How to Treat Wood Rot & Prevent Spreading

Wood rot can be nasty and early treatment is key if you want to save your timber or plywood from further damage. You’ll know if your wood is rotting if you’ve spotted dark spots, sponginess, decay, crumbly patches, fungus growth, shrinkage, and/or a damp smell.

Generally, wood rot cannot be saved, but it can be treated to remove the fungus and prevent spreading. If you have rotting wood, it’s important to take immediate action to prevent costly replacement work or repairs. Keep reading to learn what causes wood rot, how long wood rot takes to spread, and how to stop wood rot infections from spreading.

Can Rotting Wood Be Saved?

Whether rotting wood can be saved depends on if you have dry rot or wet rot, and how severely the wood has been affected. 

Wet rot is the most common type of wood rot. It is caused by water exposure, like leaks, condensation, penetrating damp, or rain exposure. Symptoms include the wood becoming soft, weak, faded, or boded. Treatment of wet rot is best reserved for areas like decking, sheds, outdoor posts, or exterior timber. Wet rot treatment is quick and easy.

If plywood sheets or unused timber have been affected by wet rot, you can still use it once it’s dry, provided the structure hasn’t been weakened. Wooden furniture infected with wet rot can sometimes be salvaged, depending on the type of wood used and how severe the damage is. When damp penetrates wood glue, furniture may dry warped and stained.

Dry rot is a much more serious fungal infection that attacks susceptible wood, like wood exposed to moisture and air simultaneously. You’ll usually find dry rot on window frames, floorboards, basement subfloors, or attic timbers. Dry rot in wood will almost always need to be cut back, spot-replaced, and sterilized to remove the infection entirely.

Can Dry Rot Be Stopped?

Yes, dry wood can be stopped, but fast action is needed, as it can spread quickly and cause severe damage to the structural integrity of a building. Dry rot treatment isn’t a simple task and will usually be costly, but it’s necessary to prevent irreparable damage.

How Do You Stop Wood Rot From Spreading?

The most effective way to stop wood rot from spreading is to fix the problem that’s causing the wood to become wet. For example, by fixing the leak or ventilation issues that are causing the wood to become damp. Damp wood in a property can be dangerous, especially if it hasn’t been treated after exposure. 

How to Treat Wet Rot

Wet rot is easy to treat and fix. Because it’s usually caused by a leak or bad weather, rather than a fungal infection, it doesn’t continue spreading after the source of moisture has been eliminated. Usually, stopping the source of moisture and applying a fungicide treatment to the wood, like borax, is a suitable remedy to prevent dry rot from forming.

However, wet wood cannot always be saved, especially if it has rotted. You’ll need to cut back and replace any rotted parts with new wood. For example, rotten wood frames around exterior windows[1] will need to be removed, replaced, and re-treated with a water-repellent finish, like epoxy or polyurethane.

How to Treat Dry Rot

Treating dry rot is best conducted by a professional. The infection can be severe and it’s tricky to identify how far it has spread. Treatment can vary depending on the severity.

Before deciding on your treatment plan, arrange a dry rot survey. During the survey, a professional will inspect the issue to identify its source, where the rot has spread, how it can be treated, and how much repair work should cost.

A dry rot survey can cost up to $500 in the US and it’s worth the investment. Even if you have already confirmed the presence of dry rot on your property, getting a survey is worthwhile, especially if you want to carry out the repair work yourself. Here’s how to stop wood rot after the fungus spores germinate.

1. Identify infected timber

Firstly, you need to identify the infected timbers. Look out for symptoms of the following in all surrounding wood:

• White, fluffy mycelium and brittle strands
• Mold that appears like grey-whitish skin, with lilac-yellow patches
• Soft mushroom-like mold, usually orange or with a rusty-colored center, and extremely wide pores
• Red dust, often close to a mushroom-like spore, with a brown appearance
• A musty smell or mushroom-like smell

2. Locate the source of the moisture

Next, you need to find the source of the moisture. This is important, as you need to fix the issue before treating dry rot. You may need to remove all nearby flooring, floorboards, plaster, masonry, and render to identify where the moisture is coming from. It’s best to seek professional help to identify dry rot, as some symptoms can be easy to miss without an experienced eye.

3. Complete a dry rot survey

Depending on how far the mold has spread, removing dry rot can involve cutting back significant parts of your home’s structural support beams. A dry rot survey will confirm the presence of dry rot and identify how it can be effectively treated, without causing an issue to the structure of your home.

4. Cut back infected timber

Dry rot is untreatable. All affected timber needs to be cut back, or removed and replaced with new, pre-treated wood. Use caution when carrying out these repairs yourself to ensure you don’t cause structural damage to your property. Once the affected wood has been removed, all the visible spores need to be cleaned and disposed of appropriately.

5. Sterilize surrounding walls

Next, walls need to be cleaned of the wet rot fungus. A stiff brush can be used to remove all the rot fungi and fruiting bodies. Always wear protective gloves, goggles, and a respirator mask when removing fungal growth. 

Once the visible areas have been cleaned, all surrounding walls and masonry need to be sterilized with a dry rot treatment, like a fungicidal microemulsion spray or injection. These treatments penetrate the substrate and kill the fungus. Any rot stains need to be removed before repainting. Dilute chlorine bleach and water and apply generously to the walls.  

Will Vinegar Stop Wood Rot?

Because white vinegar is a naturally acidic fungicide, it can be used to stop wood rot and prevent spreading. Vinegar can target minor wood fungus and kill spores by restoring the wood’s pH level, which removes the infection.

Before applying vinegar to wood, it’s important to treat the source of moisture first. For example, if you have a leak or penetrating damp, this needs to be fixed beforehand. Otherwise, the vinegar will not work as intended and the rot will continue to spread.

You also need to ensure the wood has completely dried before application. Use a humidifier to speed up this process. Then apply the vinegar using a paintbrush or lint-free cloth. Apply generously and evenly to the affected area.

Because vinegar is acidic, it can cause discoloration of the wood or corrode any wax product off the surface. If this happens, you’ll need to finish the wood to make it look nice.

Here’s how to apply vinegar to wood to stop rot step-by-step:

1. Fix the source of the rot e.g., leaks or penetrating damp
2. Dry the wood entirely
3. Apply the vinegar evenly and generously using a paintbrush or cloth
4. Allow the vinegar to dry fully
5. Refinish the wood as needed

You can use vinegar to stop wood rot on plywood, timber, and wooden furniture. It can also be used on exterior wood, like outdoor posts, sheds, and decking, but there are more effective solutions, like applying a water-repellent wood hardener or borax. 

Does Bleach Kill Wood Fungus?

No, bleach will not kill wood fungus caused by wet or dry rot. Being a corrosive substance, bleach works well when removing mold or fungus from any non-porous surface, like flooring, tiles, sinks, and bathtubs.

However, when used on wood, it may remove the fungus on a surface level, but it will not penetrate the infection deep enough to remove it entirely. This makes it an ineffective treatment that will leave your wood rot continuing to spread. There are more effective ways to kill wood fungus, like using white vinegar or borax.

Does Wood Rot Keep Spreading?

Yes, left untreated, dry wood rot will spread. This is because the fungus spores continue to generate moisture as they digest the rotting wood, so the dry root will spread until it has infected the entire area.

Once it’s spread, dry rot can be significantly difficult and costly to repair, especially if it’s part of a building’s structure. Because of how powerful the fungus is, it can even penetrate through materials, (like carpet or vinyl flooring), brickwork, masonry, and walls, making its spread even more detrimental.

On the other hand, wet rot will not spread as dramatically as dry rot. Provided the source of moisture is halted (like a leak), the wet rot should stay in the affected area, with only minor spreading as it dries. Because it isn’t a fungus, wet rot won’t consume the entire wood in the same way dry rot can.

How Long Does It Take Wood Rot To Spread?

Dry rot can spread quickly in the right conditions. Once the wood has experienced dampness, it can take around 7-10 days before dry rot spores begin to appear. Once formed, low temperatures and poor ventilation can cause the spores to spread very quickly. Generally, in conditions between 66-70 °F (18-21 °Celsius), dry rot can spread up to 80mm (8cm) per day.

What Happens If Wood Rot Is Left Untreated?

Damp or wet wood should not be left untreated. If you’ve experienced plumbing leaks, the surrounding wet wood should be left to dry fully before being treated with a wood preservative, like borax. When damp wood is left untreated, it can develop a fungal infection, like dry rot. 

Dry rot is a wood-destroying fungus that can rapidly spread around the structural beams in your home. It is easy to prevent, but difficult and costly to treat once it’s spread, so prevention is key.

Does Wood Continue To Rot After It Is Dry?

Rotted wood will not spread when the source of moisture has been removed. For example, if you had a leak in the attic that rotted several timbers, fixing the leak will prevent further rotting. However, the surrounding wood must be treated after it’s become damp to prevent dry rot from occurring. 

Dry rot fungus spreads quickly, even when the source of moisture has been removed. If dry rot has already formed in the wood (see above for a list of symptoms), the infected wood will continue to rot until it is treated. This can weaken the wood’s structure, which can cause roof defects. 

Summary: Things to Remember

• It is easy to prevent wood rot after a plumbing leak by applying a wood preservative to affected areas
• Damp or wet wood is still usable, provided it hasn’t boded, but it needs to be treated with borax to prevent dry rot from forming
• Rotten wood, like wood around a window frame, cannot be repaired and needs to be cut back and replaced
• Act fast after spotting dry rot in your property to prevent spreading
• Left untreated, dry rot can cause severe, costly structural damage
• Identification and treatment of dry rot is best carried out by a professional to ensure further damage is minimalized