More frightful than a Halloween ghoul, “monster houses” are popping up in Honolulu and striking fear into already hemmed-in neighborhoods, with potential troubles tied to the jumbo-sized dwellings ranging from clogged traffic flow to stressed infrastructure.

The City Council must act quickly to curb this trend in which property owners are replacing single-family homes with significantly larger structures that could accommodate several families. The proliferation is especially irksome in older residential areas where in some cases such houses include upwards of 20 bedrooms and several kitchens. They appear to be intended for use as multifamily dwellings, which is a violation of the city’s Land Use Ordinance. Among the most questionable cases: a property on Houghtailing Street, which reportedly has more than two dozen bedrooms.

More exasperating than brazen property owners is the city Department of Planning and Permitting’s practice of approving suspicious home conversion plans because its bureaucratic hands are tied by zoning regulations that do not set limits on the count of bedrooms or wet bars (a serving counter fitted with a sink and running water) allowed in residential districts.

Current zoning allows one- and two-family detached dwelling units in residential areas. Properties with three of more units are tagged as “multifamily” and designated for apartment districts, which allow walk-ups and high-rises. In cases where DPP determines that land-use violations have occurred, it issues citations. Even so, the monster-house trend is growing, and threatening to adversely alter the character of neighborhoods.

When reviewing building plans, DPP flags the eyebrow-raisers and requires property owners to file an affidavit or restrictive covenant stating that the permitted use will be adhered to — no altering of plans for other uses. In some cases, though, neighbors maintain that the monster houses are being used on the sly as illegal short-term vacation rentals.

More than likely, some property owners are finger-crossing behind their backs. But even in cases where the units are packed with legit extended family members, there should be at least a gauged occupancy limit for each property on a residential street. Two dozen bedrooms at a single address could mean two dozen cars vying for street parking, for example. Other potential headaches include strains on sewer lines and storm runoff apparatus — not to mention fire-safety conditions being up to code with so many people under one housing roof.

Two bills slated to get their first airing at today’s Council meeting should be supported, as they’re designed to help subdue, if not slay, the monster-house problem:

>> Bill 94 places a moratorium on all large-scale homes in residential neighborhoods until city officials can evaluate the matter and put in place effective permanent regulatory controls.

>> Bill 100 creates a “high-density residential” real property tax category that singles out monster houses from other residential properties for a new tax category that pays a higher levy than single-family properties. The bill aims to prevent newly built, higher-priced monster houses from touching off higher assessments for nearby residences. Some of those property owners are rightly concerned that they could otherwise be priced out of their longtime neighborhoods.

Also, last month Councilman Trevor Ozawa introduced a proposal that calls for Honolulu Hale to set much-needed limits on the number of bedrooms and wet bars allowed in single-family homes, and more stringent off-street parking requirements.

What’s more, property owners seeking building permits for a large count of bedrooms or wet bars should also go before the Council for scrutiny and approval, and bring affidavits stating that the homes will heed designated zoning.

Ozawa has said the city ought to address the monster-house problem “on the front end rather than on the back end — before the house is built.” He’s right. Tougher and more precise policy is needed. And in cases where property owners persist in deception, rather than allowing them to make amends by paying a citation fine, they should be required to swiftly conform to the city’s land-use ordinance or tear down the structure.