Top 10 Best Wet Rot Treatment Products in the UK

In the UK’s damp climate, wet rot can creep into timber before you’ve even noticed. A leaky gutter, condensation, or driving rain is all it takes for moisture to linger, letting the fungus take hold. It starts quietly with soft patches, a musty smell or flaking paint, but can soon weaken beams, joists, and frames beyond repair.

The good news is, with the right treatment, you can stop it in its tracks. This guide reviews the best wet rot products for 2025, from deep-penetrating hardeners to all-in-one solutions, so you can protect your timber and avoid costly structural repairs.

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1. Everbuild Triple Action Wood Treatment – 5 Litre

Everbuild Triple Action in the larger 5-litre size is built for bigger jobs — from treating a whole shed to protecting multiple roof beams in one go. It gives long-lasting defence against wet rot, decay, fungi, and wood-boring insects.

The clear, solvent-free liquid penetrates deep into timber, works even on damp wood, and is suitable for both interior and exterior use.

Key Features

• Kills wood-boring insects and their larvae
• Protects against wet rot, dry rot, and fungi
• Works on damp or dry timber without losing performance
• Penetrates deep for lasting protection
• Ideal for large-scale indoor and outdoor wood treatment projects

Why We Recommend Everbuild Triple Action Wood Treatment – 5L

If you’re tackling wet rot across a larger area, this size makes sense. Same penetrating, fast-drying formula as the smaller bottles, just more of it. You can coat multiple surfaces in one session without worrying about running out, and it still applies easily with a brush or sprayer.

Check prices on Amazon: Everbuild Triple Action Wood Treatment – 5L

2. Soluguard Woodworm & Rot Treatment (5 Litre, Clear)

When timber starts showing early signs of damp or decay, Soluguard steps in as a reliable all-in-one solution. It attacks active woodworm and halts wet rot before it spreads, giving weakened wood a real chance to recover.

Solvent-free and low-odour, it works indoors or out without leaving strong fumes, and the 5-litre size treats up to 20m² — enough for loft joists, floorboards, or an entire shed. One thorough application and the wood stays protected for years.

Key Features

• Eliminates active woodworm and prevents future infestations
• Stops wet rot and dry rot from taking hold
• Solvent-free and low odour for safer indoor use
• HSE approved for both DIY and professional jobs
• Covers up to 20m² per 5-litre container

Why We Recommend Soluguard

Soluguard stands out because it targets wet rot as effectively as it handles woodworm. Its high-strength formula penetrates deep into timber, reinforcing weakened fibres from within. You don’t need separate products or multiple applications — a single coat locks in protection and stabilises the wood. Ideal for treating exposed beams, repairing floorboards, or protecting a shed from damp weather, it provides real peace of mind and long-lasting results.

Check prices on Amazon: Soluguard woodworm and wet treatment

3. Cuprinol 5 Star Complete Wood Treatment (WB) – 5 Litres, Clear

Some treatments claim to do it all — but this one genuinely does. Cuprinol’s 5 Star formula tackles timber problems on three fronts: it wipes out wet rot fungi, kills dry rot fungi, and destroys woodworm larvae before they’ve got a chance to do real damage. It’s water-based, so it soaks deep into the grain without leaving that heavy chemical smell, and once it’s in, the protection keeps working season after season.

Key Features

• Triple-action defence against wet rot, dry rot, and woodworm
• Gets deep into timber for thorough, lasting treatment
• Low-odour water-based mix for easier indoor application
• Backed by Cuprinol’s long-standing wood care expertise
• 5-litre tin ideal for whole-room or large project coverage

Why We Recommend Cuprinol 5 Star Complete Wood Treatment (WB) – 5 Litres

This isn’t just for the odd patch of damp wood in the shed. Cuprinol 5 Star is the treatment you bring in for a serious repair job you want to stop dead in its tracks. It’s professional-grade protection that’s still easy to apply with a brush or sprayer, and it’s trusted by homeowners who’d rather do one thorough job now than have to strip everything back again in a year.

Check latest price on Amazon: Cuprinol 5 Star Complete Wood Treatment (WB) – 5 Litres

4. Sika Sikagard Universal 5 Star Wood Treatment – Clear – 5 Litre

We’ve used quite a few wood treatments over the years, and the Sikagard Universal 5 Star consistently impressed us. When we applied it to older beams, garden fencing, and even slightly damp timber, it didn’t just sit on the surface — it soaked deep into the grain.

It tackles wet rot, dry rot, fungi, and wood-boring insects effectively, while still drying completely clear so the timber keeps its natural look. We’ve used it indoors and outdoors, and it performed every time.

Key Features

• Kills wood-boring insects and larvae
• Shields timber from wet rot, dry rot, and fungal decay
• Can be applied to damp wood without losing performance
• Solvent-based for deep penetration and quick drying
• Works on sheds, beams, floors, fencing, and furniture

Why We Recommend Sika Sikagard Universal 5 Star Wood Treatment

For any timber that needs more than a surface fix, this treatment is a solid choice. The solvent base drives the active ingredients right into the wood, reaching the stubborn areas where problems hide. Plus, because it dries clear, there are no unsightly patches or discolouration. It’s reliable, versatile, and easy to use on both indoor and outdoor timber.

Check prices on Amazon: Sika Sikagard Universal 5 Star Wood Treatment – 5L

5. Rustins Wood Hardener for Rotted Wood – 500ml

When timber starts to soften or decay, Rustins Wood Hardener is our go-to safety net. We’ve used it on old furniture, fence posts, and patchy decking boards, and it really does soak deep into the wood, locking loose fibres together.

Areas that would have crumbled if we’d tried sanding or painting were solid again within hours. Unlike surface coatings that just sit on top, this strengthens from the inside out — leaving the timber ready for filler, sanding, or a fresh coat of paint.

Key Features

• Deep-penetrating formula strengthens soft or rotted wood
• Works indoors and outdoors — from furniture to decking and fences
• Quick-drying (ready for filler in about 2 hours)
• Solvent-based for maximum absorption and reinforcement
• Dries clear, keeping the natural wood appearance

Why We Recommend Rustin Wood Harderner

We’ve repaired patchy fence panels and wobbly chair legs with this, and the difference is night and day. After treatment, the timber feels solid under pressure and is far less likely to crumble or flake. It’s the perfect fix when you want to rescue a piece of wood rather than replace it entirely. If you’re facing soft or damaged timber, this is the stabiliser we’d keep in the shed.

Check price on Amazon: Rustins Wood Hardener for Rotted Wood – 500ml

6. Ronseal Wet Rot Wood Hardener 250ml

When wet rot sets into timber, you don’t always have to strip the whole thing out. Ronseal’s Wet Rot Wood Hardener is a quick-acting fix designed for smaller jobs where speed matters.

It penetrates soft, damp-affected fibres and bonds them into a solid base ready for filler. Ideal for those “spot it, fix it” moments before the damage spreads.

Key Features

• Dries in just two hours for same-day repairs
• Soaks deep into softened timber to lock fibres together
• Forms a rock-hard base for wood filler application
• Suitable for both indoor and outdoor use
• Simple brush-on application, no special tools needed

Why We Recommend Ronseal Wet Rot Wood Hardener

This is the product you reach for when you’ve spotted early-stage rot and don’t want it getting any worse before the weekend’s over. Its fast-drying time is a standout — reviewers often mention tackling a garden trellis, bannister spindle, or shed panel in the morning and being ready to fill or repaint by the afternoon. While it’s not built for very deep, structural decay, it’s perfect for stopping rot in its tracks on decorative and light-duty woodwork.

Check prices on Amazon: Ronseal Wet Rot Wood Hardener 250ml

7. HOCHSTE® Wet Rot Wood Hardener (500ml, Clear)

HOCHSTE specialises in no-nonsense timber care, and this hardener shows it. It soaks into damp-softened wood, binds loose fibres, and shuts the door on moisture so wet rot can’t keep spreading.

What impresses us most is how cleanly it cures: it dries clear, then takes filler, sanding, and paint without crumbling—turning a write-off window sill or shed panel into a solid repair.

Key Features

• Deep, solvent-based penetration that locks weakened fibres into a hard mass
• Seals the grain to block moisture and halt wet-rot progression
• Brush on straight from the tin; no mixing, no special kit
• Dries clear; ready for filler/paint after cure (around 2 hours—check label)
• Interior/exterior use: ideal for window frames/sills, door bottoms, skirting, shed panels, fascia

Why We Recommend HOCHSTE

We rate this for targeted wet-rot fixes where you want to save original timber, not replace it: sash bottoms, threshold edges, fence tops, and other water-catching spots. It hardens from within, so repairs last instead of powdering under filler. Our recommendation comes from manufacturer specs and consistent buyer feedback; we prioritise products that reinforce the substrate first, then finish cleanly.

Check prices on Amazon: HOCHSTE® Wet Rot Wood Hardener 500ml

8. Lignum Fungicide & Insecticide Concentrate (1L)

Lignum has a reputation in the preservation trade for tough, multi-threat timber treatments, and this concentrate lives up to it. Designed for professional-grade use, it tackles three problems in one—woodworm, dry rot, and wet rot—making it a go-to for jobs where you can’t risk missing a hidden culprit. The low-odour, non-flammable formula works deep into timber and masonry, stopping insect activity and killing off rot-causing fungi at the source.

Key Features

• Dual action: kills wood-boring insects and eradicates dry/wet rot fungi
• Concentrated liquid for large-scale or high-risk timber treatments
• Low odour and non-flammable for safer indoor work
• Suitable for both timber and masonry in building preservation
• USDA specification met; trusted in professional property care

Why We Recommend Lignum

This isn’t a casual DIY spray—it’s the kind of treatment contractors use when they need one product to cover all bases in a serious infestation or outbreak. Perfect for older properties with mixed issues (woodworm plus early-stage wet rot), or preventative treatment during renovation. We rate it for its breadth of protection and reliability, especially when you want one job to last for decades, not just a season.

Check prices on Amazon: Lignum Fungicide & Insecticide Concentrate (1L)

9. Boracol B40/1 Boron Gel 400cc

Boracol B40/1 Boron Gel is a professional-grade timber preservative designed for deep, long-term protection. Combining Disodium octaborate tetrahydrate (DOT) with Benzalkonium chloride in a glycol base, it works as both an insecticide and fungicide—making it highly effective against woodworm, dry rot, and wet rot. The gel formula allows precise application through pre-drilled holes, ensuring full penetration into structural timbers where brush-on liquids can’t reach.

Key Features

• Kills wood-boring insects and protects against dry and wet rot
• Gel formula for injection into drilled holes in embedded timbers
• Suitable for joist ends, roof beams, floor timbers, and joinery
• Practically odourless and non-staining
• Approved under HSE COPR 1986 Regulations (HSE No. 6133)
• Designed for professional use with a standard 400cc mastic gun

Why We Recommend Boracol B40/1

When decay or infestation is hidden deep inside structural timbers, surface treatments aren’t enough. Boracol’s injectable gel ensures the active ingredients reach the heart of the timber, giving lasting protection where it’s most needed. We like it for joist ends, roof voids, and situations where standard liquid applications can’t fully penetrate. Its low odour and non-staining properties make it practical for sensitive projects and heritage work.

Check prices on Amazon: Boracol B40/1 Boron Gel 400cc – Boron Timber Treatment for Woodworm, Dry & Wet Rot (2)

10. Siramico Hardener for Rotted Wood – 500ml

Siramico Hardener is a polyurethane-based, deep-penetrating solution designed to restore and reinforce rotted or weakened wood. Its low-viscosity formula soaks into damaged fibres, solidifying the structure and protecting it from further deterioration. Suitable for both interior and exterior timber, it’s a go-to for repairs on window sills, door frames, beams, and other vulnerable woodwork.

Key Features

• Strengthens wet, rotted, or weakened wood fibres
• Deep penetration for long-lasting reinforcement
• Suitable for all timber types – indoor or outdoor use
• Water-resistant once cured to prevent future decay
• Easy to apply with a brush or roller – works even on damp wood
• 500ml tin covers up to 8m², ideal for multiple repairs

Why We Recommend Siramico Hardener – 500ml

For rotted wood that’s still salvageable, Siramico offers a cost-effective alternative to full replacement. Its ability to penetrate and cure within damp or compromised timber makes it especially useful in the UK climate, where moisture is often an ongoing issue. We rate it highly for preserving window sills, restoring structural timber, and extending the life of outdoor wood without the mess or odour of heavy-duty resin systems.

Check prices on Amazon: Siramico Hardener for Rotted Wood – 500ml

How Does a Wet Rot Treatment Product Work?

Wet rot treatment isn’t just a quick paint-over job — it’s a targeted chemical process that tackles the fungus at its source, strengthens the wood, and stops the problem from coming back. Here’s what’s happening behind the scenes:

1. Kills the Fungus Causing the Damage

Wet rot starts when timber stays damp long enough for fungus to take hold. That fungus feeds on the wood’s cellulose, breaking it down until it feels soft or crumbly. A quality treatment penetrates the fibres and kills the fungal growth, so it can’t spread any further.

2. Soaks Deep Into the Timber

The real damage often hides below the surface. Wet rot treatments are designed to seep right into the grain, reaching the invisible areas where decay is still active. For badly affected beams or joists, drilling and injecting the solution ensures full coverage.

3. Creates a Built-In Water Barrier

Once the treatment cures, many products leave a moisture-repellent layer inside the timber. This barrier slows down water absorption, cutting off the conditions that wet rot needs to return.

4. Strengthens Weak, Spongy Wood

Some formulas — especially those with hardeners — don’t just stop rot, they reinforce softened timber. That makes repairs possible without having to replace every affected section.

Bottom line: Wet rot treatment works by killing the source, locking out moisture, and restoring enough strength to give your timber a second life. Done properly, it can save you from major structural repairs later on.

How to Choose the Best Wet Rot Treatment Products?

Walking into a DIY store can feel overwhelming when you’re faced with a dozen “miracle” rot treatments. The key is knowing exactly what condition your timber is in—and matching it to the right type of product.

Assess the Condition of the Affected Timber

If the wood is only slightly soft, a rot killer followed by a wood hardener can often save it. But if you can push a finger straight through, no chemical will repair it—you’ll need to cut it out and replace it.

Choose Between Indoor and Outdoor Wet Rot Formulas

Some wet rot treatments are perfect indoors but release strong odours—not ideal in a living room or bedroom. Outdoor-grade formulas are designed to cope with rain, frost, and UV exposure. Always choose based on the timber’s location and exposure.

Use a Combined Wet Rot Killer and Wood Hardener for Mild Damage

For window sills, door frames, or beams that have softened but are still structurally sound, kill the fungus first, then apply a resin-based wood hardener. This restores strength so you can sand, prime, and paint as normal.

Check Penetration Depth for Effective Wet Rot Eradication

Solvent-based treatments often soak deeper into damp fibres—ideal if rot has started spreading inside the timber. Thicker, water-based formulas can be great for surface sealing but may not reach deep decay.

Factor in Drying and Curing Times Before Painting

Some products cure within hours; others take a full day or more before you can sand or coat the surface. If you’re working to a tight schedule, fast-curing products can make all the difference.

Look for Certified Fungicidal Protection Against Wet Rot

Always check the label for HSE approval or recognised fungicide certification. This ensures the product has been tested and proven to kill wet rot fungus effectively, especially in structural timber.

How to Apply Wet Rot Treatment Products Like a Pro

This is the stage that makes the difference between a quick fix and a lasting repair.

Prepping the wood: scraping, sanding, drying

We always start by scraping away loose, crumbly timber. Then sand until we hit solid wood. It’s crucial to get the area dry – a dehumidifier can help if needed.

Brush, injection, and soaking techniques

We use brushes for smaller areas. For thicker beams or deep damage, we drill and inject the wet rot treatment product. Soaking is mainly for pieces we can remove and submerge – not something that’s often possible in a fitted structure.

Safety tips and PPE essentials

Gloves, goggles, and a mask are non-negotiable. Even low-odour products aren’t something you want to inhale. And we always work in a ventilated space.

Can You Stop Wet Rot Without Replacing the Wood?

Sometimes, yes. If the damage is localised and not too severe, we can treat it and then consolidate the timber with a hardener.

If the wood is completely crumbly, there’s no saving it. At that point, the best approach is to cut it out, replace it, and treat the surrounding timber as a precaution.

How Long Do Wet Rot Treatment Products Last?

With proper application, treatments can last several years – five to ten isn’t unusual. But that lifespan depends on keeping the timber dry.

Skipping maintenance, ignoring leaks, or leaving poorly ventilated areas unchecked will shorten it. Good sealing, repainting on schedule, and quick repairs will make it last much longer.

Wet Rot Prevention Tips for UK Homes

• Keep gutters and downpipes clear.
  
• Make sure kitchens, bathrooms, and lofts are well ventilated.
  
• Check timber windows in spring and autumn.
  
• Fix leaks immediately, even if they seem small.
  
• Use quality exterior paint or sealant for weather protection.
  

Common Mistakes to Avoid With Wet Rot Treatments

• Treating damp timber without drying it first.
  
• Using the wrong product for exterior work.
  
• Applying treatment without sorting out the source of moisture.
  

FAQs on Wet Rot Treatment Products