Some apartment units at a North Seattle retirement complex must be partially dismantled to check for falsely labeled lumber from a British Columbia wholesaler, a city building official has decided.

A structural engineer's study will determine how much wallboard will have to be removed from completed apartments at the Ida Culver House at Broadview, a 250-unit retirement complex at Greenwood Avenue North and North 125th Street, said Will Hairston, the city's acting director of construction inspection.

Inspectors already have informed the builder, Koll Construction Co., that some wallboard must be removed, he said. ``We just don't know how much.''

Hairston said he didn't know when the inspections would begin. The engineer's report should be complete within several days, he said.

It's unclear whether any of the approximately 100 residents in three completed Ida Culver buildings will be forced to move out during the inspections, he said. If lumber with phony labels is found inside walls, it probably will be reinforced with certified lumber, he said.

Falsely labeled 2-by-4 studs were found in one unfinished apartment building and two single-family units at the complex Friday. The studs are lower-grade wood mismarked as fit for structural use.

Residents of the two completed structures are in no danger, Hairston emphasized.

``We don't feel there's any danger to the structure,'' he said. Walls in the buildings have been built beyond specifications, he added.

But inspectors must examine studs inside walls in the completed buildings, Hairston said. ``We're trying to confirm exactly where it's located.''

Koll Construction officials declined comment yesterday. A Koll construction manager last week said he was confident none of the mislabeled lumber had been used in the three completed structures, which opened Nov. 1.

The Ida Culver complex last week became the city's first building project found to contain lumber marked with a phony lumber-grade stamp from MacDonald Inspection Services of Coquitlam, B.C.

The bogus grade marks have misidentified softer, weaker wood - such as spruce - as stronger species typically used as structural supports. In other cases, knotty wood deserving a low No. 3 grade has been mismarked as grade No. 2, which is suitable for structural use.

The wood was shipped directly to dozens of greater Seattle-area construction sites in recent months by B.B.M. Lakeview Wholesale Lumber of Surrey, B.C. At some point, the original grade stamps had been sanded off the lumber and replaced with labels indicating structure-rated wood, officials say.

B.B.M. Lakeview pleaded guilty in 1988 to delivering fraudulently graded lumber to B.C. customers.

Canadian authorities are trying to determine who altered grade marks on several million board feet of lumber shipped to this area by B.B.M. in recent months. No arrests have been made.

Suspect boards were uncovered at large-scale construction sites from Everett to Federal Way last week as word of the phony labels spread among building inspectors. The Ida Culver House and an apartment complex in Monroe were the only sites where occupied buildings were suspected of containing falsely labeled boards.

Lumber wholesaler's records have traced shipments to about 35 local construction sites, said Greg Clarke of MacDonald Inspection, which authorizes numerous B.C. mills to use its grade stamps. But officials say it's unclear how long the mislabeled boards have been in the Puget Sound construction market, or whether they were used in any other structures now occupied.

A stop-work order, meanwhile, remained in effect today on a second Seattle construction project, Bitter Lake Apartments on Linden Avenue North, where suspect lumber was discovered Friday.

Building officials in other cities around Puget Sound said projects were in varying states of delay as lumber experts and structural engineers studied buildings believed to contain lower-grade lumber.

MacDonald Inspection and the American Lumber Standards Committee, which monitors compliance to international lumber-grade rules, are conducting their own investigations, spokesmen said.

Officials with Broadview Development Associates II, which owns Ida Culver House, could not be reached for comment.