Protecting Decks, Patios, and Porches

Risk Factors:

Shown is a California Chapter 7A compliant decking product (left) and a non-compliant product (right). Both are wood-plastic composite decking products.

 Are the materials used to construct the deck, patio or porch combustible?

  • Examples of combustible materials include solid wood or wood plastic composite products.

  • Some manufacturers are now incorporating fire retardant chemicals into their products, and fire performance information for many decking products is now available on the manufacturer’s website.

  • Wood decking treated with an exterior fire retardant also is available.

Do you have combustible materials stored under or on top of the area?

Is nearby vegetation well maintained?

  • Combustible materials and vegetation can act as a wick and allow the fire to move to the deck and other building materials, igniting it and other items stored underneath or nearby.

  • This is particularly important for decks when the house or business is sited on a sloped lot.

  • Depending on the type and condition of the vegetation, flame lengths on a slope can reach more than 30 feet, so even an elevated deck can be vulnerable.

Steps to reduce the risk of wildfire damage:

Enclosing an elevated deck, patio or porch: 

  • To determine if enclosing your deck, patio or porch would be beneficial, consider whether you store combustible materials underneath it, or if your vegetation management plan is inadequate, particularly in the 0- to 30-foot zone.

  • Avoid storing flammable materials on top of or beneath the deck.

  • Providing sufficient ventilation or other means for water to drain out is a critical step in the enclosure process.

    • The national building code standard requirement for a crawlspace is one square foot of venting for each 150 square feet of floor area. Allow at least this much ventilation and maybe more if you are in a particularly wet area. If you do not allow any wood or wood-based structural support members and boards to dry out, fungal decay will become the biggest threat to your deck, patio or porch.

  • Enclosing your deck, patio or porch will not reduce the risk of the top being exposed to embers. For that, the best protection is to keep the surface clear of leaves, pine needles and other vegetative debris.

  • If the house is supported by a column and beam system, and it doesn’t have skirting around the perimeter, add a skirting of a noncombustible material.

  • Remember to provide vents on all sides to ensure proper ventilation. California’s Building Code has taken the lead in developing guidance for wildfire protections. Learn more about how to choose wildfire-resistant decking materials.

Installing flashing:

  • Attaching a metal flashing strip, approximately 18 inches tall, between the top of the deck, patio or porch and the exterior (combustible) siding can create a barrier between exposure to burning debris ignited by embers and flames near the point where the house intersects with the deck, patio or porch.

  • When attaching the flashing, make sure it is tucked in behind the siding where the top of flashing terminates. This will help prevent water from seeping between the flashing and the siding.

  • Alternatively, if you can find a noncombustible siding material with a similar pattern, the lower two or three courses of siding could be replaced.

Replacing a deck, patio or porch: