Summary: The data that we selected has 931 permits for home additions in the ZIP codes 20814, 20815, 20816 and 20817. These ZIP codes include Bethesda and Chevy Chase. The median time from the application to the permit is 41 days. The median is the middle value of the times.
The median time is longer for a larger addition. The median time is 31 days for an addition of less than 300 square feet (SF). The median time is 71 days for an addition of 1,500 SF or more.
How we read the data
Montgomery County shows the data of its residential permits on its open data website. Each row of the data is one application for a permit. When the county gives the permit, the row has the date of the permit. The row also has the work type and the floor area of the work in square feet. The applicant gives the floor area in the application.
We selected the applications that have the work type "ADD" (addition) and are for single-family homes. We selected the applications with a date of the application from January 1, 2023. The last application has the date October 7, 2026. The date when we read the data is October 8, 2026.
The time on this page is the number of days from the date of the application to the date of the permit. The county data shows that the work can start from the date of the permit. Before this date, the Department of Permitting Services (DPS) examined the plans and gave approval. DPS is a department of Montgomery County.
Only the applications with a permit have this time. The time can include days when the applicant corrects the plans. For example, DPS can examine the plans, and then the applicant can correct them.
The time from the application to the permit
The table that follows gives the longest time from the application to the permit for 25, 50, 75 and 90 percent of the 931 permits.
| Permits | Time from the application to the permit |
|---|---|
| 25 percent of the permits | not more than 26 days |
| 50 percent of the permits (the median) | not more than 41 days |
| 75 percent of the permits | not more than 70 days |
| 90 percent of the permits | not more than 118 days |
The table that follows gives the percent of the permits that have a time of not more than 17, 30, 60 or 120 days.
| Time from the application to the permit | Permits |
|---|---|
| Not more than 17 days | 12 percent |
| Not more than 30 days | 35 percent |
| Not more than 60 days | 69 percent |
| Not more than 120 days | 90 percent |
The code review time of the county
The county page for additions gives this information about the time:
- Some projects have the "intermediate track" procedure.
- For the other applications, the procedure is the "regular review process which may take up to 17 calendar days".
- DPS is "committed to completing code reviews within 17 days for adequately prepared applications".
- For some projects, the Washington Suburban Sanitary Commission (WSSC) must examine the application and give approval before the county gives the permit.
WSSC is not part of the county. In a code review, DPS examines the plans for the building codes. A code review is one step of the procedure for a permit. The time in the data is the time to the permit. This time includes the time for more steps than the code review.
Applications with no permit
The data that we selected has 1,054 applications. For 123 of these applications, the status is "Open" and the row has no date of the permit. For 66 of the 123 applications, the date of the application is more than 1 year before the date when we read the data. The data does not give the cause of the status "Open".
For the time to the permit, we selected only the applications with a permit. We also examined the 973 applications with a date of the application from January 1, 2023 to June 10, 2026. For these applications, the date of the application is 120 days or more before the date when we read the data.
For 82 percent of the 973 applications, the county gave a permit in 120 days or less. When we read the data, 9 percent of these applications had the status "Open".
The time for additions of different floor areas
The median time is different for additions of different floor areas. The table that follows gives the median time.
| Floor area of the work | Permits | Median time |
|---|---|---|
| Less than 300 SF | 254 | 31 days |
| 300 to 599 SF | 230 | 35 days |
| 600 to 999 SF | 131 | 42 days |
| 1,000 to 1,499 SF | 94 | 55 days |
| 1,500 SF or more | 149 | 71 days |
In the table, the median time is longer for a larger floor area. For 10 percent of the permits for additions of 1,500 SF or more, the time was 180 days or more.
The time for each year and each ZIP code
The table that follows gives the median time for each year of the application.
| Year of the application | Permits | Median time |
|---|---|---|
| 2023 | 287 | 44 days |
| 2024 | 232 | 36 days |
| 2025 | 246 | 45 days |
| 2026 | 166 | 36 days |
In the table, each year has only the applications with a permit. When we read the data, some applications of 2026 did not have a permit. Thus, the median time for 2026 can be too short.
The table that follows gives the median time for each ZIP code.
| ZIP code | Permits | Median time |
|---|---|---|
| 20814 | 149 | 42 days |
| 20815 | 266 | 39 days |
| 20816 | 182 | 36 days |
| 20817 | 334 | 44 days |
The median time is from 36 to 45 days for the years and from 36 to 44 days for the ZIP codes. For the floor areas of the additions, the median time is from 31 to 71 days.
After the permit: the time to the final inspection
The data that we selected has a date for the final inspection for 621 permits. This date shows that the work is completed and that DPS gave approval at the final inspection. For these permits, the median time from the permit to the final inspection is 204 days. For 25 percent of these permits, the time was 120 days or less. For 25 percent of these permits, the time was 327 days or more.
For this median time, we selected only the permits with a date for the final inspection. We did not select the permits with no date for the final inspection. For some of these permits, the work is in progress. Thus the median time for all permits can be longer.
Information that these numbers do not give
The numbers do not give this information:
- The time before the application
- The time for a permit from a town or village, for example in Chevy Chase Village
- The time for the Historic Area Work Permit (HAWP) in a historic area
- The cause of a long time from the application to the permit.
The owner and the designer prepare the plans before the application. For a home in a historic area, the owner must send the application for the HAWP before the application for the county permit.
Questions and answers
The time for an addition permit in Bethesda and Chevy Chase
For additions in Bethesda and Chevy Chase, the median time from the application to the permit is 41 days. The county gave 90 percent of the permits in 120 days or less.
Is the time shorter for a small addition than for a large addition?
Yes. The median time is 31 days for an addition of less than 300 SF. The median time is 71 days for an addition of 1,500 SF or more.
Does each application have a permit?
No. For 123 of the 1,054 applications, the status is "Open" and the row has no date of the permit. The data does not give the cause.
The time from the permit to the final inspection
The median time from the permit to the final inspection is 204 days. For this median time, we selected only the permits with a date for the final inspection.
Does a town or village add time to the procedure for a permit?
The county page for additions shows that a permit or other approval from a town or village can be necessary. This approval can add time. The county data does not show this time. You can contact the office of the town or village.
Do you want an addition in Bethesda or Chevy Chase?
We can help you to schedule the work of your project. Request a Consultation.
You can also read: Do I Need a Permit for a Home Addition in Montgomery County, MD, in 2026?
Sources
- The source of the data is the dataset "Residential Permit" of the open data of Montgomery County (data.montgomerycountymd.gov). The date when we read the data is October 8, 2026.
- The data is for the applications with the work type "ADD" (addition) and for single-family homes in the ZIP codes 20814 to 20817. The dates of the applications are from January 1, 2023 to October 7, 2026.
- The source of the information about the code reviews is the county page Residential Additions Permit Process. The date when we read the page is October 8, 2026.
- The source of the example of Chevy Chase Village is the page Building Permit Application of the Village. The date when we read the page is October 8, 2026.
- We used a script to calculate the numbers from the county data.
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