Housing, an industry that is seldom humdrum or predictable, once again is befuddling its most astute observers.

While the rest of the economy was turning slowly downward, housing starts edged up slightly in May. But the June gasoline crunch, still-mounting mortgage interest rates and a depletion of mortgage funds now have eroded some of the confidence of the nation's builders. They now are expecting starts to decline next year, and there are some real fears of a recession in the overall and resale housing markets.

Yet, it should be recalled that experienced observers had predicted a major downturn in housing starts last year. What happened? The 1978 starts topped 2 million, slightly highet than the total in 1977, which was an outstanding year for the production and sale of new housing. Resales also set records in both years, despite - or because - of an appreciation in housing values far beyond the general rate of U.S. inflation.

Now, after analyzing recent reports from builders across the nation, the National Association of Home Builders' chief economist Michael Sumichrast, is predicting that 1980 housing starts will drop below 1.6 million, which is the current projection for 1979 starts. Less than six weeks ago, Sumichrast and other housing economists still were predicting a substantial slump in 1979 housing starts and a mild rebound in 1980, which is a presidential election year.

Soundings taken in this area indicate that the potential market may have been nearly exhausted for new housing priced over $150,000.Conversely, demand continues to be heavy, not surprisingly, for both new and resale housing priced under $100,000. In fact, some builders are sold out months ahead of construction schedules that are being revised forward as the building pace fails to keep up with demand in the lower price ranges.

In terms of current prices, new house sales hereabouts are now averaging $90,700, compared to $68,500 a year ago. That's a 32 percent increase. Meanwhile, prices of existing house have increased 14 percent in the past year. On that basis, it is reasonable to assume that more home seekers are concentrating their efforts in the field of existing housing.

Statistics supplied by Sumichrast show that area residential building permits increased 2 percent above the 1978 level in the first five months of this year. All of the increase in in the multi-family housing sector. Permits for single houses are down 8.5 percent this year.

In terms of resales, which are esstential to the viability of new home sales (because three of every four buyers are previous owners), the evidence is that existing house sales are running 4.2 percent above those in 1978.

On balance, there is almost universal recognition that investments in residential housing are sound. That's because household formations are expected to increase during the 1980s, and the costs of new construction and financing - both now at all-time highs - are not expected to decline. Only the rate of increase is seen likely to moderate.

And even Sumichrast will tell you that a return to 10 percent mortgages is highly unlikely ever and that an upward turn to 14 percent would not surprise him.

However, Dr. Jack Carlson, the economist who is the newly installed executive of the National Association of Realtors, interpreted the May housing starts (up 5 percent over April to an annual rate of 1.8 million) as an indication that "housing will not suffer as it did during other economic slowdowns and should be expected to improve within the next 12 months." But he also conceded that resales, nationally in May, were slightly below the level of May, 1978, when the market truly was booming.

U.S. Home Corp., the nation's largest on-site manufacturer, reported last week that new orders decreased 9 percent from May 1978 to last month. But total orders for the first five months of 1979 were still 15 percent above that period last year, however.

Possibly those seemingly conflicting figures are truly indicative of the churlish housing market. It has been so good so long that slight downward movements and market inhibitions are subject to overreaction in interpretation.

Certainly, the public appetite for home ownership has not palled. It's only a matter of when and if the public's ability and confidence to absorb more ownership housing are overmatched by the total costs of handling that ownership.