Firewise's new wildfire research fact sheet has some great information on how to reduce the ignitability of your deck or lanai. It's just one page but packed with useful information.
From the Source:
"MANY HOMES LOCATED IN WILDFIRE-PRONE AREAS HAVE ATTACHED DECKS, WHICH CAN POTENTIALLY SPREAD FIRE TO THE HOUSE WHEN IGNITED DURING A WILDFIRE. A burning deck can ignite siding or break the glass in doors or windows, allowing fi re to gain entry into the house. Consequently, making decks less vulnerable to wildfire also makes your house less vulnerable. Reducing the deck’s vulnerability requires an approach that focuses on the materials and design features used to build the deck, and creating a noncombustible zone around and under the deck."