Homework: Preventing wood rot

1. Newer wood is more prone to wood rot

Wood rot has been on the rise for quite some time when it comes to wood trim on homes. There are several reasons for this, such as poor building practices, but a major cause has to do with the wood itself.

Much of the wood used today for trim on homes comes from hybridized trees that grow fast. The wood that's added to a tree in the spring has a much less dense structure than the wood added in late summer as growth slows. This springwood is the light band of color you see at the cut end of a long board or a log. The dark band is called summerwood. The two bands add up to a year's worth of growth. Cut into a piece of trim wood on an older home and you'll often see that the dark grain accounts for nearly 50 percent of the wood mass. In today's lumber, it can be less than 25 percent.

The fungi that eat wood feast on the easier-to-eat light-colored springwood. That means the hybridized trees simply can be consumed faster and easier by rot. That's why many owners of newer homes are seeing an explosion of wood rot.

2. Keep it dry

The easiest way to prevent wood rot is to keep wood dry. Fungus and fungi spores are just about everywhere. Since you can't stop the rain, you have to resort to making the wood think it's dry. One way, and this is where building practices come in, is to paint the wood on all surfaces and edges. This effectively puts a defense shield up so that water can't touch the wood. It takes more time and effort to paint wood in this way, but it does help.

3. Boron is effective

You also can pretreat raw wood that's dry with water-soluble borate chemicals. Boron is a very effective wood-rot prevention chemical. It's safe for humans and mammals, but the fungi that cause wood rot find it distasteful and poisonous. These borate powders readily dissolve in water. You can spray the solution onto lumber, but it's best to soak each piece in a trough of heated solution for a minute or so to allow the borate chemicals to soak into the end grain like a milkshake going up a straw.

4. Dry, dry, dry

Once the lumber is treated with the borates, allow it to dry. It's best to do this in the shade and be sure to separate the pieces of lumber with thin strips of wood so air gets to all the surfaces.

5. Prime and paint

After it's dry, you can prime it on all surfaces and edges. Then you paint all surfaces with the finish paint. If you cut the lumber to fit, the cut edge needs to be painted before it's installed. You can see this is very time consuming, but it absolutely works.

6. Saving some

If the wood rot has not progressed too far, it often can be repaired with long-lasting epoxies. There are some wood-repair products that act something like the borate chemicals. Rotted wood that you might cut away can sometimes be saved with a stabilizer that's brushed or poured onto the wood. These chemicals soak into the wood, giving it new life.

7. Overhangs prevent contact

If you're building a house, make sure the roof has generous overhangs. Keep at least 12 inches of separation between wood and the soil at grade. Use gutters and downspouts to prevent splashing of water onto the sides of a house. Use felt paper or an approved equivalent to make sure water never touches wood framing or sheathing. Don't allow masonry to come into direct contact with wood. Leave a separation of at least a half an inch to allow for air to dry the wood. And use flashings to direct water away from wood and to get water outside where it belongs.