What Is the Difference Between Wet Rot and Dry Rot?

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Dry rot (Photo: @dezign747 via Twenty20)
Both wet and dry wood rot are common problems that many homeowners face; however, they can be sneaky and grow a considerable amount in a short period of time. When left unattended, they can cause significant damage to building’s structure, which is why it is crucial that you know how to identify and treat the different types of rot.

What Causes Wet and Dry Rot

Wet Rot: This is the most common type of wood rot. It can appear when any unprotected timber is exposed to damp conditions of around 50% moisture. Wet rot requires a constant source of moisture, and the damage will be limited by the range of such moisture. When left unattended, this rot can cause severe damage.
Dry Rot: Dry rot appears when the timber is exposed to conditions of at least 20% moisture, which is relatively easy to achieve. This type of rot is usually present when things such as leaking roofs, defective gutters, and plumbing leaks happen since it allows for dampness penetration.

How to Identify Wet Rot and Dry Rot

Wet Rot:
  • Timber shrinks, causing cracking
  • Timber feels soft and spongy to the touch
  • Discoloration is not unusual
  • Stays on the damp area and does not spread
  • Paint finish can appear damaged
  • Presence of a musty smell
  • Possible presences of black fungus
  • Appearance of fungus will be limited to the areas affected by dampness
Dry Rot:
  • Timber shrinks and cracks
  • The rot may leave a surface veneer that can hide the rot
  • Timber can feel soft and spongy to the touch
  • When exposed to light, the fungus can have a yellowish tinge to it
  • The fungus might have turned gray
  • Damp musty smell
  • Presence of mushroom-like bodies depending on how old is the rot
  • Red spore dust from said bodies may be present
  • Paint finish can appear damaged
  • Dry rot can grow along walls of a property to find more timber to attack

How to Treat Wet Rot and Dry Rot

Both types of rot should be treated as soon as possible and by professionals. The lack of timely and proper measures can result in great damage to the structure of the building.
Wet Rot:
  • Identify the source of the moisture
  • Repair the source of dampness (such as defective internal plumbing)
  • Strip out the affected area
  • Repair or replace weakened timber while protecting the new one from dampness
  • Apply a fungicidal treatment to near-by timber that may be at risk
  • Ensure the rot attack has been successfully neutralized before reinstalling walls, floors, or ceilings finishes
Dry Rot
  • Identify the source of moisture that is causing the dry rot
  • Repair the source of dampness (such as defective internal plumbing)
  • Strip out affected areas
  • Repair affected structural timber and protect them from any further dampness
  • Treat the area with antifungal treatment; this will provide the affected area with a chemical protective barrier while it dries
  • Ensure the rot attack has been successfully neutralized before reinstalling walls, floors, or ceilings finishes
While these steps may seem simple, and you may be tempted to do it yourself, we always recommended calling a professional for help. Because of the various overlapping characteristics, many people have trouble identifying which type of wood rot is affecting their home. And, without a proper diagnostic, you won’t be able to achieve a proper treatment. Instead of running this risk, it’s often advisable to let a professional deal with the rot.