What is Wood Rot and How to Stop it?

As the owner of two companies, Austin Historical and Preservan Orlando, that employ dozens of people in the fight against wood rot. In the humid south it is a full time job that really never ends. 

Wood is an amazingly versatile building material. It can molded and shaped to almost any form. It is an excellent insulator. Its structurally abilities are incredible. Its ability to accept paint, stains and varnishes is fantastic. Its one weakness is rot.

In this post, you’ll learn how to identify rot, how to fix rotted wood, and most importantly how to prevent rot. That everything you could need, right?

Wood rot is caused by only one thing and I’ll get to that in just a moment, but first, there are 4 conditions that must be present in order for rot to occur. Remove any one of these conditions, and you stop rot in its tracks.

4 Conditions That Rot Requires

1. Substrate (Wood)
2. Oxygen
3. Warmth
4. Moisture

For you northerners, freezing temperatures slow down the rate of rot, but it doesn’t stop it completely. Since we don’t have much control over any of the conditions except moisture, that’s where we’ll focus our energies.

What Causes Rot

Wood rot is caused by fungi. The simplest of all plant life. Microscopic fungus spores are all around us floating on the breeze and landing all over our homes. Wherever they land, if the four conditions above are present, then you will have rot and that rot will continue as long as those conditions are present.

Even if you remedy the conditions, the fungus is still present and will resume growth (aka rot) when the conditions are more favorable.

Types of Wood Rot

Identifying different types of wood rot involves observing specific characteristics associated with each type. There are two main types of rot most homeowners will deal with below.

Dry Rot

• Color and Texture: The affected wood may become lighter, taking on a white or greyish color. The wood may also have a cubical cracking pattern, resembling small, rectangular pieces.
• Fungal Growth: Dry rot is often accompanied by a distinctive fungal growth with a silky sheen. The mycelium can appear white or grey and may spread across surfaces.
• Musty Odor: Dry rot is associated with a musty, damp odor.
• Shrinkage and Brittleness: Infected wood tends to shrink and become brittle, losing its structural integrity. Look for the characteristic cubical cracking pattern in the affected wood.

Wet Rot

• Color and Texture: Wet rot may cause the affected wood to darken and become softer. The wood may take on a darker, more spongy appearance.
• Fungal Growth: While wet rot can produce fungal growth, it may not be as distinct as the growth seen in dry rot. It can vary in color and texture.
• Moist Conditions: Wet rot thrives in consistently damp conditions. Identifying and addressing the source of moisture is crucial.
• Localized Impact: Wet rot often affects the area where moisture is concentrated and may not spread as extensively as dry rot.

How to Prevent Rot

So, how do you stop wood rot? Well, you can always remove wood from the equation, but for most of us, that would mean removing our entire house.

And here on earth, there isn’t much we can do about eliminating oxygen or warmth. On a side note, the lack of oxygen is why wood that is submerged underwater for decades or centuries can remain in completely pristine condition.

The organisms that cause rot need oxygen to survive and the underwater environment is decidedly oxygen free. The city of Venice, Italy and the famous Brooklyn Bridge are a couple examples of structures built of wood foundations that have survived hundreds (in Venice’s case, thousands) of years with very little wood rot.

Back to how to stop rot. If we can’t get rid of wood, oxygen or warmth, then the only thing we’re left with is moisture. So then, how can we stop the wood elements of our house from excess moisture which causes rot?

Eliminate the Moisture Source

Molecularly speaking, wood is designed like a bunch of straws that bundled together. Those straws carried water from the roots to the leaves when the tree was alive and they still carry water when the wood has become a part of your house after its death.

That means that area most prone to begin rotting is the ends of wood where the end grain is exposed. The end grain acts like a sponge soaking up water into the wood which begins the rot process. If you can shut down the sponge and seal up that end grain then you at least have a fighting chance against rot.

There are a few things below you can do to help the wood not suck up water or dry out if it does get wet.

1. Keep it Painted – Keeping your house painted is the easiest way to keep the water out. Paint is a great layer of protection to help the surfaces of your house shed water and dirt. Though it may get wet, the paint keeps the water (and fungus) from attacking the underlying wood.

2. No Standing Water – If any part of your house gets standing water after a rain storm, then that area is much more likely to rot. Standing water will find its way into joints and cracks in the paint and seep into the wood giving rise to perfect conditions for rot. Redesign these elements to allow water to shed off of them.

3. Allow For Air – Good airflow helps everything dry out faster, and the faster things dry, the less chance of rot. Trim back shrubs and trees from your house so that there is a enough room for some airflow between the two. Wet shrubs directly against siding are a major cause of rot on many houses.

4. Seal End Grain – Before painting slather an exterior yellow wood glue like Titebond III onto the end grain to block the uptake of water. Apply it right from the bottle for softwoods, but for hardwoods that are more dense and slower to soak in you can mix it with up to a 50/50 mix of water before applying. Thoroughly cover the end grain and let it dry before priming and painting the wood as usual.

5. Adjust Sprinklers – If your sprinklers are constantly spraying any wood on your house that will be ground zero for wood rot. Check and adjust them annually to make sure they are watering just the plants and not the house.

6. Clean Gutters – Gutters clogged with leaves get back up causing water to overflow into soffits which causes all kinds of problems. Make sure you clean your gutters regularly to avoid rot on rafter tails and soffits.

If you can keep it dry, you’re leaps and bounds ahead of the rest of us. Yes, the cause of rot is fungus, but if you focus your energies on keeping the exterior surfaces of your house dry you’ll stop rot in its tracks. And preventing rot is a lot easier than stopping it once it really gets rolling.

Apply a Preservative

The main product that I use to treat rotten wood is also the same product that works great for preventing termites and other insects that destroy wood.

BoraCare is a borate treatment that is easily applied to bare wood and over time it migrates throughout the entire mass of the wood. It doesn’t just sit on the surface, but treats the whole thing making the wood unappetizing for insects and uninhabitable for fungi.

A borate treatment can both be used as a preventative treatment or as a remediation to kill an existing wood rot problem in varying concentrations.

How to Fix Rotted Wood

If you’re already dealing with a wood rot problem then I’ll walk you through a few steps to help you fix rotted wood and get things back in line. A common misconception is that you don’t have to replace big pieces of wood if it is rotten. If the rot is localized there are inexpensive ways to repair just the damaged sections.

1. Remove Loose Wood – Any wood that has been completely destroyed by the rot needs to dug out using a wood chisel or similar tool. scrape, chip, or cut away the damaged portions until you get back to solid wood.
2. Treat With a Borate – Apply a borate to the area to kill any remaining fungus and let it dry according to the manufacturer’s specifications (usually 48 hrs.)
3. Apply Wood Consolidant – Once the wood is completely dry, apply a couple coats of a product like Abatron LiquidWood to the affected areas to consolidate and strengthen the wood fibers. This acts as a primer to prepare for the next step.
4. Apply Epoxy Filler – Using an epoxy filler like Abatron WoodEpox fill in the damaged areas and shape the epoxy to match the profile of the wood as closely as possible.
5. Sand, Prime, Paint – Once the epoxy has cured you can sand it to blend in the repair to the best of your abilities and then be sure to seal it with a coat of primer and two coats of exterior paint.

Using a wood epoxy for these repairs is a far better option than using a traditional wood filler because wood epoxies will bond to the wood better and move with the wood throughout seasonal changes unlike certain wood fillers.

Epoxies can also be used to rebuild whole sections of wood and even be used for structural members like framing and columns making them an all-purpose option for fixing rotted wood.

If you’ve got a wood house go ahead and bookmark this page for future reference so you’ve got a great references for any kind of wood rot repair, prevention, and diagnosis in the future. You’re officially ready to stop wood rot in its tracks now!