Putting an addition on a Montgomery County home is rarely just framing and drywall — the new square footage has to be fed from a panel that was often sized decades ago. David Williams Electric wires new rooms and additions across Bethesda, Rockville, Silver Spring and the rest of the county, starting with an honest load calculation so you know up front whether your existing service can carry the work. Thirty-plus years on the tools, Maryland license #11734, flat pricing before we start, and a 100% satisfaction guarantee.
Where the new circuits actually come from
A bedroom over the garage in Potomac, a finished sunroom in Olney, an in-law suite carved out of a Silver Spring basement — every one of them needs its own circuits: general lighting and receptacles, plus dedicated lines for anything that draws hard, like a mini-split, a bathroom, or a small kitchenette. The question is never whether we can wire it; it’s whether the existing panel has the room and the capacity to feed it.
We start every addition the same way: a real load calculation per NEC Article 220, not a guess. A lot of the housing stock here — the 1940s and ’50s capes in Chevy Chase and inner Bethesda, the mid-century ramblers around Rockville and Wheaton — still runs on a 100-amp service and a panel with no open spaces left. When the numbers say the addition will push you past what that service can carry, we tell you before the first wire goes in, and we price the panel or service upgrade as part of the job instead of springing it on you mid-project.
Built to Montgomery County's code and inspection
Electrical work on an addition is permitted and inspected through Montgomery County’s Department of Permitting Services in Rockville — the county runs its own process, separate from the statewide route some Maryland jurisdictions use. We pull the electrical permit under our own master license (MD #11734), wire to the current National Electrical Code, and schedule the rough-in and final inspections so the trade work lands in the right order with your framer, insulator and drywall crew.
That sequencing matters more than people expect. Miss the rough-in inspection before the walls close up and you’re opening finished drywall back up — an expensive, avoidable headache. We coordinate the rough-in so the inspector signs off while everything is still open, then come back for the final once the addition is buttoned up. You get a clean inspection record that holds up when you sell the house.
Newer homes have their own quirks
Not every Montgomery County addition is on an old service. The 1980s–2000s subdivisions in Gaithersburg, Germantown and the newer parts of Olney usually have 150- or 200-amp panels with capacity to spare — but they bring their own wrinkles: AFCI and GFCI protection requirements that have tightened since the house was built, and sometimes a finished-basement or sunroom bump-out where the original builder left no easy path to run new home-runs.
Whichever vintage your house is, you get the same thing from us: a written, flat price before we start, no hourly surprises, and a 100% satisfaction guarantee on the work. If something isn’t right, we make it right.
Frequently Asked Questions
Will my existing panel handle the addition, or do I need a service upgrade?
That's exactly what the load calculation answers, and it's the first thing we do. Many older Bethesda, Chevy Chase and Silver Spring homes still run a 100-amp service that's already close to full — a new bedroom or in-law suite can tip it over. Newer Gaithersburg and Germantown homes often have 200-amp panels with room to spare. We run the numbers per code, tell you straight, and quote the upgrade as part of the job if it's needed — never as a mid-project surprise.
Do you pull the permit, or is that on me or my general contractor?
We handle the electrical permit through Montgomery County's Department of Permitting Services in Rockville, under our own Maryland master license (#11734), and we meet the county inspector for the rough-in and final. You don't have to chase the county; we coordinate the inspections so they line up with your build schedule.
My addition has a mini-split and a small wet bar — does that change the wiring?
Yes. A mini-split and a kitchenette or wet bar each need their own dedicated circuits, and the wet bar receptacles need GFCI protection. We size those into the load calc from the start so the panel and the new circuits are right the first time, rather than discovering a shortfall after the drywall is up.
Can you time the wiring around my framer and drywall crew?
That's the part homeowners most often get burned on. The rough-in wiring and its inspection have to happen while the walls are still open — once drywall goes up, fixing a missed rough-in means cutting it back open. We schedule the rough-in to land after framing and before insulation/drywall, then return for the final once the addition is finished.
Which Montgomery County towns do you cover for addition wiring?
All of it — Rockville, Bethesda, Silver Spring, Gaithersburg, Germantown, Potomac and Olney, plus the surrounding neighborhoods. We're a local Maryland electrician, not a national franchise, so you're dealing with the same licensed crew from the load calc through the final inspection.
Serving Montgomery County
David Williams Electric provides home addition wiring throughout Montgomery County, including Rockville, Bethesda, Silver Spring, Gaithersburg, Germantown, Potomac, Olney. Explore all Montgomery County electrical services or learn more about home addition wiring across Maryland. Call (410) 781-4357 for a free, up-front quote.
