Home sales in January fell through the floor, and housing experts say things will get worse for the industry before they get better.

Sales of new single-family homes dropped to an annual rate of 353,000 in January, 23 percent below the December figure of 457,000 and a35 percent decline from the year-earlier level of 539,000, the Commerce Department reported yesterday.

It was the second-lowest figure recorded since the department started collecting the data 20 years ago, with last September's figures the lowest. Sales had increased from October through December last year, before the January drop.

"This is a disaster for one month," said Michael Sumichrast, chief economist for the National Association of Home Builders. "I don't think it will get any better."

"This rules out a recovery in the first half" of 1982, he added.

Resales of homes in January fell to an annual rate of 1.82 million units, the lowest level in a decade and less than half the level 3 1/2 years ago, the National Association of Realtors had reported earlier. And Commerce also reported a decline in new-home starts last month.

Housing and banking industry officials have likened the current state of the housing market to the Depression, and are growing increasingly impatient with the Reagan administration's lack of assistance for the industry.

"The administration won't face it," said Thomas Harter, chief economist for the Mortgage Bankers Association. ".

The sales figures probably will drop again in March and April before moving up a bit in May and June, Harter predicted..

The inventory of unsold homes also rose, the Commerce report showed, and at the January sales rate it would take 9.3 months to sell the new houses currently on the market.

Sales prices of new homes edged down for the second straight month, from a median price of $68,600 in December to $68,000 in January.