for additions of 1,500 SF or more.
The declared cost of a second-story addition
The median declared cost of a second-story addition is USD 250,000. The median area is 1,036 SF. We found 267 permits of this type.
Is the declared cost the cost in a contract?
Not always. The declared cost is the cost of the work. The declared cost can be different from the cost in a contract with a contractor.
How can you find the cost for your project?
The cost in a contract is different for each project. A contractor can give you a quote for your project.
Do you want an addition in Bethesda or Chevy Chase?
We can help you to schedule the work of your project. Request a Consultation.
Sources
- The source of the data is the dataset "Residential Permit" of Montgomery County open data (data.montgomerycountymd.gov).
- The data is for the permit applications that have the work type "ADD" and the code "SINGLE FAMILY DWELLING". The ZIP codes are 20814, 20815, 20816 and 20817. The dates of the applications are from January 1, 2023.
- We calculated each number from the county data with a script.
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