Rot is a common fungal disease that affects fences made from wood. Different species of fungus grow in specific circumstances and create their own telltale forms of rot. Knowledge of rot basics can help you diagnose the cause of many types of damage in your fencing materials. Knowledge also plays an integral part in prevention. In fact, a few simple steps can help you avoid developing rot-related problems in the first place.

Wet Rot

Wet rot is the name for rot caused by excessive exposure to moisture. As a rule, it occurs when wood’s moisture content reaches at least 50 percent. The most common source of wet rot is a fungal species known as C. puteana, or cellar fungus. However, a variety of other fungi can also produce the same problem.

In a fence, wet rot tends to appear near the ground. That’s because the earth can hold large amounts of moisture for extended periods of time. In addition to the main fencing material, rot can occur in any wooden support posts.

Signs of Wet Rot

A range of issues can point to the presence of wet rot in your wooden fencing materials. Things to look for include:

  • A musty, damp smell in the area near your fence
  • Wood that feels spongy or soft to the touch
  • Areas of wood that look darker than the surrounding material
  • Obvious signs of fungus growth on the surface of your fence
  • A flaky or damaged surface on a painted fence
  • Soft wood beneath the intact surface of a painted fence
  • The presence of warped fence slats or posts

When a fence damaged by wet rot dries out, it will tend to crumble or crack under very little pressure. Areas affected by this form of rot sometimes look lighter than the surrounding wood, not darker.

Dry Rot

Dry rot is caused by species of fungus that thrives at lower moisture levels. Despite its name, the typical moisture content for affected wood is about 20 percent. You may also see this form of fence damage referred to as brown rot. The fungal species responsible for dry/brown rot spread by pulling moisture from wetter areas and transferring it to drier areas.

Signs of Dry Rot

Some people mistake signs of dry rot for signs of damage caused by termites or carpenter ants. However, rot-affected wood is typically drier than insect-affected wood. Also, it will lack any indications of insect passageways or living insects. Specific symptoms of dry rot include:

  • Wood with deep cracks in its grain pattern
  • A damp, musty smell
  • Wood with an abnormal brown color
  • Wood that crumbles upon touch
  • The presence of grey strands that resemble spider webs
  • White, wooly patches known as mycelium
  • The presence of fungal “fruiting bodies” that look like mushrooms

White Rot

Certain fungal species can create another type of fence rot known as white rot. These species produce enzymes capable of breaking down the cell walls of wood. As a result, they can trigger severe forms of damage. White rot tends to occur in fences made from hardwood.

Signs of White Rot

A fence affected by white rot can turn from solid wood into a stringy, sticky material. Other indicators of this form of rot include:

  • Spongy wood
  • Soft wood
  • Moist wood
  • An abnormal white color
  • An abnormal yellow color

Preventing Fence Rot

You can take several steps to prevent rot in your wooden fence. Effective techniques include:

  • Using rot-resistant wood – Some species of wood are more resistant to rot than other fencing options. Good options include hardwoods such as redwood, cedar, oak, and cypress.
  • Using pressure-treated wood – Pressure treating is a process that forces preservative chemicals into wood’s interior. These chemicals help deter rot, as well as insect infestation.
  • Using stain – In its raw state, wood has a natural tendency to absorb moisture. You can curb this tendency (and decrease your rot risks) by applying a protective coat of stain at installation. Follow up with a reapplication every one to three years.
  • Following installation best practices – Rot is less likely to affect fences that have correctly installed posts. One of the critical steps in proper setup is keeping the posts clear of direct soil contact.
  • Maintaining a clean fence – Regular cleaning will help keep your fence rot-free throughout the year. Experts recommend a bleach-and-water solution applied with a hose or a pressure washer set on low.

If rot appears on your wooden fence, you can prevent its spread by replacing any affected slats or posts ASAP.