When the National Association of Home Builders and its members build homes, they generally do things by the book: with building permits, skilled construction crews, and quality lumber.

But yesterday, even as workmen put the finishing touches on a model "house" in front of NAHB's headquarters at 15th and M streets NW, District officials complained that the association had failed to obtain the required permit to build the one-story structure.

"There is no permit for that building and no special arrangement made to get a variance from the building code," said Joyce McCray, spokeswoman for the Consumer and Regulatory Affairs Department, which issues a variety of permits for new construction in the District.

NAHB officials said that the house, built for the organization's convention next week, was designed to dramatize the "unnecessary" government regulations that add thousands to the cost of actual homes.

The building, called a "visible house" because passersby can view its rafters and wall studs, was constructed using modern building techniques that often are barred under local building codes, the NAHB said. One of the methods involves using half the wood of a conventional house without reducing the home's structural strength.

"Licenses and Permits told me we didn't need a permit," said David D. Dalo, NAHB's director for standards and codes. The District official, whom Dalo could not identify, waived the building permit because the house would be torn down this summer and is set back several yards from nearby sidewalks, Dalo said.

"Building codes are meant for habitable structures, and this isn't one," Dalo added.

But District officials disputed that view, contending that there are virtually no exceptions to the law requiring legal permits to be posted at construction sites. Permits are not required for structures that have less than 40 square feet of floor area. The NAHB's house, with 12-foot sides, has more than three times this floor area.

"Temporary or not, every structure under construction has to have a permit," declared Ahmet Ozusta, the city's chief structural engineer.

McCray said that her department will send an inspector to the site on Monday.