Mary Whittington says she found just the house she wanted in a new Charles County subdivision. She signed a contract and put down a $1,000 deposit last March, later paying about $2,000 more for extras such as carpets and additional electrical fixtures.

A buyer was waiting to close a deal on her present home in Oxon Hill, and Whittington planned to put $50,000 from the proceeds into the new home. She was told in July that an FHA-insured loan had been approved for the remainder of the $71,450 sale price, she said.

But in the meantime, David Whittington, her son, had taken a closer look at the house and found what he believed were serious problems.

"I kept seeing things wrong with the house ," said David Whittington. "My mother is 66 and she has cataracts. This is a disgraceful way to treat her."

Today, after hiring two lawyers and spending several months wrangling, Mrs. Whittington has her money back and is out only her time, effort and lawyers' and engineer's fees. The house is still owned by the builder, Mil-Mar and Sons Builders, Inc., of LaPlata.

Mrs. Whittington, who did not go through with the sale of her Oxon Hill house and is still living there, said she is so unnerved by her experience that she cannot even think of looking for another house to buy now.

No official of Mil-Mar and Sons could be reached for comment, but a woman at the firm's office said that the company's work always meets all codes and "we've never had any complaints on any of our houses."

An attorney for Mil-Mar and Sons, George Andrews, said the firm has "one of the best reputations in the county and in the construction field." Andrews added that if county inspectors find the house "defective, obviously it will be brought to standards" and any "deficiencies will be corrected."

The Whittingtons' story shows how a prospective buyer can be approved for an FHA-insured loan and the house can be covered by a 10-year warranty from a construction-industry-owned corporation without inspectors for either organization seeing the house.

County inspectors say the house failed to pass two county housing inspections of its framing last April and had not been issued a use and occupancy permit, which they say is required before a sale can be completed.

Although Charles County regulations require that a house be inspected, the builder has not notified the county since April that the home was ready for other inspections at various stages of construction, said Carl Riffle, chief housing inspector.

Mary Whittington, a widow, wanted to move to the St. Charles development to be nearer her son, other children and grandchildren. She picked the small, two-bedroom house from plans. She said the layout appealed to her as something she could manage at her age.

It was only as the house neared completion that problems began to emerge, she said. She said she sought to convince the builder to correct the problems her son spotted or return her money.

The mother and son consulted John Cassidy, an Upper Marlboro attorney, who recommended they ask an engineering consulting firm to inspect the house.

The resulting report from engineer Victor G. Hare of Bowie, dated July 29, cited "several serious structural defects," including:

* "The concrete piers holding up the center wooden girder are . . . structurally unsound . . . . The piers are set in shallow recesses, full of water and mud, instead of on . . . concrete footings. The piers are sinking and the middle pier is leaning over at a dramatic angle. The concrete blocks were stacked incorrectly with some in a flat, weak orientation and all without cement mortar in the joints. The east pier has the top concrete block cracked completely through."

* "The center triple 2-inch-by-10-inch wooden girder holding up the first floor has sagging sections . . . "

* Construction methods used "will cause the carport roof ridge to deflect downward and the horizontal thrust to bow the front and rear beams outward." The carport also needs "additional roof rafters . . . steel tie rods . . . from the front to the rear beam to hold the sides in place. The carport corners should have larger support columns for the header beams."

"There are numerous other defects indicating poor quality control," the report continues, including problems with the wooden deck in the rear of the house, with the roof, rear patio door, sewer drain pipes, attic ventilation, and the front door threshold. The report also cited broken plaster around the laundry area, chips in bathroom mirrors and noted that "most of the bi-fold closet doors are missing knobs."

Hare is a civil engineer, licensed to practice in Maryland, Virginia and the District of Columbia, he said. His firm, Adelberg, Hare and Associates, specializes in residential and commercial inspections.

County housing inspector Marion Richards, who looked over the house this week after receiving a query about it from a reporter, said he also found "structural problems under the house." A foundation pier is "made out of hollow block, instead of solid block, as the building code requires. One pier, the center pier, . . . is leaning to one side. It's possible there is not any concrete footing under the pier because of the way it is leaning," he said.

Richards said he did not go underneath the house, "because the access panel is too small."

Richards, who said he found other defects also reported by Hare, said that because the house has been completed without passing any inspections during construction, the county would require "an engineer's certification on the house" before issuing a use and occupancy permit. Chief Inspector Riffle said the house cannot be sold unless it receives this permit.

Mil-Mar and Sons attorney Andrews said, "I strongly feel this particular transaction and these problems are being taken out of context."

Attorney Cassidy said that in July "the direction of the Whittington case was going toward litigation." Cassidy said he is "not a litigation lawyer," and at that point referred Mrs. Whittington to another attorney, Peter W. Collery of Prince Frederick.

"Two options" were open to her, said Collery. "If they the builder insisted on us going to settlement, we could go to court. Or we could attempt to negotiate a settlement and let everybody go back to square one."

Collery said he and Andrews, the builder's attorney, were able to agree on a settlement.

In mid-October, the builder gave Mrs. Whittington her money back.

Spokesmen for the FHA and the Veterans Administration said neither agency requires inspection of homes covered by Home Owners Warranty Corp. (HOW). Only an appraiser is sent to determine the value of the property. In these cases, homes can be covered by FHA or VA insured loans, but the purchasers cannot qualify for government assistance in correction of structural defects, they said.

A spokeswoman for HOW said the firm normally "checks and certifies" construction firms before they are given HOW coverage but HOW does not inspect each home that it covers. The St. Charles builder "has 57 homes in the HOW program, and we have never had a complaint or claim" involving these houses, said the spokeswoman, Jane Snow.

She said, however, that a HOW inspector who checked the Whittington house late this week did find serious defects. But she noted that the inspector looked at several other Mil-Mar and Sons houses, "all of which are fine."

She said "there is some responsibility on the part of the consumers" to notify HOW that problems may exist in houses they want to purchase. HOW has been in existence less than three years, however, and many buyers may not be sophisticated enough to seek out the corporation's aid before completing a sale.