Ahrens and other officials have met with architects and contractors to review the changes, which range from requirements for stronger bracing for wood-frame construction to the rise and tread of stairs.

"It's kind of a big deal," said Ahrens, who said changes in the state's code are the biggest since 1998. "It's substantially different than what we are used to."

Mill Valley architect Brock Wagstaff, a 30-year veteran of building in Marin, said the industry is accustomed to changes. Besides changes in state law, each local city has its own rules, he noted.

Ahrens said that among the biggest changes are stricter requirements for fire sprinklers, tougher seismic-safety standards, increasing the rise and run on new stairs and making railings 42 inches high - 6 inches higher than the current standard.

Steps on new stairs in private dwellings will have to be a little shorter and deeper. And the code now requires that the tread is at least 10 inches deep, an inch more than in 2007.