How to Detect, Treat & Replace Rotten Floorboards

If there are signs of rot in the floorboards of your home, it’s important to act fast.

Not only can rotten floorboards pose safety hazards, but the presence of the decay can damage your home’s structural integrity. In this guide, we’ll explore how to identify both wet rot and dry rot in floorboards, the treatment options which we offer, and how we can replace the floorboards, if required.

Read on for expert tips from our highly experienced timber preservation specialists.

How to tell if floorboards are rotten

Detecting rotting floorboards in time to treat them can save you money and stress, as replacing floorboards is more costly. Here’s how to spot a rotten wood floor:

  • A spot on a wooden floor that feels soft or is sagging underfoot can be a sign that a floorboard is rotting and losing its structural integrity
  • Discolouration or lighter/darker spots on your wooden floor can be caused by water affecting floorboards and leading to timber decay
  • If you smell a musty smell coming from a floorboard (caused by the wood decomposing), this can be a sign that the floorboards are rotten

Is my rotting floor caused by wet or dry rot?

If you suspect floorboards are affected by rotting wood, it’s important to know the difference between dry and wet rot. These types of decay share some similarities and it can be tricky to tell the difference.

Here are a few key things to look for when identifying dry and wet rot in floorboards.

Moisture content – wet rot tends to happen in areas that are consistently damp, such as a wooden floor that is exposed to water ingress, poor ventilation, or plumbing problems. Dry rot only needs a 20% moisture content (compared to wet rot’s 50%) to take hold in timber.

Fungal growth – wet rot and dry rot are both caused by fungus, but they look different. Wet rot fungus is more localised and is less extensive, while dry rot often shows as white strands, white or grey cloud-like structures, and mushroom-like fruiting bodies with red spore dust.

Wood appearance – as wet rot tends to affect only damp wood, the wood may appear dark and spongy, and it may show some signs of cracking. Dry rot can cause distinct ‘cubical’ fractures, significant wood shrinkage, and will cause wood to appear crumbly and brittle.

Spread pattern – wet rot often remains local to areas of damp, such as floorboards near a leaky pipe. Dry rot can spread through masonry and building materials, including brickwork and plaster – its spores are more aggressive which makes it easier for dry rot to spread to multiple areas, faster.

You can find out more about wet rot and dry rot on our dedicated treatment pages.

What do rotten floorboards look like?

Here are some images of rotten floorboards to help you decide whether yours need help.

Dry Rot on Wooden Floorboards
Wet Rot causing a floor to collapse
Wet rot on Wooden Floorboards

Of course, it is worth calling one of our specialists in timber preservation to check. As both types of rotting wood can look similar, we’d recommend contacting a qualified professional. Our team can carry out a detailed inspection of your property and an accurate diagnosis.

Treating rotten wooden floorboards

If you suspect that you have found a rotting wood floor, it’s essential to sort the issue out as soon as you can. Here are some options for treating rotten floorboards, before they’re beyond saving:

  • Dry out the area affected by water intrusion or rot. Identify where the water is coming from, for example a leak or other source of water, and remove the source of moisture by fixing it. You should also let the floorboard dry out completely before treatment.
  • Remove any rotten wood using a chisel or a pry bar. Carefully remove the wood that is affected, not forgetting any areas surrounding the wood that show signs of decay.
  • When you’ve dried the area and removed any wood showing signs of decay, it’s time to get a wood preservative applied. This can help to prevent the floorboard from decaying further, and contain chemicals that kill fungus and prevent its growth.
  • Once the preservative is applied, use a wood filler to fill the void left behind. When the filler is dry, sand the area flat and use paint or varnish to seal and protect it.

How to replace rotten floorboards

Sometimes, wood rot can cause damage to floorboards that can’t be repaired. When this happens, you will need to replace the floorboards (or get a professional to do it for you).
Here is the basic process of replacing a rotten floorboard if it’s beyond repair.

  • Use a circular saw or handsaw to carefully cut out the rotten floorboard along its edges. To ensure a precise fit, measure and mark the replacement board.
  • Install the new floorboard by cutting a replacement to the right size. You can install the floorboard in the space by securing it with screws or nails to keep it stable.
  • To make it level with the old floorboards around it, sand the edges of the new replacement floorboard. You can also paint or stain it to match the rest of the floor.

How much does it cost to treat and replace a rotting wood floor?

The cost of replacing rotten floorboards depends on a variety of factors, including the extent of damage, whether it’s dry or wet rot, the size of the affected area, and the type of wood.

For treating a rotting floorboard, the estimated cost is typically around £1,000-£2,000 plus VAT. This price includes the identification and assessment of the damage, removal of the affected floorboard(s), treatment to prevent further rot, and any necessary repairs. It’s important to address the issue promptly to avoid further damage and ensure the longevity of your flooring.

In cases where the damage is extensive or affects a larger area, replacing the entire floor might be necessary. The estimated cost for replacing a whole floor can range from £2,000 to £4,000. This estimate includes the removal of the old flooring, preparation of the subfloor, installation of new floorboards, and any additional finishing work required.

The last word on treating or replacing rotten floorboards

If you want to keep your floorboards safe and stable, it’s essential to look out for signs of wet and dry rot. By addressing issues quickly and following the recommended treatment and replacement steps, you have more chance of ensuring a durable floor for years to come.

While we can provide general information and guidance, we strongly advise seeking professional assistance for proper assessment and treatment. Qualified experts have the knowledge, experience, and specialised tools to handle rot-related problems effectively.

By contacting professionals, you can ensure the optimal care and preservation of your floorboards, promoting their long-term durability and minimizing the risk of further damage. Our team is readily available to provide professional assistance and advice, so please don’t hesitate to reach out to us for expert support.

A rotting floor can also be a sign of other issues within your home, such as condensation and mould and rising damp. If in doubt, why not book a free timber survey with us?

We have more than 40 years of experience treating rotting floorboards all around the UK.

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