Here’s are our “Three Rules of Rot”:
- 1) Existing wood rot fungus colonies are constantly sending our spores into the air. These spores are floating around pretty much everywhere in the wind. It’s not necessary to have an area of wood rot nearby for spores to land on an exposed surface of wood. There are likely already plenty of wood rot spores on the surface of any wood exposed to outdoor, unfiltered air.
- 2) Moisture is necessary for the spores to begin growth. It can either be in the form of extremely high humidity that raises the moisture content of the wood over time (in a poorly ventilated crawl space under an elevated wood floor, for example), or lumber that has not been sufficiently kiln-dried at the factory to reduce the moisture content to under 20%, or water soaking into the wood surface.
- 3) Warm air temperature is also necessary for wood rot to flourish, although it possible for it to grow at temperatures down to nearly freezing.
While warm temperature is a component, the main trigger for wood rot to begin is moisture in the wood. The number one type of defect we see that causes rot at exterior wood siding and trim is any surface that allows rain water to puddle on the wood without draining or to seep into any openings between pieces of wood. This is called a “water trap” by builders, and a good craftsman works to make sure than any horizontal surfaces, such as window sills, have a slight slope to the outside so that no water puddling occurs, along with carefully caulking around windows and trim to seal out wind-blown rain out. Maintaining paint as a barrier on the surface of the wood is also important.
If you find areas of wood rot on the exterior of your home, be sure to repair the area in such a way to eliminate any future water traps. Also, rot at the bottom of plywood exterior siding is often due to splash-back of rain water off the ground from a roof overhang above. The worst location for splash-back areas of rot is where the roof drains onto a patio or driveway, and the best preventive measure is to install a gutter system over the area.
Another location where wood rot can develop is in the attic at leaking roof penetrations, such as in the photo at the top of the page of the roof sheathing below a leaky chimney flashing. Landscape sprinklers that regularly spray on the wood trim of a house can also accelerate rot, like in the photo below.
A wood rot inspection begins with a visual scan of wood surfaces, looking for any discoloration, sunken areas, and locations of previous repairs. The SitePro inspectors uses a probing device, such as screwdriver or knife, to locate soft spots in the wood surface indicative of rot. Then an electronic moisture meter may be used as follow-up, to see if there if the wood is currently wet.
An experienced inspector knows that there are certain locations that are more likely to have wood rot than others, and probes those places carefully even if there is no visible evidence of a problem. Here’s examples of nine areas that get special attention:
- 1)Wood fascia and soffit - especially at corners, as in the photo above.
- 2)Window sills - The top face should slant downward away from the way of the home but, as the paint deteriorates, this is an early area to get spots of rot growth.
3)Window and door trim - Water seeping into the joint between two pieces of trim has caused the damage below.
4)Bottoms of corner boards at siding - Although this is an example of advanced rot, if the bottom of the corner boards is not painted at time of construction and there is splash-back from rain falling on the ground close below it, most corner boards will develop a half-inch or so of rot at base within the first five years after construction.
5)Any wood around a chimney or other roof penetration - Any roof penetration is a good candidate for wood rot in the sheathing around it if the flashing is not installed properly or maintained, but chimneys are especial prone to leak as the flashing ages.
6)Bottom of plywood siding near the ground - Caused by splash-back of rain from the roof overhang above the siding
7)Underside of wood flooring around toilets, bathtubs, and showers in an older home with elevated wood floors and a crawl space - Small plumbing leaks that go unnoticed can create big problems in the floor structure below.
8)Base of porch columns - Bottom of wood columns that are in contact with the porch floor will suck up the moisture of any standing water around it. In this case, a sprinkler head nearby was also spraying directly on the wood.
9)Wood decks - Because of direct exposure to the weather, a wood deck has a 15 to 20-year estimated useful life at best. But when the deck is built close to the ground, as in the photo below, the lack of ventilation between wood and ground allows high humidity from ground moisture to buildup underneath and speed up the process.
Most of these locations are called “water traps” in the construction industry, meaning that they allow water to settle on the surface or to seep into a joint.
Van Hibberts, CMI
Certified Residential Building Code Inspector ICC-5319905
IBHS Fortified Certified Inspector #FEV32561020109
ARA Certified Inspector #20302 (Applied Research Associates)
Florida-State Certified Master Inspector Lic. #HI 89
Certified Owens-Corning Roof Data Inspector
Florida-Certified Wind Mitigation Inspector
WDO Certificate #JE190791
362 Gulf Breeze Parkway, #214
Gulf Breeze, Florida 32561
850.485.3209 (Cell / Text Msg)
"Looking Beyond The Obvious"