The District of Columbia Wage-Hour Board voted yesterday to increase the minimum wage for household maids and most other domestic workers in the city to $3.50 an hour, effective Feb. 4.

The new minimum will bring an 85-cent hourly wage increase from the current federal minimum wage of $2.65 an hour for most of the estimated 9,000 workers who are affected. The federal minimum will rise to $2.90 on Jan. 1.

For Washington maids, part of a group that traditionally has been near the bottom of the economic ladder, the board's unanimously adopted order will produce the highest government-set minimum wage for any group of workers in the United States. The highest current minimum is $3.15 an hour for all covered workers in Alaska.

In its order, the board said household help in Washington has become scarce, and that the higher wage should encourage more people to enter the occupation.

For fulltime babysitters, the board decided against ordering the same minimum wage as for maids, as had been proposed. Babysitters must be paid the new federal minimum of $2.90.

The $2.90 minimum also will apply, under the order, to casual yard workers, such as those hired to mow lawns or shovel snow. The board also approved a $3.10 minimum wage for people employed as companions to the aged and infirm.

The order requires a minimum of four hours' pay for any worker who goes to an employer's home, and a time-and-a-half pay rate for work beyond 40 hours a week.

It permits employers to deduct the value of meals served to workers, up to $1 for lunch or $3 for three meals a day, and the value of any lodgings that are furnished, up to a stated but flexible maximum.

Adoption of the order completed a process that began in March, when the board appointed a fact-finding committee. It recommended the $3.50 hourly pay as necessary to provide an adequate livelihood. A governmental reorganization delayed public hearings and the adoption of the order by about three months.

The D.C. Wage-Hour Board adopts minimum wages in nine different occupational fields. In most instances, where the D.C. minimum wage falls below the federal minimum wage, the federal level prevails.

Board members who adopted the new order were Paula L. Jewell, the chairman, and Joseph A. Beavers and David A. Wilmot.