Wood Rot Around Windows and Trim: Causes, Prevention, and Fixes

When wood gets overly exposed to moisture, the conditions are ripe for wood fungus to begin to grow. Often referred to as dry rot, this process of decomposition is accelerated by continual exposure to damp conditions. The fungus feeds on the cellulose in the wood, weakening it and producing spores that spread to other nearby food sources—that is, more wood.

This process occurs over time as the fungus is allowed to grow. So, it's important to remove all the affected rotting wood as soon as you can—to stop the rot from spreading to other parts of your home.

How common is wood rot?

In the humid, seasonal climate of Georgia, wood rot is one of the biggest problems leading to window replacement. It's especially likely to show up on older homes with aging wood fixtures. But even on newer homes, many windows come with wood or wood-clad frames, sills, grilles and trim—all of which can be vulnerable to water damage.

Wood rot hinders your windows' performance

Because dry rot causes wood to lose its strength and shape, your windows won't perform as well as they should. As the decay progresses, it can cause the window frames and sills to shift out of position, creating gaps between windows and exterior walls.

This looks unattractive, of course—but worse than that, it exposes your home to the elements and allows drafty air to get in, leading to higher utility costs and lowered energy efficiency.

Plus, moisture infiltrates those gaps and weak spots, making it easier for leaks to occur, damaging your personal property and your house's overall structure.

What happens if wood rot isn't promptly addressed?

Like any form of decay or wear, wood rot will get worse the longer you allow it to occur. Left unchecked, the rot will spread to other areas in your home. Your house's underlying frame, support beams, eaves, roof underlayment, and more can begin to show signs of problems too.

Long-term, the result of wood rot is serious structural damage that compromises your property's safety. The worse the damage is, the more complicated and costly it is to make the needed repairs. And if you plan to sell your home, the compromised structure will negatively affect the asking price.

The good news is that homeowners can often detect the work of dry rot before it leads to more costly damage—as long as you know what you're looking for. As you examine your windowsills, frames, and trim, see if you notice these common symptoms of rotten wood:

Visible signs of rotting wood windows

• Warped, misshapen surfaces. Since dry rot is a form of decay, the wood it affects begins to shrink, crack, and develop grooves or holes. Windowsills, frames, and trim look broken, uneven, pitted—and unattractive.

• Leaks. As your wood windows break down, it becomes easier for moisture to get underneath siding and inside your house. This often shows up as streaks or stains beneath windows—either on your siding or on interior walls.

• Spongy feel. Decaying wood loses its hard, resilient surface and begins to soften as the dry rot progresses. You'll find it easy to strip pieces away or cause dents in the wood with a flathead screwdriver.

• Difficult operation. Windows that are rotting will stop functioning normally, and may not easily open, close or lock.

• Blistered, peeling paint. Because rot weakens the wood's surface, paint can't neatly adhere to it. As a result, that paint will wear away sooner than it should under normal conditions.

• Missing or broken caulking. As dry rot progresses, windows shift out of their tight position, causing caulking to be damaged.

• Discoloration. Moisture damage can make rotten wood look darker or a different color than other, healthier parts of the window frame. If parts of your wood windows look different, discolored, or darker than others—for no obvious reason—that's a sign of rot.

• Inefficiency. Rotten wood windows don't perform properly, so you may notice higher energy bills or drafts. To check this, hold a candle next to the window to see how badly the flame flickers.

Inspect your windows and trim regularly for dry rot

Using the signs above as your guide, walk around your home both indoors and outside, looking for symptoms of rotting. If you notice any of these issues with your windowsills, frames, grilles or trim, don't ignore them. Instead, have a professional window contractor perform an evaluation to identify the root cause and assess any dry rot.

Since dry rot can quickly spread to healthy wood and multiply, it's a good idea to act fast to make repairs. Here are a few answers to questions you likely have about fixing wood rot:

Can wood rot be repaired—without replacing the window?

Signs of rotting often appear first on a window's trim or sill. The issue may seem small, but it's not easy to judge how far the wood rot has spread at first glance. It's helpful to have a professional window company inspect your home to properly assess the problem.

Although some people prefer to make repairs by substituting rotten trim with healthy wood, our windows team strongly recommends full replacement of the entire window to ensure all the dry rot fungus is completely removed and can't spread.

Is there anything homeowners can do themselves to address wood rot?

The number-one rule of dealing with rot is that the damaged wood must be removed. While we recommend replacing your windows if rot is present, if you are certain the damage is isolated to a very small area, you can attempt a DIY fix, but it may delay the inevitable: wood windows will need to be replaced at some point.

What if wood rot is found during a window replacement?

If you're in the midst of a window replacement when dry rot is discovered, what happens next will depend on how much the rot has spread.

• First, our windows team will immediately inform you of any wood rot we find as we replace your windows.

• If the issue is isolated to one small area, we will simply replace the affected trim.

• If there is significant, widespread rotting, we'll provide you with a change order for the additional labor and material costs—so the rot can be eliminated completely.