Dry rot is a weakening of wood caused by one of several species of fungus. The fungus digests the parts of the wood that give the wood strength and stiffness. Weakened wood is typically somewhat dry, hence the name dry rot, and brittle.
Ironically, dry rot usually results from too much moisture in contact with wood. The dry rot fungus has the unusual ability to transport water from wet areas to dry areas allowing the fungus to grow even in relatively dry wood. If not stopped, the dry rot fungus will weaken wood so that it may eventually disintegrate.
The picture to the right shows the dry rot that we found during the residing of the customer's house. If the dry or excess moisture is not eliminated, it can attract termites. This is highlighted with circles in the picture below.
Preventing dry rot damage
The most important way to prevent dry rot damage is to reduce or eliminate excess moisture. This may be as simple as repairing old caulking on siding or as complicated as removing the old failing siding and sheeting. A common cause of dry rot and termite damage is inproper flashing while siding. FLASHING is the most important step in siding a house and is the one area that most people overlook.
Signs that you might have dry rot
Dry rot first appears as off-white in color
You may see mushroom like spores
Deep cracks running across the grain of wood
Badly effected wood is soft or crumbles to the touch!
The most common area for dry rot under an improperly installed window!
Treating dry rot is a three step process:
Step 1 is to locate and stop the source of the moisture which caused the problem in the first place. Until the source of the moisture is found nothing productive can be done.
Step 2 is to replace any wood that is so damaged that it has become structurally weakened.
Step 3 is to treat new and existing wood with borate to prevent growth of the dry rot fungus and kill any fungus in the treated wood.
Dry rot - due to improper flashing or no flashing
This dry rot was found on a house that was only 10 years old.
Dry rot around a chimney that was improperly flashed (see our page on flashing)
If you think you have dry rot attacking the siding or window trim of your house,
it's probably best to have the problem looked at.
"The longer rot is left untreated, the further the decay can extend,
causing additional disruption and increased costs when the problem is addressed."