How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
How does a home inspector evaluate wood rot?
Tuesday, August 14, 2018
A wood rot inspection begins with a visual scan of wood surfaces, looking for any discoloration, sunken areas, and locations of previous repairs. The inspector 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 followup, 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.
Although licensed termite inspectors are allowed by the State of Florida to probe wood that appears to be soft for evidence of wood rot or termite damage, there is a limit to how much wood they can dig into as part of their evaluation. See our blog post Is the WDO (termite) inspector allowed to poke holes in my wood siding and trim? for more on this.
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