After waiting, they said, 10 fruitless weeks for their builder to resolve complaints about the construction of their new house in Burke Centre, Joseph and Yvonne Jennings reached a painful conclusion.

"Since (we moved in), we have had nothing but dissatisfaction and mental anbuish," they wrote Centex Homes of Washington Inc., the builder. "Our lifetime investment of $80,000 has been a hummer."

In the intervening seven and a half months, after a barrage of letters to Cntex and the Fairfax Consumer Affairs Office and a threatened trip to Centex's main offices in Dallas, the Jenningses have seen some of the problems corrected and promises made about some of the others.

As for the bowed roof in the garage, the last thing Joseph Jennings recalls is a shouting match between the contractor, the subcontractor and himself.

While the Jennings case may be unusual -- the list of alleged defects took 12 single-speced, typewritten pages to list -- there has been a dramatic doubling of complaints by other buyers of new houses in Fairfax County, according to a just-published county study that the Board of Supervisors will receive today.

?We have been inundated with complaints," Ronald B. Mallard, director of the county's Department of Consumer Affairs and one of the authors of the study, said in an interview.

The volume of criticism has increased so much. Mallard said, that complaints about housing construction are running ahead of the traditional number one consumer proglem in Fairfax -- automobiles.

The Fairfax study said that during the first five months of the current fiscal year, the consumer office received 229 complaints from buyers of new houses -- almost as many as the 252 received during all 12 months of the previous fiscal year. At that rate, the office predicted, complaints may rise by 118 percent by June 30, the end of the fiscal year.

There also has been an increase in the numbr f complaints to the countyhs Department of Evironmental Management, which is in charge of inspecting houses for possible violations of construction codes. While DEM has no figures for the cureent fiscal year -- which has seen an upsurege in building activity -- it handled 952 complaints in fiscal 1977 and an estimated 996 in fiscal 1978.

In fast-gtowing Fairfax, home construction has become a half-billion-dollar industry involving more than 200 builders. During the current fiscal year, more than 8,000 houses are expected to be built -- more than in Prince Georgehs County, Montgomery County and the District combined.

The most frequent compliaints to the fairfax consumber office, the study found, involved (in order of frequency) damp or wet basements, leaking roofs, inadequate insulation, poor drainage and landscaping and incomplete or poor painting.

Drainage was the biggest single source of complaints received at the inspection office. Ovrall, most of the complaints to DEM were in areas that are not covered by the various construction codes but by what the study called "good consturction practices or standards."

Not all houses get a uniformly thorough inspection, even though each must be awarded a occupancy certificate before someone can move into it. In the crush of heavy work loads, the sometimes understaffed inspection office must rely on spot check.

Complaints of poor workmanship and materials are not new in home constuction. But they have become even more common today, the studay said. Part of the blame was put on the upsurge in construction activity, during the time when there was a struction activity, during the time when there was a shortage of skilled help, from crpenters to superintendents. Also cited by the study were builders' eefforts to hold down costs, a shortage of quality materials and pressures to finish houses by promised deadlines.

Larry R. Coons, director of DEM, and one of the authors of the study, said he thought the biggest factor in the increase of complaints was heightened consumer awarness of what they had bought.

Robert Johnson, vice president of Northerm Virginia Builders Association, said, "I can't dismiss what Larry says," but added that workmanship, "in terms of cosmetics as opposed to code complaints, is a problem. We think iths a very severe problem. We're extremely concerned."

There are defects that are code violations -- such as improperly installed plumbing or electrical lines -- and others, not ocvered by ocdes, that are cosmetic -- such as ill-fitting doors or marred surfaces or finishes. Many of the Fairfax complaints were about cosmetic defects.

Johnson said the association has begun an inhouse apprentice program, and soon hopes to be graduating 200 carpenters, briklayers, electricans and foundation layers a year.

Johnson said the ranks of craftsmen in the Northern Virginia building industry were becimated by the recession of 1973-75, when many skilled workers, unable to find jobs, migrated to other areas of the country.

The fairfax school system has a small construction program under which vocational students get on-the-job training, but only 200 of the 45,416 junior and senior high school students re enrolled.