Causes of Spongy Wood

Dry Rot

• Dry rot causes the wood to have a crumbly, rough and cracked appearance. The wood is powdery and may begin to disintegrate when touched. Several fungi cause dry-rot decay and erode the structural qualities of lumber. High humidity and moisture-laden environments propagate the fungi. They will eventually break down the wood, leaving it spongy and soft.

Insect Damage

• Termites and "woodworms" commonly infest wood and leave a spongy texture after heavy infestations. The woodworm is actually the grub stage of several beetles such as the weevil, powder post and furniture beetle; the grubs feed on the wood. Termites are familiar wood-boring insects that also feed on wood, causing extensive structural damage as they eat and drill tunnels. The termite leaves dusty "frass" (droppings) and telltale crevices. Both termites and woodworms weaken the lumber, leaving it soft and spongy. These infestations encourage mold and fungal infection, which further undermine the integrity of the wood.

Exposure and Mold

• Wood exposed to the elements is prone to early sponginess. Harsh weather conditions and dampness invite insect, fungal, bacterial and mold infestations. Look for black, white or greenish mold and fungi, including mushrooms.

Age

• The age of the wood can contribute to spongy breakdown. Old wood that has been exposed to decades of temperature fluctuation and varying degrees of humidity softens and begins to break down into a spongy texture. Dampness can also encourage mold to begin attacking the older wood, leaving it soft and spongy. Wood in damp areas of the house, such as basements and bathrooms, is particularly prone to sponginess due to the damp environment.