Complete Dry Rot & Wet Rot Service Cardiff and the Vale of Glamorgan

PCA Qualified Surveyors — Dry Rot & Wet Rot services With Our Guarantee of Satisfaction.

Dry Rot, Wet Rot & Timber Decay — Survey, Treatment & Full Reinstatement

Timber decay — whether dry rot or wet rot — is rarely limited to what you can see on the surface. Both are caused by wood-destroying fungi that break down the structural fibres of timber, and both require a thorough survey to establish the full extent of the problem before any treatment begins.

Dry rot in particular has a notorious ability to spread far beyond the timber itself, sending fungal strands through brickwork, mortar joints, and masonry in search of new food sources.

That’s why an accurate diagnosis is absolutely essential. Treat too little and the decay continues. Treat without understanding the underlying moisture source, and it will almost certainly come back.

Dry Rot vs Wet Rot — What You Need to Know

Dry Rot

Dry rot is the most serious and destructive form of timber decay found in UK buildings. Despite its name, dry rot does require moisture to become established — it needs a timber moisture content of around 20% or above to germinate — but once it takes hold, it has a remarkable ability to transport water through its own mycelium network, allowing it to spread into areas that appear perfectly dry.

The causative organism, Serpula lacrymans, is uniquely damaging because its root-like structures known as rhizomorphs can penetrate through plaster, mortar, and masonry to reach new timber far beyond the original outbreak. An infection in one room or floor level can spread through wall cavities and structural timbers in adjacent areas, which is why a thorough survey is so important before any treatment begins.

How to identify dry rot:

Cuboidal cracking — the timber breaks into distinctive brick-like sections, cracking both along and across the grain. This is the most recognisable sign of dry rot.
White or grey fluffy mycelium a cotton wool-like growth spreading across the surface of timber or adjacent masonry, sometimes covering large areas in enclosed spaces
Rust-red or orange spore dust often deposited in patches around the fruiting body and can be found on surrounding surfaces
Fruiting bodies fleshy, pancake-shaped growths with an orange centre and white margin, sometimes appearing on walls, floors, or skirting boards at a distance from the timber source
Grey or lilac-tinged rhizomorphs cord-like fungal strands crossing masonry, brickwork, or plaster
Timber that feels light, crumbly, and has lost all structural strength
A distinctive musty, mushroom-like smell particularly noticeable in enclosed or poorly ventilated spaces

Where dry rot commonly occurs in Cardiff and Vale properties:

Suspended timber ground floors in Victorian and Edwardian terraces — particularly where airbricks have been blocked, covered by raised garden levels, or never cleaned out
Roof timbers and loft spaces following roof covering failures, missing felt, or the deterioration of lead flashings around chimney stacks and valleys
Behind fixed panelling, built-in wardrobes, or boxing that has concealed a slow leak or rising damp for years
Floor joists and wall plates at ground level, particularly where they sit on damp masonry without adequate DPC protection
Period properties across Pontcanna, Llandaff, Canton, and the Vale — where large original timbers have been in contact with moisture ingress for extended periods

How we treat dry rot:

Full survey and mapping: We establish the complete extent of the outbreak, including probing adjacent masonry and timbers beyond the visible signs of infection. Dry rot is rarely as contained as it first appears.
Moisture source identification and elimination: Dry rot cannot survive without moisture. We find and fix the source — whether that’s a plumbing leak, failed roof covering, blocked drainage, or a compromised damp proof course — before treating the fungus.
Removal of all affected timber: Decayed timber is cut back to a minimum of 300–500mm beyond the last visible signs of infection. This margin is essential — leaving even small quantities of infected timber provides a base for regrowth.
Masonry sterilisation: All affected brickwork, mortar, and plaster is treated with a fungicidal solution to destroy residual mycelium and rhizomorphs that have penetrated the structure. In severe cases, heat treatment is applied to the masonry surface prior to chemical sterilisation.
Fungicidal timber treatment: All retained and new timber within the outbreak zone is treated with a boron-based or approved organic solvent preservative system to prevent future fungal attack.
Structural reinstatement: Replacement timbers are pre-treated with preservative before installation. Where joist ends or wall plates are renewed, physical DPC trays are used to isolate new timber from masonry and prevent moisture contact.

Wet Rot

Wet rot is considerably more common than dry rot and, while it is less aggressive in terms of its ability to spread through a building, it can still cause very serious structural damage if the underlying moisture source is left unaddressed. Unlike dry rot, wet rot remains localised to the area of elevated moisture — its mycelium cannot spread through masonry — but it will continue to break down timber for as long as damp conditions persist.

Several species of fungi cause wet rot. The most frequently encountered in UK properties are Coniophora puteana (cellar fungus) and Fibroporia vaillantii. All require a timber moisture content in excess of approximately 50% to thrive, and all cause a similar pattern of decay — softening and darkening the wood, breaking down its structural fibres, and eventually causing it to collapse under load.

How to identify wet rot:

Timber that feels soft or spongy to the touch — particularly noticeable around window sills, door frames, and external joinery
Darkening or discolouration of timber — affected wood is typically darker than the surrounding healthy material
Cracking along the grain — less pronounced than dry rot’s cuboidal pattern, and following rather than cutting across the timber grain
Paint or surface coating that feels hollow, bubbles, or lifts — a strong indicator that the timber beneath has lost its rigidity
Thin, localised fungal growth visible in advanced cases — fine white or dark strands on the surface of heavily affected timber
A musty, earthy smell — often strongest in poorly ventilated spaces such as under floors, in cellars, or in flat roof voids

Where wet rot commonly occurs:

External window frames and door frames — particularly those with failed or neglected paint systems that have allowed moisture to penetrate the end grain
Flat roof timbers where ponding water or a failed roofing membrane has kept the structure consistently wet
Ground-floor joists and skirting boards in properties with rising damp, poor subfloor drainage, or blocked airbricks
Areas adjacent to leaking or overflowing gutters, downpipes, and soil stacks — particularly common in Cardiff’s older terraced housing
Roof timbers at valleys, hips, or chimney flashings where water ingress has been occurring over a prolonged period

How we treat wet rot:

Moisture source removal: The first and most important step. Wet rot cannot survive in dry timber — eliminate the moisture and the fungus cannot persist.
Removal or consolidation of decayed timber: Heavily deteriorated timber is cut back and replaced. Where decay is localised — such as a small section of a window sill — a resin repair system may be used to consolidate remaining sound timber and fill the affected area without full timber replacement.
Fungicidal timber treatment: Retained and adjacent timber is treated with an appropriate fungicidal preservative to protect against future decay and neutralise any residual fungal material.

Reinstatement: All replacement timber is pre-treated before installation. We ensure the conditions that led to the original decay — whether a failed paint system, absent DPC, or inadequate drainage detail — are corrected as part of the reinstatement work.

Why Choose Damp Armour Cardiff for Dry Rot & Wet Rot Treatment

Trust and Recommendations.

The bulk of our work comes from recommendations from satisfied customers.

Guaranteed Service.

We care about or reputation, which is why we offer such a good guarantee

There’s no shortage of contractors offering remedial timber treatments in Cardiff but not all of them are qualified, and not all of them will give you an honest assessment. Here’s why our customers keep recommending us:

Above all else, get a survey before you do anything, know what you are dealing with and plan for it.

Let’s discuss how we can improve your conditions and stay within budget.

We will always do our best to do what’s best for you.

Survey First — Always Before Any Treatment

Timber decay is notoriously easy to underestimate. Our PCA qualified surveyors probe adjacent timbers, check hidden voids, and trace the spread of any fungal growth well beyond its visible boundaries before making any treatment recommendation. You’ll receive a clear written report of findings and a fully itemised quotation — before a single piece of timber is touched.

Complete Service — Survey to Reinstatement

We handle the full scope of work from start to finish — cutting out decayed timber, sterilising affected masonry, installing pre-treated replacement timbers, and re-plastering where required. One contractor, one point of contact, and a job that’s done properly rather than handed off piecemeal.

Approved Contractors — Sovereign Chemicals & Wykamol

We’re approved contractors for two of the most respected names in the damp proofing and timber preservation industry. Sovereign Chemicals and Wykamol produce industry-leading treatment products, and their approved contractor schemes ensure that work carried out by our team meets the required standard for their product guarantees. That means the guarantee on your treatment is backed by the manufacturer — not just by us.

Transparent, Itemised Pricing

You’ll receive a clear, written quotation before any work begins. No hidden costs, no unexpected additions to the bill. We break down exactly what work is involved and what each element costs — so you can make an informed decision and have complete confidence in what you’re agreeing to.

Local Knowledge of Cardiff Properties

We work across Cardiff and the Vale of Glamorgan day in, day out. We know how wet and dry rot presents in the Victorian terraces of Roath and Canton. We understand the dry rot challenges in solid-walled properties in Llandaff and Pontcanna. That local experience matters it means we diagnose faster and treat more accurately than a generalist contractor who doesn’t know the area.

Plastering Included

One thing that sets us apart is that we offer a complete service — including plastering. Many dry and wet rot contractors treat the structural issue and then leave you to find and coordinate a separate plasterer. We handle the full job from survey through to re-plaster, leaving your property clean, tidy, and ready to redecorate.

Nebosh Certified — Health & Safety Compliant

We hold a Nebosh certificate, demonstrating our commitment to maintaining the highest health and safety standards on every job. You can have confidence that our team operates safely, responsibly, and in compliance with current regulations.

We’ve treated dry rot and wet rot in properties right across Cardiff and the Vale of Glamorgan — from Victorian terraces in Roath and Canton with failing subfloor ventilation, to period farmhouses in the Vale where persistent moisture ingress has been breaking down structural timbers for years. Every job follows the same approach: identify the moisture source, establish the full extent of any decay, eliminate both, and reinstate to a standard that lasts. We are approved contractors for Sovereign Chemicals and Wykamol, and all timber treatment work is carried out using industry-approved fungicidal and preservative products — giving you the confidence of a manufacturer-backed guarantee on the treatment applied.

PCA qualified surveyors — fully accredited timber decay and damp specialists
Guaranteed workmanship using Sovereign Chemicals and Wykamol approved treatment systems

Let’s discuss how we can improve your situation and stay within budget.

Timber decay doesn’t wait, and neither should you. The longer rot goes untreated, the further it spreads and the more structural damage it causes — which means a bigger job and a significantly higher bill.

Give us a call today and speak with one of our PCA qualified timber specialists. We’ll have a straightforward conversation about what you’re seeing, give you an honest assessment, and arrange a survey at a time that works for you.