Rotten Timber

How do you fix rotten timber?

Rotted wood is a common problem in most households, especially those who own older homes. Rotted wood is a result of moisture in the area or just being old, and it can happen both indoors and outdoors of your home. Most rotted wood appears in high moisture areas near water pipes, attics, basements, door jams, decks, and fences. Thankfully, there are ways to repair the rotted wood versus spending your time and money on replacing it the whole thing. 

Wood rots due to the presence of enough moisture for fungi to use the wood as food. The fungi damaged areas extend well beyond the visible rotten wood. Any rotted wood repair that is to last has to treat the wood that has started to rot but is not damaged, in addition to the wood that has started to rot.

Over time, wood will start to rot as it’s exposed to moisture. Not only is it unsightly, but it can also cause damage to your home if it’s left untreated. Luckily, rot is easy to remove and replace. Whether you choose to use epoxy, a wood filler, or another piece of wood to patch the rotted area, you can have your home looking good as new!

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

What You’ll Need

Rotten Timber


  • Putty knife
  • Rasp or utility knife
  • Wood chisel


  • Paintbrush and paint to match 
  • Sanding block or 100 grit paper
  • Polyester or Epoxy filler
  • Wood hardener


Evaluate the Damage and Diagnose the Problem

Inspect the area that you suspect rotted wood, see how much damage is there and how much repairing you will need to do. If the rotted wood is limited and not more than 50 per cent of the product, you can most likely repair the rot without professional help or replacement. Next, prevent this problem from happening again by figuring out what has caused this wood rot. Look for leaks, open spaces where weather elements and moist air can affect the area if it is outdoors considered checking your gutters and bad drainage areas.

Clear the Rotted Wood 

Using your rasp or chisel, remove the rotted wood carefully. This takes a gentle hand and the right amount of pressure. Be sure to get any spots that seem to be weak around the wood rot. Once removed, clean the area of any debris. 

Apply a Wood Hardener 

You can find a wood hardener at your local home improvement store. The hardener is a resin that will penetrate the wood and create a seal and will help prevent moisture from seeping in. Using a small paintbrush, slather on the wood hardener to the exposed area and allow it to dry.

Apply Filler 

Wood putty or epoxy is the best agent to fill the wood. Using a putty knife, apply the putty to the areas that need to be filled. Make sure that you smooth it and remove any excess putty quickly before it dries. Allow the putty to dry completely, overnight preferably. 

Sand It Down

Once the putty has dried, using a sanding block or sandpaper, sand down the putty to match with the surrounding wood area. Be sure to blow or wipe away with a dry rag any remnants of wood and dust. 


If you are planning on painting and depending on the area, you may need to prime the newly fixed area with a primer. Using a paintbrush and following the directions of the primer, apply and allow to dry completely.


Lastly, paint your patchwork! You may need to apply one to three coats depending on the results you are looking for. Allow drying and ta-dah completely! You are good to go!

Epoxy is made up of two components that harden when mixed. With a consistency like dough, it can be moulded by hand but will hold its shape as it hardens. It bonds well to timber and holds up against the weather. When dry, the filler can be sanded, primed and painted. And it also takes stain in a similar way to softwoods such as pine. Before staining, create fake grain lines by cutting into it with a utility knife. The timber-like illusion helps to disguise the patched-up work.

How to Restore Rotted Timber

STEP 1: Remove the rot

Probe with a narrow chisel or screwdriver to find damaged areas (rotten spots are noticeably softer). Rot often occurs under paint, so don’t assume it is sound because the surface looks good. Gouge or scrape away large chunks with a chisel.

STEP 2: Soak the timber

Apply timber preservative. Repeat until the timber won’t absorb any more (usually three to four applications). Wipe away excess. TIP: Drill holes into the area to improve penetration. Filling holes is easier with a nozzle squeeze bottle.

STEP 3: Apply the epoxy filler

Rebuild missing areas with epoxy filler. For deep holes, drive screws partly into the timber to anchor the epoxy. Smooth filler with a putty knife before it hardens, dipping the knife in epoxy solvent or lacquer thinner first to stop the filler sticking

Rebuilding wood

Protect timber from rain for a week or so before applying the epoxy. Rough up the timber with coarse sandpaper or a wire brush – epoxy sticks best to bare, rough timber. Paint exterior repairs within three days as UV rays degrade the epoxy. Soak severely damaged timber with liquid epoxy. Use a brush and squeeze bottle to push it deep into the area. Apply several times while the previous coat is still tacky.

Removing the Rotted Area

Claw out rotted wood out with a hammer. 

Use a claw hammer to dig out loose rot. Place the claw of the hammer at the base of the rot. Apply pressure as you pull the clawback towards you. Remove as much as you can without disturbing the healthy wood.

  • Don’t force the wood to remove it. Only get rid of the soft, rotting wood.

Use a router with a V-shaped bit to remove any remaining rotten wood. 

Hold the router, so the bit is 1⁄8 inch (3.2 mm) from the back edge of the wood. Use short back and forth strokes to grind away any rot you couldn’t reach with the hammer. Grind the wood until you reach healthy and solid wood. Harder wood will be more difficult for the router to cut through.

  • If rot is left inside the wood, there is a chance that it can start rotting again.

Sand off paint and surface rot. 

Many patching solutions will not stick to existing paint, so it needs to be removed. Either use a paint scraper or coarse sandpaper, around 60 grit, to remove any residue that is on the surface of the wood. Apply an even amount of pressure as you work in a circular motion.

  • Dirt, rust, or primer should also be removed from the wood’s surface before moving on.

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

Apply 4-6 coats of a wood restorer to the area. 

Use the provided brush to paint the restorer over the entire area. Let the restorer set for 2 minutes in between coats so it can soak into the wood. Let the restorer dry completely for 2 hours before working on it again.

  • Wear rubber gloves when working with the restorer to prevent it from coming into contact with your skin.

Making a Wood Patch

Make a smooth and straight cut in the wood using a Japanese hand saw. 

Place the teeth of the saw that are closest to the handle onto the line you want to cut. Apply pressure to the saw and pull it down at a 45-degree angle to make the cut. Repeat the cut until you can remove the wood by hand.

  • Mark the line you want to cut with a pencil, so you stay straight.

Trim a piece of cedar to the size of the hole you’re filling. 

Use a saw to cut the patch to the correct size. Make sure that the wood fits snugly in the rotted out area. If it’s too loose, it will not fit flush with the existing wood.

  • Cedar is commonly used as a patch since it is known for being rot-resistant.

Dampen the exposed wood with a wet rag. 

The glue you’ll be using activates with moisture. Use a damp cloth to rub the exposed wood where you’ll be placing the patch as well as the patch. It should feel slightly wet to the touch.

Apply polyurethane glue to the wood and place the patch. 

Squeeze the glue from the container directly onto the wood. Spread it, so it covers the entire exposed area. Press the patch against the wood tightly so the glue can begin to set.

  • Polyurethane glue foams and expands before it hardens so it can fill in any small gaps.
  • Do not touch the uncured glue with your bare hands or tools. It will be extremely difficult to remove.

Drill two screws into each side of the patch to hold it in place. 

Use screws long enough to reach the baseboards. Place one on each side of the patch to hold it in place while the glue sets.

Sand any excess glue off the patch after 6 hours.

It takes 6 hours for the polyurethane glue to completely dry and set. Use fine-grit sandpaper on the hardened glue to wear it down level with the wood.

Using Wood Filler for Patching

Pour a 3 in (7.6 cm) diameter circle of wood filler on a non-porous surface. 

Put the wood filler on a piece of plastic or glass, so it does not stick or get caught in the material. Make sure the circle is about 1⁄2 inch (13 mm) thick, so you have enough to mix initially.

Squeeze the tube of hardener with the cap still on. 

The hardening agent will separate in the tube, so firmly squeeze it with your fingers to ensure it is mixed together before you open it.

Put a 3 in (7.6 cm) strip of the hardener on the filler and mix. 

Use a putty knife to stir the filler and the hardener together for about 2 minutes. When it’s thoroughly mixed, it should have a light red colour.

  • The wood filler has a working time of 10 minutes, so only use small amounts at a time.
  • Keep the mixture spread thin so it will have a longer working time.

Apply the filler to the wood with a putty knife with firm pressure. 

Spread the filler 2 inches (5.1 cm) beyond the problem areas of the wood. Keep constant pressure on the putty knife, so the wood filler completely adheres. Spread the wood filler until you reach the desired thickness.

Let the filler dry for 30 minutes. 

The wood filler will completely set within a half-hour in temperatures cooler than 75 °F (24 °C). In warmer temperatures, it may take as little as 10 minutes for it to set.

Sanding and Painting Patched Wood

Smooth the patch with sandpaper. 

Make sure the edges of your patch are flush with the existing wood, so it has a uniform look. Start with coarse sandpaper, around 60 grit, and work down to a fine-grit paper, like 200 grit, for a completely smooth finish.

Use a matching stain if the original wood is stained. 

Paint a coat of the stain onto the wood and let it dry. Be careful not to overlap layers of existing stain since this may make the colour appear darker in that spot.

  • Patches of wood filler may stain a slightly different colour than the actual wood. Test the stain on a small part of the filler to see how it holds the stain.

Paint at least two layers of primer if the wood is painted. 

Use thin coats of grey or white primer so you can apply it evenly. Let it dry for 10 minutes before you start on another coat.

  • Use a spray primer for a more even coat and to avoid the look of brush strokes.

Apply a coat of paint after the primer has dried. 

Mix the paint with a stir stick, so it’s not separated when you use it. Paint thin coats with a paintbrush, so it evenly layers. Use long strokes that cover the entire length of the wood, so it has a smooth finish.

  • The paint should dry within 10 minutes unless it is very humid.

Repair, Don’t Replace, Rotten Wood.

Wood anywhere in your home is vulnerable to decay in the form of wet or dry rot. A rotten wooden door, floorboard, section of the trim, window sill, or column, maybe just the beginning of potentially serious problems. As a fungal infestation, rot can and will spread rapidly unless you take care of the trouble right away. Although replacing damaged wood is often a major hassle — not to mention the strain it puts on your wallet — cheer up! A complete replacement is often unnecessary for non-structural-support woodwork. Instead, build up the weakened area with the help of several easy-to-use products. Here’s how.

Eliminate the cause. 

Missing or loose roof tiles, plumbing leaks, poorly fitting doors and windows, inadequate stone pointing, and condensation all admit moisture into your home and allow rot to develop. Signs of dry rot (which, despite its name, actually requires a moisture content of at least 20 per cent) include discolouration, splitting, crumbling, or flaking of the wood, and an unpleasant mushroom-like odour. Wet rot occurs in areas with at least 50 per cent moisture content and usually shows itself as black fungal growth on wood, combined with a spongy, damp texture. After you fix the origin of the problem, if it is indoors, open as many windows as possible and ventilate the room using fans and dehumidifiers.

Remove the rot. 

Once you’ve identified rot anywhere in your home, the next step is getting rid of all the affected wood — essential before you begin to repair. Cut out only the rotted section of your wood (a 5-in-1 painter’s tool or a sharp putty knife is ideal for this task). Use a vacuum cleaner to tidy up any sawdust and other dirt.

Purchase a wood hardener and a filler – either polyester or epoxy – that are low odour and free of hazardous volatile organic compounds (VOCs). Wear rubber gloves when you work with these substances.

Use a small to medium brush to spread the hardener onto the surface, filling in cracks and completely covering the wood which surrounds the area where the rot was found. This will solidify and strengthen it to protect its structural integrity.

Next, mix a batch of wood filler. 

It should be the consistency of peanut butter when ready. Apply generously (any extra can be sanded off later) with a putty knife, shaping it to roughly the shape and size wanted. For large repairs, you may wish to construct a form to help mould the filler. Wood filler dries fast, especially on a warm Southern California summer day, so follow the lead of skilled San Diego handymen and work as quickly as possible. As the filler hardens, apply a 2nd, and if desired, a 3rd coat after all coats have completely dried, sand and clean off any dust left behind.

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

Prime the repaired section and then paint it to match the rest of the object. 

Use anti-fungal paint for the best results in guarding against future problems with dry or wet rot.

A word of warning. When you work on rotten timber, make sure you consider the likelihood that leads paint is present. Work health and safety precautions must be followed to stop the ingestion and transfer of old paint dust and chips.

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