Honolulu’s older residential areas are dotted with so-called monster houses, in part, because city codes have not effectively fended against this uglification trend, which brings with it potential troubles ranging from overburdened neighborhood parking to stressed infrastructure.

But with the City Council approving a measure that limits maximum density for detached dwellings, there’s reason to be optimistic that there soon could be a halt to construction of hulking structures that leave scant room for yards or anything else on their lots — and are used as illegal rentals, vacation homes and other nonconforming businesses.

Under Bill 79 (2018), homes cannot have a floor area ratio (FAR) exceeding 0.7, meaning a floor area greater than 70% of a house’s lot size. Houses with FAR greater than 0.6 would need to be owner-occupied and meet additional rules. Those rules include side and rear yards of 8 feet and temporary certificates of occupancy that allow city officials to inspect the property.

That’s an improvement over the city’s history of approving even suspicious home construction and conversion plans because bureaucratic hands were tied by regulations that did not set limits on the number of bedrooms or wet bars (a serving counter fitted with a sink and running water) allowed in residential districts.

One 18-bedroom house in Kalihi — described in building permit paperwork as a two-story, single-family dwelling with a wet bar — stands as a glaring example of an intrusive monster.

Honolulu’s land-use ordinance allows one- and two-family detached dwelling units on lots in residential areas. Neighborhoods should not have to put up with multifamily structures better suited for an apartment district, or a new zoning class.

It’s true that not all monster construction is undertaken by parasitic developers or lot owners looking to make money while dodging the law. In some cases, property owners have legally replaced single-family homes with significantly larger structures to accommodate multiple generations of an extended family.

With a shortage of affordable housing figuring prominently among Oahu’s high-cost-of-living issues, such an arrangement is not surprising. However, city law limits property owners to housing no more than five unrelated people on a property, and no more than three unrelated people if the owner’s own family lives on-site. To retain a neighborhood’s sense of character, that limit should be respected.

Also among the bill’s provisions: Converting or altering a wet bar, laundry room or bathroom is prohibited unless specifically allowed under a valid building permit; and construction beyond the 2,500 square-foot mark requires reserving more on-site space for parking. If tenaciously enforced, both restrictions could help put a dent in monster-house creep.

In addition, under the measure, a limit of 75% of a property can be covered with an impervious surface, such as concrete or asphalt.

Supporters of this requirement, including The Outdoor Circle’s Manoa branch, persuasively pointed out in written testimony that the surface of at least one-quarter of a lot — preferably more — should be absorbing or porous, thereby making room for trees and other greenery as well as more percolation of stormwater runoff down to the water table.

Besides serving as a guard against flooding, the impervious surface limit holds potential to block further spread of an unsightly concrete-jungle aesthetic on long-established single-family home streets.

Mayor Kirk Caldwell should sign Bill 79, which the Council passed unanimously last week. And the city should see to it that enforcement efforts are stepped up. With more housing rules on the books, more vigilance will be needed to flag suspected scofflaws.