THE FAIRFAX COUNTY real-estate disclosure ordinance just enacted requires that the sellers of new houses in the county provide would-be buyers with information about restrictive covenants, utilities, insulation, schools, sewer lines and other essentials. Those who don't provide the information can be fined up to $500. This is apparently the first ordinance of its kind in the Washington area. It should not be the last. Every buyer of a house anywhere ought to receive the kind of information the Fairfax Board of Supervisors has now voted to require that some buyers receive.

The new ordinance is a good start toward solving an old problem. But its coverage should be expanded in Fairfax County to include old as well as new houses -- and versions of it should be adopted by other area governments. The usefulness of the designated information to people buying houses is so obvious you would think no one would buy a house without having got it. But Fairfax officials say this is not so. They are now receiving more complaints from buyers of new houses about broken promises or faulty information than they are from buyers of automobiles -- an almost unheard-of situation in local government. The real-estate purchasers say they have not been told about such things as homeowners' association dues and adjacent commercial zoning.

While such information is clearly relevant to a decision to buy a particular house, disclosure of it may make selling that same house more difficult. Although the house builders and the real-estate agents in Northern Virginia insist this kind of information is supplied routinely to prospective buyers, they fought adoption of the Fairfax ordinance bitterly. Their opposition, climaxed by a misleading newspaper advertisement, may have turned a close vote on the Board of Supervisors into a unanimous one. If it did, they got what they deserved. The real-estate market is so structured in this area that the buyer of a house is almost always at a disadvantage. The new ordinance will at least give some buyers some protection against the misleading quick deals that too often go bad.