how to treat wet rot

How to Treat Wet Rot and Dry Rot (2021 UK Treatment Guide)

Buying an old property that has fallen into disrepair can be a great way to snag a bargain in today’s hot property market. However, neglected properties often suffer from wet or dry rot which can make properties uninhabitable. This guide will teach you how to treat wet rot and dry rot.

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Tools & Materials


  • Chisel
  • Drill
  • Paintbrush/Sprayer/Scraper/Sealant gun


  • Boron or Permethrin woodworm treatment
  • Plastic wrap
  • Wood filler
  • Spare timber
  • Dry rot paint (optional)

How to Treat Wet Rot and Dry Rot – Step-by-Step Instructions

1. Identify Wet Rot and Dry Rot

Wet Rot

damage caused by wet rot
  • Wet rot has three varieties. Coniophora puteana has dark grey/brown/black stands and stays flexible when dry. Fibroporia Vaillantii has thick white strands, while Asterostroma has thin white strands.
  • Wet rot Mycelium sheets are always bright white.
  • Wet rot produces tiny mushrooms that are beige and is caused by wood-boring weevils, identifiable by the fine sawdust they leave behind.
  • Wet rot has an earthy smell and will cause the paint to flake off. The wood will be soft to touch.
  • Small cracked squares across the wood are the final sign of wet rot.

Dry Rot

Identify rot
  • Dry rot has white or grey root-like strands. These dry out and become brittle.
  • Sometimes rot forms sheets called Mycelium. Dry rot is either off-white, pale yellow or lilac.
  • Dry rot produces flat spores that are red in the centre with an off white surround. Dry rot spreads using these red fungal spores.
  • The final sign of rot is cracking across the wood. Large misshapen cracks indicate dry rot.

Pro Tip: Masonry can also be affected by dry rot. Check out this advice page from Permaguard for more information.

2. Choose a Treatment Method

The remedies for dry and wet rot differ slightly. Wet rot has an extra set of steps where the treatment needs to be applied to the surviving wood. For more information on treatment options and costs, please check out ‘How Much Does Woodworm Treatment Cost?‘.

Boron Based Treatment

Boron treatment is easy to apply, safe for animals, and water-based which makes it odourless. It comes in a solution for large patches and a gel for heavily infested areas or places where extra water would be a hindrance. Using a large paintbrush, simply coat the area with the solution.

Boron Epoxy paste and rods should be used in places where the timber will be permanently wet. The paste is squeezed into the gap left by rot and rods are inserted the length of the timber.

The treatment kills the spores and hardens the wood, preventing the rot from returning.

Permethrin Based Treatment

When permethrin is applied to the surface with a brush or a spray gun, it seeps about 5 mm deep, effectively targeting larvae and adult beetles. Permethrin surface treatment works well when dealing with the Common Furniture Beetle, but it’s less effective for Deathwatch beetles as they burrow deeper into the timber.

The best way to kill the Deathwatch infestations with permethrin is to inject a gel solution into the timber. Although it’s possible to do this by injecting the gel into existing exit holes, drilling new holes often yield better results.

The downside of permethrin treatment is that it’s highly toxic. If you choose this method, you should wear a mask, eye goggles and gloves during the application process and vacate the area for a couple of hours afterwards. Due to its toxicity, the use of permethrin should be avoided if you have kids or pets.

At PWS, we highly recommend SoluGuard Woodworm Treatment (see below)

SAFEGUARD Soluguard Woodworm Treatment - Ready For Use High Strength Woodworm Killer Spray (5 Litre, Clear)
  • High strength woodworm treatment - 0.2% Permethrin
  • Targets all woodworm lifecycle stages (eggs, larvae, and adult beetles)
  • Extremely stable & solvent free (no solvent smell)
  • Apply by brush or spray
  • Treats 15-20m²

3. Remove Rot

hole in ceiling caused by rot

With a chisel, scrape out rotten sections of timber. If the wood is rotten through, cut out section with a hand saw. Drill evenly spaced holes in remaining timber to help the wood absorb the treatment.

If you have dry rot, skip ahead to step 7.

For wet rot, continue from step 4.

4. Prepare Remaining Wood

Drill evenly spaced holes in remaining timber to help the wood absorb the treatment.

5. Apply Treatment

Mix up solution according to manufacturer’s instructions and paint on with a large clean brush. Epoxy pastes will need to be spread on with a PALETTE KNIFE, or inserted using a sealant gun.

6. Let Dry

Leave to dry, covering with plastic wrap if the area will be exposed to moisture during the drying time. This is usually two hours, but check the instructions on the packet.

7. Replace Wood

If necessary replace rotted wood by inserting cut timber patches or using wood filler.

For wet rot, you are now finished. There is one more step for dry rot.

8. Prevention (dry rot only)

window rot

Apply dry rot paint around affected areas to prevent spreading.

As long as dry and wet rot is treated, it shouldn’t pose a problem. It’s a nasty thing to deal with, but once the rot is removed and the wood treated as per the above instructions, it shouldn’t return.

Don’t fancy doing this job yourself?

Then find top-rated wet rot and dry rot specialists in your area by clicking the button below:

How to Treat Wet Rot and Dry Rot – Final Thoughts

If you still need help, check out the video below, which gives you a close up view of wet rot on a windowpane and how to treat it.

If you have found this guide helpful, please share it with friends & family on social media.