The Montgomery County Board of Realtors ordinance requiring property sellers or their agents to furnish buyers with copies of local land use plans affecting the property.

The board, which says it is opposed to the ordinance in part because it is more stringent than a similar one covering the county, has intervened in a suit filed March 16 by Rockville realtors John Dennis, Robert E.Montgomery and Waddell S.Taylor. The board has asked the Montgomery COunty Circuit Court to declare the ordinance unconstitutional. The ordinance is scheduled to go into effect next Friday.

It requires the seller or agent to provide the buyer of commercial or residential property with maps showing planned uses, roads and highways, and the location and nature of the proposed parks and other public facilities affecting the property. If the seller does not comply, a purchaser may cancel the contract any time before settlement.

The Board of Realtors is afraid the ordinance may impede business by slowing down the signing of contracts. The Rockville City Hall, where the city's master plan is on file, is not open nights and weekends when many deals are closed, the board said. A seller who is ignorant of the requirement could lose a costly contract, the board added.

Moreover, the realtor group contends that the master plan may be too difficult for the parties to understand. And finally, it alleges that the ordinances is unconstitutional because it "seriously interferes with the rights of parties to contract" - a right guaranteed by the state and federal constitutiions.

Two and a half years ago Montgomery County passed a similar ordinance - with certain important differences. The seller or agent was simply required to tell the buyer of the existence and location of such a plan and the buyer's right to examine it. The buyer had the option of waiving his right to see the plan.

In practice, the standard contract used in the county contains the waiver, so by signing the contract, the buyer also waives his or her right to the plan. According to Assistat County attorney Carol jeffries, a seller or agent is only obligated to tell the buyer about the plan, not what it contains. SO, if the sale is consummated and the buyer later finds a highway is scheduled to be built through his back-yard, the seller cannot be held liable.

The board of realtors says only one such case has been reported to it since the ordinance went into effect. In that case, the board said, the new owner found out after settlement a public park was to be built opposite his house; the agent had not known about the park. The board declined to say what, if any, action it took or whether any legal action was taken by the buyer.

The Montgomery County ordinance never applied in Rockville, which has its own master plan. However, the city Council and the major'soffice have been receiving complaints for some time that buyers were not apprised of future building plans. A dozen complaints were heard last year alone.

So City Councilwoman Phyllis Fordham brought up abill to solve the problem.