Look out for “Deck Destroyers”
The two principal deck destroyers are surface damage (like mold) and deep damage (like rot and pests). Let’s look at them in turn:
Dealing with Surface Mold
There are four types of mold under the deck to look out for:
1. Black mold. This is mildew and can be seen as lots of black spots. It is fairly normal to see this. Sometimes, if the deck is very wet, the whole bottom of the deck boards is black. A spray of dilute bleach under the deck is a simple treatment to keep this under control.
2. White mold. This is a fungus called Mycelium and it is a sign that the deck is wet and staying wet. Often you see this where water “stands” where deck boards meet the joists. This indicates that a problem will appear in the next ten years. If you can reach it, it is best to pressure wash off the fungus and then kill it with dilute bleach.
3. Green mold. This is the worst rot and needs immediate attention. Usually it is a thin film of green mold, but it can get far worse within a few years. I have seen a deck covered in thick green mold under and on the deck; you could barely walk on it without your feet going through. Best to pressure wash off the green mold and apply chemicals to stop it coming back.
Dealing with Deep Rot and Pests
There are four types of deck board damage to look out for:
1. Dry rot. You will be familiar with this. This is rotting, usually first seen at the ends of deck boards as a softness and brown discoloration, often dampness. Replace the board when the end starts to get springy. Or you can use Copper Green chemical (very toxic, respirator needed).
2. Brown rot. This is quite rare, and is a cubic break-up of the wood. Treat with chemicals or replace the board.
3. Termites. When wood gets damp (such as, when the stain no longer keeps the water from entering the wood), termites can burrow into it. They tend to enter at the ends of boards and munch their way down the grain, then they find another board. Many people think they are like piranha but they are not that fast. Every house has termites; you just don’t realize it. There are different types of termites. Some fly around and then drop their wings and enter the wood. Others can make their own “ladder” and climb vertically upwards towards your deck! Look out for discarded wings, small brown wood particles pushed out of holes in the wood, or distinctive fungus-like vertical tubes under your deck. Treat with “Orange Oil”, tent the deck and house with chemicals for 3 days, or have a pest-destroyer come along with their microwave wand.
4. Beetles. Fairly rare, they leave a single pinprick entry point about 1/32 inch in diameter. Easy to miss. Usually not that destructive. Apply killing chemicals to entry point.
You can find more information and pictures in our handy pdf called “Deck Destroyers” from our website.