A house can be contructed - the site leveled, the foundation poured, the boards nailed together - in 75 days or less, builders claim. But the paperwork that precedes the bulldozers and continues while the nails are being puonded consumes far more time.

In Fairfax County, the entire subdivision development process, from rezoning to issuance of a residency permit, took annaverage of 199 weeks for projects completed in 1976.

The builders complained that that was too long.While they waited for myriad approvals from various county offices, they said, interest charges on idle land mounted, along with other costs. In the end, they said, the home buyers paid the price of the delays.

After hearing the complaints for years, the county government recently began making changes to speed up the process, and officials now estimate they have reduced the 199-week period to 162 weeks. In addtion to the 14 speedups already in effect, the county plans to implement four others, although their impact on the time period is expected to be "minimal."

Among the changes:

A new flow chart is given to developers to help guide them through the process without major stumbles.

Where plans were once reviewed with a dozen or more agencies meet clloectively with the developer.

Agencies that review preliminary plans now finish their work in 30 days instead of up to 60 days.

Plan reviews are now coordinated to better control the work done by many agencies on one project and expedite it.

The fire marshall, the Fairfax County Water Authority, and the Health Department now review plans earlier to avoid delays caused when revisions have to be made later in the process.

Construction plans are now reviewed even before the previous step - approval of the site or subdivision plan - is completed.

While many of the speedups involve changes within the county's extensive review process, Mary Elizabeth Holbein, director of the Office of Research and Statistics, said in a memo to County Executive Leonard Whorton: "The . . . more significant elementsof the processing time (approximately two-thirds of the total processing time) is that time required by developers to comply with provisions of the county ordinances and staff recommendations and the time which elapses (while the building is actually being constructed). A strong rela tionship exists between the housing market conditions and the diligence with which developers pursue the development process."

In so many words, Holbein was saying that if houses are selling well, the developer will have an incentive to do the work quickly and correctly.

Several weeeks ago the Fairfax Board of Supervisors adopted staff proposals to trim a year from the development process for business and industries.

Among the time-savers adopted: accelerated consideration of amendments to the master plan; out-of-order hearings on rezoning requests; site plan review before the previous step rezoning hearing - is completed; provision of a county ombundsman to help lead applicants through the complicated developments process.

Commenting on the new proposals, which would cover residential construction, Robert Cf. Johnson, executive vice president of the Northern Virginia Builders Association, said, "Anything in the way of a reduction in the time period is meaningful."

But, Johnson said, builders are concerned about another development that could stretch out, rather than shorten, the approval process.

The issue, to be considered next week by the supervisors, is whether the Planning Commission should review site plans after a rezoning application is accepted. If the commission gets this additional power of review, Johnson said, 60 to 90 days would be added to the pre-construction process.

The lenghty approval and review process did not come about because of bureaucratic power seeking or inertia, though builders cometimes seem to think so. Many of the steps builders are now required to fulfill were added in reaction to the pell-mell development that often occurred in the early days of suburbia.

The Planning and Land Use System, Fairfax's highly publicized PLUS program, which was adopted in 1975, sets environmental standards which require inspections and approvals, lengthening the development process.

But though the entire process seemed to hve a theoretical rationale, criticisms, even from within the county government, have been mounting.

John F. Herrity, chairman of the Board of Supervisors, has been critical of the department of environmental management, the county office that oversees the actual construction process. Top county officials are now searching nationwide for someone who can take over as director - the position has been filled temporarily since spring - and revamp operations, which criticsay are tied up in bureaucratic knots.(TABLE) (COLUMN)*2*Average Time (COLUMN)*2*(Weeks) Process(COLUMN)1976(COLUMN)1977 rezoning(COLUMN)52(COLUMN)39 Search Plan Review(COLUMN)2(COLUMN)2 Preliminary Plan Approval(COLUMN)11(COLUMN)8 Subdivision Plan Approval(COLUMN)49(COLUMN)40 Construction and Grading Plan Approval(COLUMN)1(COLUMN)1 Construction (From Issuance of Building Permit)(COLUMN)84(COLUMN)72 Total(COLUMN)199(COLUMN)162(END TABLE).

Northern Virginia Builders Association maintains thatthe average house can be constructed in 75 days or less