For three days, architect Norman Richard Kraus has been directing construction of a 400-ton replica of England's Windsor Castle, and it doesn't bother him in the least that in a matter of days it will all be gone.

"All things are in a period of deterioration," Kraus said yesterday as he surveyed his latest creation. "It just matters if you count time in years or minutes."

This is the third year Kraus and friends, members of Sand Castle Ltd. have gathered over Labor Day weekend to create a mammoth sand castle, and Windsor Castle, along with its adjacent village of Eton, is their most ambitious project yet.

With a scale of one foot for every 100 feet, the castle has been carved from a mound of sand stretching 30 feet high and almost 150 feet long.

Kraus and his wife, Marla, began planning the project in May. The core group of builders began camping on the beach at dawn Friday. They worked steadily through the weekend, with help from anyone who happened by, and were planning to add the final touches late last night.

Thousands of people descended on the Del Mar beach to watch and help. They rode horses or surfboards, paddled canoes or walked to the setting a few dozen yards off the Pacific Ocean along the San Dieguito River. Which played the role of the River Thames.

Newcomers were put to workshoveling sand or keeping completed sections damp. Experienced workers created towers and turrets, balancing on top of the fragile mountain of sand.

"This is an art form whose time has come," said Todd Vander Pluym, a Los Angeles architect and sculptor Michaelangelo's David in sand.

"It is a satisfying pasttime," he added. "It is inexpensive and you don't have to clean up after yourself."

This year the California Coastal Commission had to issue a permit for sand to be bulldozed up from San Dieguito Lagoon. The Big Yellow Machine Co. donated the heavy equipment. All was going well until the residents of the exclusive Sandy Lane development hired an attorney to fight the castle permit.

The residents claimed last year's erection of Mont St. Michel on the nearby beach attracted trespassers, litter and rowdies. Sandy Laners argued their position before the Del Mar City Council - unsuccessfully.

A permit was issued to Kraus by a unanimous vote, and Mayor Herv Sweetwood was here all day with a shovel.

"The problem I faced as mayor was how to resolve a conflict of interests," said Sweetwood. "It is sort of a shame the residents are upset over such a neat event."

Kraus and Vander Pluym have been building castles for about 10 years.Windsor Castle was especially challenging because the hot weather dried out the sand and there was an extraordinary amount of rocks to be sorted out. Being purists, they work only with sand and sea water.

Sand-castle builders came from all over the state. In addition to the architects and contractors who directed operations there was a corporate planner for San Diego Gas and Electric Co., a ballet dancer, several teachers, librarians and engineers. Their copy of Windsor included details as small as windows and shutters, and toward the end, the builders were adding horses and people.

The sky above Windsor Castle in Del Mar was a brilliant blue. The tide came in on cue and Kraus, bronzer than all the rest, puffed contentedly on a small cigar.

"It is the doing it that counts not weather it lasts," he said.

The city permit raquires Windsor Castle to be "reintegrated" into the beach by this Friday.

When Sweetwood was asked how this would be done, he smiled and said, "By small and large feet trampling in some sort of ritualistic dance."