The Short Answer
In most cases, no. If you’re replacing old windows with new ones that fit the same opening, Montgomery County generally does not require a building permit. The county’s Department of Permitting Services (DPS) lists windows and doors as work that needs no permit, as long as the opening size and the net clear opening dimensions stay the same.
Most window replacement projects in Montgomery County fall into this category. But there are a few important exceptions every homeowner should know before work begins.
When You Do Need a Permit
You will likely need a county building permit if your project includes:
- Making a window opening larger or smaller. This changes the wall framing.
- Adding a new window where there wasn’t one before.
- Moving a window to a different spot on the wall.
- Structural changes, such as replacing a header or altering load-bearing framing.
- Converting a window to a door, for example adding a patio door where a window used to be.
When framing changes, the county wants to make sure the wall can still safely carry the load above it. That’s why these projects go through permit review and inspection.
What Is a “Net Clear Opening,” and Why Does It Matter?
The net clear opening is the actual open space you can climb through when a window is fully open. It’s not the same as the window’s overall size.
This matters most in bedrooms. Building codes require bedroom windows to work as an emergency exit (egress), with a minimum opening size. If you swap a window for a different style, such as a double-hung for a casement or a slider, the clear opening can change even if the frame size stays the same. If the new window makes that opening smaller, it may no longer meet egress requirements, and a permit may be needed.
A good installer checks this before ordering windows, so your new windows meet code from day one.
Cities With Their Own Rules
Montgomery County DPS handles permits for most of the county, but some incorporated cities and towns have their own building departments and rules. Gaithersburg and Rockville, for example, have their own permit offices. If your home is inside city limits, check with that city as well as the county.
Historic Districts
If your home is a designated historic site or sits in a historic district, the rules are stricter. Exterior changes, including window replacement, may need a Historic Area Work Permit (HAWP) from the Montgomery County Historic Preservation Commission. This can apply even to same-size replacements, because the look and materials of historic windows are protected.
Don’t Forget Your HOA
A county permit and HOA approval are two separate things. Even when the county doesn’t require a permit, your homeowners association may still need to approve the style, color or grid pattern of your new windows. We cover this in detail in our guide: Do You Need HOA Approval to Replace Windows or Doors in Maryland? Here’s what one homeowner in a Montgomery County townhouse community said about working with us:
All Dwelling Solutions were knowledgeable regarding their product and the installation was professional and timely. I would definitely recommend this window company to other residents in my town house community/HOA
What Happens If You Skip a Required Permit?
Doing permit-required work without one can lead to stop-work orders, re-inspection fees and trouble when you sell your home. Unpermitted structural changes can show up during a buyer’s inspection and delay or complicate the sale. It’s always easier to get it right at the start.
How All Dwelling Solutions Helps
Before any project begins, our team reviews the scope of work and lets you know whether a permit, city approval or historic review may be needed. Most of our window replacements are same-size installations that fit the existing openings, so they move quickly without permit delays. When a permit is required, we explain what’s involved up front, with no surprises.
All Dwelling Solutions is a licensed and insured window and door company serving homeowners in Rockville, Bethesda, Potomac, Gaithersburg, Germantown, Olney, Silver Spring and throughout Montgomery and Howard counties.
Visit our North Bethesda showroom to see windows and doors in person, or request a free in-home estimate today.
Permit rules can change. For the most current requirements, contact Montgomery County DPS by calling 311 or visiting the DPS website.
