About half of the Oahu property owners who get tax exemptions on their historic-designated homes are not complying with requirements. The City Council should approve legislation clarifying those requirements then vigilantly enforce them, sending a strong message that noncompliance will eliminate the tax break.

The owners of historic homes pay only $300 a year in property taxes, which is a great deal when considering that many of the dwellings are valued at $1 million or more. All they have to do now is to keep the house well-maintained and visible to the public.

Tall hedges, high walls or long driveways now keep many of the homes from being seen up close. One owner told the Star-Bulletin’s Rob Perez last September that his Round Top Drive home, which is not visible from Round Top, can be seen from miles away.

Of the roughly 250 historic homes given the exemption and reviewed recently in drive-by checks by city personnel, 28 lacked "reasonable visual access" by the public, according to Gary Kurokawa, administrator of the city’s Real Property Assessment Division.

A bill before the City Council would require that the entire front or rear of such a home be visible from a distance of no more than 50 feet from the property line.

Owners of historic homes lacking such close-up views may instead provide public access to "alternative visual visitation" from inside the property at least 12 days during the year, according to the bill.

Which dozen days are to be designated by the city director of budget and fiscal services, but the bill does not indicate how the public should go about learning what days they can pay such a visit. Such notice of public access should be part of the requirements.

Nearly half of the designated historic homes lack signs that are required to be posted informing passersby of the house’s designation.

Malama O Manoa, which does a fine job ensuring that the public can partake of the beauty of historic homes, will conduct its annual walking tour of seven open homes and 20 other historic homes and sites in Manoa Valley on May 1. However, the public is largely oblivious to historic houses elsewhere on the island.

The city has acknowledged that its oversight of the program has been inconsistent because of a shortage of staffing and training. The most effective method of dealing with that problem would be to increase training, of course, as well as the amount of property taxes to be paid by historic-home owners — enough to finance better oversight of the program without causing the owners to opt out.

We’re not convinced that adding three new staffers, as the Carlisle administration proposes, is necessary for enforcement.

Instead of laxity, vigilant random checks and low tolerance for noncompliance can be quite effective.

Related bills have been offered to the Council, one that would repeal and another that would change the tax exemption to a tax credit, good fodder for discussion.

The city forgoes about $900,000 yearly in property taxes because of this exemption, which aims to encourage preservation of historically or architecturally significant dwellings, an admirable goal.

But more is needed to assure compliance by participating homeowners — use the tax exemption rightly or lose it.