The contractor’s truck sat outside the house next door for months.

Abigail Grossman and her husband first noticed it after buying their home in a Rock Creek Forest cul-de-sac in September. The couple quickly began renovations, as did their neighbor. In February, when they moved in, the truck still hadn’t budged.

“It was a little bit annoying,” Grossman said.

So she asked the neighbor to get the contractor to move it.

It was gone soon enough — towed away after rolling down the cul-de-sac and hitting a parked car.

The contractor may have gotten off easy. Under housing and zoning code changes that go into effect Monday, he might have been fined up to $500 a day for parking a large commercial vehicle in a residential neighborhood.

The new code, which also applies to large recreational vehicles, grew out of complaints from residents in Aspen Hill, Wheaton and Silver Spring about tractor-trailers parking on residential streets. Montgomery County Executive Isiah Leggett (D) set up a task force that recommended the change.

The restrictions don’t apply in Brookeville, Poolesville, Laytonsville, Rockville, Barnesville, Gaithersburg and Washington Grove, which raises the possibility of an enforcement loophole.

“Depending on how aggressively the law is pursued outside the city — we are right on the border, and just across the street is county jurisdiction — it could lead to those folks bringing their vehicles across the street into our neighborhood for storage,” said Eric Tublin of the North Farm neighborhood in Rockville.

Enforcement, however, is complaint-driven, and the permitting office has a manager and three inspectors to cover the entire county. Since Jan. 1, the permitting office has received 22 complaints about commercial trucks parked in residential areas, manager Susan Scala-Demby said.

The number of complaints is likely to rise with the mercury, Scala-Demby said, “especially in the summer, when people go outside and try to enjoy themselves. They see trucks and say, ‘It makes our neighborhood look trashy and poor.’ ”

Some small-business owners, especially self-employed contractors who park their vehicles at home, object to the code change, saying it raises the cost of doing business when many businesses are struggling to regain their footing in a weak economy.

“If they can’t park their vehicle, they have to get another vehicle or they have to pay to park it,” Peggy Moyers, the owner of a landscape business, said. The new code doesn’t affect her business because she has a warehouse where she can store her vehicles, but the restrictions would have if she were just starting. “It’s a hindrance on small companies trying to grow.”

Many of those small companies are run by immigrants, which may raise further complications, said former council member Mike Knapp, who introduced legislation to restrict parking of commercial vehicles in 2008.

“One question is, will any real ethnic discussion take place?” Knapp said. “That’s where more Latinos and Africans are getting their first commercial opportunity. That’s who you want to have in your neighborhood. They work hard. If they’re a single proprietor, that becomes a real challenge.”

The new code restricts commercial vehicles taller than eight feet, including any racks, and longer than 21 feet, including trailers, Scala-Demby said.

Another code change that goes into effect Monday limits the paving of front yards, a strategy some homeowners have resorted to in areas with scarce street parking.

Residents have objected to front yards being turned into big driveways, largely for aesthetic reasons.

Under the changes, homeowners can pave up to 320 square feet of their front yard, about enough space to park two cars. Yards paved before Oct. 26 are exempt.

Scala-Demby estimated that the permitting office received 10 to 15 complaints last year about front yards that had been turned into parking areas.