Let start with the two types of dry rot that can damage wood.

Brown rot, which can be caused by three different strains of fungus and usually affects softwoods, such as doug-fir, which is used as framing in most southern California homes. Brown rot is the more serious of the two types of wood rot. It causes the wood to develop a mottled checkerboard appearance and then turn into powder, and can grow through damp drywall, plaster and mortar to attack the wood.

White rot affects hardwoods and softwoods alike and causes the wood to break down longitudinally along the grain into coarse fibers. Unlike brown rot, which can develop in conditions of high humidity, white rot only grows when the wood is actually wet.

For southern CA the worst is like a monster movie. This fungi is called Meruliporia Incrassata (“Poria”) and it eats wood like a cancer.

“Poria” is a brown rot fungus, and as such the decayed wood will look just like the decayed wood from any other brown rot fungus (the ones that rely on leaks for their required moisture such as window or roof leaks).
There are distinctive characteristics that can be used to identify “Poria” in the field. The first of these is the water conducting rhizomorph which transport water by capillary action from a constant source (usually damp or wet soil) The second is the spore producing ‘fruiting body.

“It’s a rare fungus, but it’s as common here as anywhere in the world,” said UC Riverside plant pathology professor John Menge. “It’s also the most devastating wood-decaying fungus of houses that we know of”
What Can You Do About Poria Once it Infects Your Building?
Unfortunately, “Poria” is located in soil and once it is allowed to make the transition from the soil to the building’s wood members, the only remedy is cut out the effected wood, install new wood and then create a barrier so the “Poria” cannot re-infect the wood in the future.


What Can You Do to Keep Poria From Infecting Your Building?

Fortunately, “Poria”’ is also very sensitive to dehydration (drying out), so the key is to avoid construction details that allow the rhizomorph to reach the structure. Compliance with the building codes with respect to proper clearances between wood and soil conditions are extremely important in preventing infestation by “Poria”. Most of these construction issues listed below are the result of the failure to follow the building code which allows “Poria” to infect buildings by allowing the following conditions to exist:

Soil allowed to come in contact with wood

Stucco installed below soil grade

Siding allowed to extend below soil grade

Inadequately vented crawlspace (not properly vented, inadequate earth-wood clearance)

Cracks in perimeter foundation and slab on grade allowing migration of rhizomorphs to reach wood

Planters placed against exterior wall with soil contaminated with” Poria”

Sprinklers or other water source creating ‘ponding’ near the home (related to poor grading)

Failure to slope the soil away from the building causing excessive moisture and avenues for Poria infestation

Failure to maintain proper clearance between landscaping and wood members of the structure

Poria Incrassata is more sensitive to higher temperatures than most decaying fungi and is killed in moist wood at temperatures only moderately above “air-temperature maxima”. This explains why poria occurs in the more protected parts of structure and not in wood exposed to full sun. In other words, poria is extremely sensitive to drying. In naturally infected wood, it can only survive for 32 days of air drying. In laboratory tests, all artificial infections were dead in 1 day at 10% RH (relative humidity), 5 days at 65%, and 10 days at 90%. Sensitivity to drying, in conjunction with the need for conducted-water, forms the basis for the presently recommended simplified control and remediation measures

All of these conditions allow “Poria” to enter the structure without experiencing a drying environment. Therefore the key to avoiding “Poria” damage is to avoid (or repair) the construction details that allowed entry in the first place. Although this appears to be a simple solution in principle, it can be expensive and require extraordinary retrofitting of the site conditions to implement for an existing structure.

If you have any questions regarding wood rot and or would like to schedule your free estimate Call Best Rate today at 619-229-0116.

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