Fences (and walls) are both decorative and functional (for security and privacy) and come in many materials and configurations. While we have no laboratory fire test data on fences,there are a number of observations that indicate fences — like vegetation — are a much greater hazard close to a house. Fences and gates can also be an access problem for fire crews trying to enter your yard, so it is advisable to get an inspection from your local fire department.
The fence shown below was responsible for substantial damage to both adjacent houses that were saved only through intervention by firefighters.
The house on the right had a gate attached to the front corner of the garage. The gate was totally consumed as were most of two 8-foot sections of fence. The geometry and combustibility of this arrangement was an invitation to burn in this type of "zero-lot-line" construction. There are several reasons for fences to be of concern. For one, a combustible fence or gate attached to a structure is an obvious threat if it catches on fire. The fire can arise in a number of ways. One is that debris (leaves, trash, etc) often collect at the bottom.
Another problem is that wooden fence boards in contact with soil will eventually decay in that area.
Combined with combustible debris, fences can be an excellent fuel source. Also, fence boards usually have small vertical openings where brands can lodge and even cause the fence boards to ignite directly. In all cases, the thinner the fence boards, the greater the risk!
Any fences or gates that are attached to houses should be designed to reduce the fire hazard. Metal gates and heavy wooden fence sections can minimize this problem. Below is a combination of wooden framing with wire mesh, which minimizes the amount of combustible material in the fence.
For fences in "zero-lot-line" situations, consider using a noncombustible material, ignition-resistant lumber (fire retardant treated for exterior exposure), or thicker dimension lumber (1 1/2 inch). Another option is to use a chain-link fence with climbing vines to provide privacy. The vines must be maintained so that they do not become a fire hazard.
Keep the bottom of fence boards clear of debris (leaves, trash, etc) and make sure that they are not in or touching soil. A good rule of thumb is to create about a one-inch gap at the bottom.
Do not store combustible materials (such as firewood) against fences.