Fungus on Wood: What It Is and Why It Matters

Fungus on wood develops when moisture is present for extended periods of time. Wood naturally contains organic material that fungi feed on, but without moisture, fungal growth cannot survive. When leaks, condensation, poor ventilation, or ground contact introduce excess moisture, fungus can begin to grow and spread within wood structures.

How Fungus Damages Wood

Wood-decay fungi break down the fibers that give wood its strength. Over time, this causes the wood to:

• Become soft, brittle, or spongy

• Lose structural integrity

• Crack, crumble, or break apart easily

This type of damage is often referred to as wood rot, and it can seriously weaken framing, beams, subfloors, and other structural components if left untreated.

Common Causes of Wood Fungus

Fungal growth on wood is commonly caused by:

• Plumbing leaks or roof leaks

• Poor drainage around foundations

• High humidity and inadequate ventilation

• Wood-to-soil contact

• Past water intrusion that was never fully dried

Even after a leak is repaired, fungus can continue to grow if the wood remains damp.

Signs of Fungus on Wood

Warning signs may include:

• Discoloration or dark staining on wood

• A musty or earthy odor

• Soft or crumbling wood when touched

• Visible fungal growth or web-like patterns

These signs often indicate long-term moisture issues that should be addressed promptly.

Why Treatment Is Important

Treating fungus on wood involves more than surface cleaning. The moisture source must be corrected, and affected wood may need fungicidal treatment, drying, reinforcement, or replacement depending on the severity. Addressing fungal decay early helps preserve structural safety and prevents further deterioration.

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