In the Nick of Time
If you're doing any repairs to wood on your home, building a deck, even building wood flower planters, always use pressure-treated lumber or lumber substitutes. Yes, they're more expensive, but they'll save you money in the long run.
The best time to prevent rot is when homes are built. Some wood used in home-building, such as Western red cedar and redwood, contains substances that make them naturally fungi resistant. But these fungi-resistant woods are in short supply,and are too expensive to be used widely.
Alternatives to these woods include
Pressure-treated lumber, which is impregnated with chemicals that protect it from insect and fungal damage. There are different types, rated for various placements: above ground, ground contact, and wood foundation.
Wood-polymer lumber, which bonds wood with fungi-resistant plastic.
Extruded plastic lumber made from recycled plastic containers.
Building on well-drained sites with proper grading will also help prevent wood rot.
In existing homes, periodic inspections can go a long way toward fighting off many problems, including wood rot. If you're picking up a musty smell in your basement or it's been raining more than usual, it's definitely a good idea to take a good look around.
Before you go, arm yourself with a pointed tool, such as a screwdriver, ice pick, or awl. You'll need it for probing suspect wood.
Inspect the following areas. Use the tool to dig into any suspicious areas. If it enters easily, you've got rot.
Exterior trim. Pay close attention to horizontal or nearly horizontal areas that don't drain well, such as window sills. Cracked, peeled, or blistering paint are signs of moisture damage. Be sure to check underneath exterior doors, too, as water often pools here.
Behind porches or patios. Wood here often sits close to the ground, concrete, or masonry. Rot can also develop in the wood behind concrete steps.
Interior crawl spaces. Pay particular attention to joints, which typically retain water longer than other areas.
If you have a fireplace, also check the flashing on the roof around the chimney, and the areas around the chimney (especially sub floors) where it runs through your home. While you're up there, check flashings around vents, skylights, around the roof—anywhere water can pool and cause problems.
How Dry Am I?
Around the House
If you have a friend who builds wood furniture or does other wood crafts, ask about borrowing a wood moisture meter. Serious woodworkers almost always have one, as wood that is too wet or dry can wreak havoc with their projects.
If you don't find rot, but you still think there might be a problem, get your hands on a wood moisture meter. These handy devices are available at many hardware and home improvement stores and at stores that carry woodworking supplies. They're not cheap—the low end is around $100 or so—but they're worth the price if they detect a moisture problem before fungi sets in.
Most moisture meters use electric impedance to test moisture levels. These devices have two little pins on one side. You stick the pins into the wood, then press a button or flip a switch. This sends a quick jolt of electricity through the wood. Internal circuitry measures how quickly the electricity makes the rounds from one pin to the other. Wet wood conducts electricity faster than dry wood does.
Other models are pinless and use electromagnetic radio waves to test wood density. The denser the wood, the wetter it is.