Stop Wood Rotting

What to put on wood to stop rotting?

In nature, wood rot is a vital decomposition process, turning fallen logs into nutritious soil. But few things send homeowners into a panic as quickly as discovering it their homes, because wood rot can lead to a number of structural problems, including deteriorated support posts and beams, rotted floor and ceiling joists, and destroyed roof decking. The cost to repair the damage—or, in other words, replace the rotted wood—can run in the tens of thousands of dollars.

Because wood is the most prevalent building material, it’s essential to understand what causes wood rot, how to prevent it, and what to do if you discover it—discover being the operative word, as wood rot is often hidden from view beneath flooring, wallboard, and siding. Read on for the must-know info.

There’s a difference between rotted and rotting.

One of them means it’s probably too late, the other means it’s more salvageable. There are ways you can save tons of different wood, regardless of their weather exposure.

The most common that’s seen is dooring and roofing. Water wreaks havoc on anything made out of wood, and for more reasons that mould or rot.

It forces the wood fibres to expand and contract past the point of what it normally would.

When wood is gathered from trees, there’s what’s known as a 100% moisture content in that wood already. However, when you add water, that’s completely different.

Moisture exposure wrecks wood, so how do we fix it?

There are some tips and tricks here to salvage almost any rotting wood, and a full checklist to determine if that’s the problem you’re facing.

If water gets into cracks and under painted surfaces and doesn’t dry out, it can cause wood rot. Once it takes hold, your only options are big-buck repairs and replacement of the rotted parts.

Left untreated, wood rot may spread, infecting other wood parts and possibly leading to structural damage.

That’s not all: The dampness that causes wood rot invites voracious termites. Bottom line: Because your house is made with a lot of wood — framing members, plywood sheathing, trim — there’s a lot to protect.

At Hitch Property Constructions, we offer timber repairs work from simple timber repair to almost new structures, renovations, and extensions.

Why Does Wood Decay? Where Does It Go?

Did you ever wonder what’s going on, with wood being there, and then in a few or many years it’s going away, and becoming weaker, and finally gone? Small Life is eating wood. Here’s how it happens:

The life forms on this planet may be generally divided into two basic groups, animal and vegetable. The vegetable (plants, broadly speaking) forms are characterized by the ability to absorb from sunlight the energy they need to live, grow and multiply. They provide the power (food) for all Life on earth as it is only they that capture energy from the sun.

The animal life forms are characterized by their inability to absorb light energy from sunlight, although these definitions are simplified. Vegetable life forms are generally rooted in one place, whereas animal life forms are generally capable of movement. A mushroom is rooted in one place although it does not absorb sunlight for energy, relying instead on the energy content of its food. In recent years the scientists who classify things have decided that fungi are different enough from plants that they should get a third, separate category. Life forms now are “animal” and “vegetable” life forms, some of which are called “plants” and some called “fungi”. We are not going to get any more complicated than that, except to note that anything that does not capture energy from the sun (i.e. is a plant ) gains its energy from eating something else. This is the ‘Food Chain’.

Wood rot is a form of decay triggered by the combination of moisture and fungi (microscopic organisms). For fungi to set up shop, the wood must be continuously damp; fungi will not grow on dry wood. Yet as many as 5 million types of fungi exist in the air and soil around us, and there’s no escaping them. While many types, such as yeast and mushrooms, are beneficial, others are destructive. The numerous types that trigger wood rot are loosely classified by the three general effects they have on wood.

  • Brown Rot: Often called “dry rot” because the surface of the wood appears dry, brown-rot fungi targets cellulose in the wood’s structure. As the cellulose is destroyed, the wood shrinks turn deep brown and break into small cube-shaped bits—a process known as a cubical fracture. Brown rot thrives at temps between 65 and 90 degrees Fahrenheit, and once it starts growing, it spreads rapidly.
  • White Rot: If wood takes on a whitish or light yellow shade and feels spongy, it’s probably white rot. Whereas brown rot affects cellulose white-rot fungi break down lignin, another element of the wood’s structure, leaving the light-coloured cellulose behind. Like brown rot, white rot occurs in temps between 65 and 90 degrees Fahrenheit.
  • Soft Rot: Soft-rot fungi decompose wood more slowly than brown-rot fungi and white-rot fungi, but thrive in temperatures too hot and too cold for the other types to survive, between 0 and 110 degrees Fahrenheit. Soft-rot fungi break down cellulose, leaving the wood with a honeycomb-like appearance, and while it is usually found in fallen logs and trees, not commonly in houses, it can strike a home if conditions are right.
Stop Wood Rotting

Where Is My Home at Risk?

Because wood rot occurs in damp areas that do not dry out, it often goes undetected until a remodelling project exposes it. The following areas are the most likely spots for wood rot to get a foothold.


Today’s windows are designed to prevent leaks, but all it takes is a small gap that’s not adequately sealed with caulk for the rain to seep through and saturate the wood in the wall beneath the window. Because the wood is not exposed to air or sunlight, it remains damp—providing optimal conditions for fungi growth. Older wooden windows are at even greater risk, as water tends to pool on the horizontal sills, seeping through cracks in the paint.

Exterior doors

Like windows, cracks and gaps between a door and the siding (or threshold) permit water to enter, making them prime spots for wood rot. The rot is often found when homeowners decide to install a new door. Once the old door frame is removed, the rot is visible in the wood framing.

Outdoor decks

Horizontal decking boards and stair treads can also hold water. While many treated decking boards are water-resistant, they’re not 100 per cent waterproof, and over time, they can rot. The bottoms of painted balusters are a prime spot for rotting; they’re typically built from untreated pine, and then painted to resist the elements. Water becomes trapped under the bottom of the baluster and doesn’t dry out, giving fungi a chance to grow.


High humidity and moisture are prevalent in basements because the concrete walls are surrounded by moist soil. Humidity levels can be so high in leaky basements that water vapour can form on the surface of walls and wooden ceiling joists. Once wood rot gets a foothold here, it can spread unnoticed until it creates structural damage.

Wet rooms

Any room with a plumbed water fixture, such as a kitchen, laundry room, bathroom, or utility room (with a water heater) is at risk. Leaks around water supply lines and drain pipes keep the area wet and provide an optimal environment for wood-rot fungi to thrive.

Damaged roofing

Missing or damaged shingles can permit water to seep in, and over time, it can lead to wood rot in the roof decking and in the lumber used to frame the attic.

How Do Bacteria Work? How Do They Cause Rot In Wood?

Bacteria are a different kind of Life than fungi, but still a microscopic single-cell life form. They are more like an animal than a plant, some more like a fish and some more like an air-breathing animal. There are many thousands of different kinds of bacteria, and many of those will also make spores when the region dries out.

What Do Bacteria Need To Keep-Alive

Bacteria tend to prefer the wood damper than do fungi, but there is a humidity range where both can live. Many bacteria can survive drifting through the air until they contact a wet surface. Some bacteria live completely immersed in water. Most bacteria can move about. Some wiggle, others have many small legs they use to crawl about with or to swim through the water in search of food or company.

Check out our range of timber repairs Melbourne at Hitch Property Constructions. 

What About Our Wood? The Food For These Organisms?

Wood is said to breathe because the natural humidity of wood, perhaps five to fifteen per cent (once it has sat around in your garage for six months) can go up and down a bit as the humidity of air varies. The air humidity ranges from maybe ten per cent in a dry summer to perhaps ninety-five per cent in humid summer.

Humidity (of air) means how much water vapour is dissolved in the air. Ten per cent humidity means the air is holding ten per cent of its maximum capacity. Ninety per cent atmospheric humidity means that the air has dissolved in it, ninety per cent of its capacity. At one hundred per cent humidity it is raining.

The humidity of wood is usually expressed as a per cent (for example, ten per cent). This means the percentage by weight of the wood that is water. In the case of air, the humidity is not the percentage by weight of the air that is water, but rather the per cent of capacity. The capacity of air is about one per cent water by weight, and it varies a lot with air temperature.

Wood holds a little water very strongly and more water with less strength and even more water rather casually. When there is less humidity in the air, wood loses some of its water to the air by evaporation. When atmospheric humidity is high, damp wood may lose some of its water, but dry wood will capture some water from the air. This movement of moisture in and out of wood is what is meant when the wood is said to “breathe”.

Moisture Content Affects The Woods Physical properties.

The small branches of plants are very flexible because the wood is full of water. As the wood dries out, it becomes stiffer. Old wood found in the desert or a dead branch of wood may be quite brittle.

Wood placed in a box and exposed to the hot steam from boiling water becomes flexible, almost “rubbery”, and can be bent into a new shape. Held in that shape as it cools and dries back to its natural humidity at room temperature, it holds the new shape. This “steam-bending” process makes the curved ribs for many small boats.

Wood Is Hollow, and It Has Space For Water And Organisms That Cause Rot

If you put a piece of wood in water, it floats about half-above the water and half-below. This shows that wood is less dense than water. Wood is about fifty per cent space inside, but that is before wood rot starts. More deteriorated wood in water becomes “waterlogged”. In this condition, water has gotten into most of the space inside the wood, and it floats with less of its volume above the water, or may even sink when there is not enough air space left inside the wood. You may have seen waterlogged wood on the bottom of a pond, or handled waterlogged or damp wood and noticed how much heavier it was than dry wood.

Stopping moisture that causes wood rot

In some cases, it’s clear that a leak or drainage issue is the cause of excess moisture that’s leading to rot. Other times, the culprit is less clear. Until you’re able to figure out the cause of the water, it’s often hard to predict the extent of the rot damage.

How to kill the fungus that causes wood rot

Boric acid (borate) is one of the most effective fungicides for use in treating wood rot. It can be applied to wood during construction to prevent future rot, or as a treatment to stop an active decay fungus from growing.

Can wet wood rot be repaired or treated?

Wet rot is often less damaging than dry rot. Typically, when you eliminate the source of moisture, the rot stops spreading. Once the moisture is eliminated, applying a fungicide like borax will help ward off future wet or dry rot.

When wet rot has affected small, easily accessible, non-support areas, you can typically remove the damaged wood and rebuild it with wood filler. Once rebuilt and sealed, your wet wood rot is successfully repaired. If the wet wood rot has affected a larger area or an area of wood that is load-bearing, the timber needs to be replaced.

Can dry wood rot be repaired or treated?

Dry rot is more difficult to repair than wet rot. Because dry rot can spread quickly through the wood and even porous masonry, it’s incredibly important to eliminate all stages of dry rot fungus immediately. The most effective way to do this is to remove and replace all affected wood and treat the timber in close proximity with a fungicide.

Can I Treat or Repair Rotted Wood?

Softwood damaged by wood rot is not salvageable and should be replaced as soon as possible to keep the rot from spreading. If the wood is discoloured, but the screwdriver test did not detect softness, you can try treating it. You’ll first have to dry the wood by repairing leaks and running a dehumidifier. Once the wood is dry, you can apply a wood preservative that contains copper or borate, such as Woodlife Copper Coat Wood Preservative (available on Amazon). Monitor the wood because it’s still at an increased risk of future rot.

How Can I Prevent Future Problems?

When it comes to wood rot, prevention is the key. It’s easier—and much cheaper—to prevent rot rather than fix it. The following steps will help keep the wood in your house dry, so fungi don’t have a chance to set up shop.

  • Seal all cracks around exterior doors and windows with caulk.
  • Scrape away old hardened caulk, and replace it with fresh caulk.
  • Clean gutters regularly—at least twice a year—to prevent blockages that can lead to water running over the backside of the gutter and down the side of your home.
  • Add a covered entryway over doors to keep the rain away from the doors.
  • Use a good dehumidifier in the basement or any room of the house subject to high humidity.
  • Install exhaust fans in bathrooms to remove steamy air caused by hot showers.
  • Repaint exterior windows and siding if the paint is cracking or peeling.
  • Sweep standing water from outdoor decking as soon as the rain stops.

We have a wide range of Melbourne timber repairs for your home renovations. Check out Hitch Property Constructions.

How Much Rot Is “Too Far Gone”?

If it’s soft to the touch (wet rot) and you can remove wet wood gunk with a simple pass of your hand, then it’s not likely to be salvageable.

If your wood has rotted over about 20%, then you have a tough choice to make.

You can either remove the rotted part and salvage what is left of the board, even though it will be smaller, or you can replace it.

When rot moves through the wood instead of manifesting in one corner or area, it makes the damage harder to detect, and likely worse than first anticipated.

Apply any of those previously mentioned methods, and you’ll be able to either fix your lumber or at the very least stop the spread of wet and dry rot.

Once you’re done, be certain that the wood is properly sealed and treated to prevent this from happening again.

It’s hard to prevent wood rot, but with these provisions, it makes it a little bit easier.

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