Officials said the materials were stored improperly and located on the second floor of the building.
Crews began razing the building Tuesday.
The fire was reported Monday afternoon, and was under control within an hour. Fire officials said the flames pushed through the building with help from heavy winds.
Fire officials said it could have been much worse because all the buildings in the area are sided with cedar shingles.
No injuries were reported.
The beach is still scheduled to open for the season Saturday.