Three kayakers with the Ikkatsu Project wrote in a report this week that they found the remnants June 12 as they worked their way up a beach near the northwestern tip of the Olympic Peninsula, about 120 miles west of Seattle on the Makah Indian Reservation.
They discovered a lumber pile mixed in with driftwood and seaweed. The lumber's dimensions were metric, and some of it was stamped with a serial number they traced to a mill in Osaka - the Diawa Pallet Housou Co., the kayakers wrote.
Some of pieces were nailed together, kayaker Ken Campbell said Tuesday.
In the same area, they found other household items, including a glass bottle of cherry-flavored cough syrup and a red container of kerosene with Japanese writing. Kerosene is widely used to heat homes in Japan.
It was exciting to find what appeared to be the remnants of a home, Campbell said.
But he added: "It was sobering, especially when you're smelling somebody else's cough syrup. Somebody lived here and it doesn't look like a house anymore. I was not prepared to find something like that."
Curtis Ebbesmeyer, a Seattle oceanographer who is on the expedition's advisory board, said it is too soon to confirm whether the debris was from a Japanese home.
"It's like an archaeological dig," he said Tuesday. "It's a bunch of things that could be construed as a house."
If so, it might be the first case of a Japanese home floating 5,000 miles across the Pacific Ocean following the devastating earthquake and tsunami of March 11, 2011.
A 66-foot dock ripped loose by the big waves landed on an Oregon beach this month, and officials confirmed Tuesday that a 20-foot boat that washed ashore at Cape Disappointment State Park in southwest Washington last week came from Japan.
The arrival of debris from the tsunami has worried officials on the West Coast and in Alaska. They say it will be expensive to clean and could carry invasive species - a serious threat to the fishing industry. On Monday, Gov. Chris Gregoire called for federal help dealing with the debris.
The kayakers - Campbell, Steve Weileman and Jason Goldstein - are longtime friends who had wanted to kayak the Olympic Peninsula's Pacific coast and decided to survey the beaches along the way.
They aren't scientists, but they contacted Ebbesmeyer and others to learn surveying methods that would be useful to researchers, Campbell said.
They named their expedition the Ikkatsu Project after a Japanese word for "unity," and they are dividing the trip into three segments, the last of which will be completed in August.
The team's work will help establish a baseline for measuring how much more tsunami debris arrives this fall and winter, Ebbesmeyer said.
The kayakers said they didn't have the resources to search through the entire lumber and debris pile, and Campbell said they didn't find anything with a name or address - though in retrospect, they could have looked harder.
"It was my first time finding a house, what can I say," Campbell said. "Next time, I'll be much more thorough."