Timber and Woodworm Survey: What It Checks and What It Costs

Timber is a fundamental building material in UK properties — from roof rafters and floor joists to window frames and staircases. Over time, timber can be attacked by wood-boring insects (woodworm) and fungal decay (wet rot and dry rot), both of which are commonly flagged in buyer surveys. Understanding what a timber survey involves and what the findings mean helps you prepare your property for sale and manage buyer expectations.

For a broader overview of the survey process and what buyers look for, see our seller's guide to property surveys. This guide covers everything sellers need to know about timber and woodworm surveys, from what the surveyor inspects to treatment options, costs, and the impact on your sale.

What a timber survey inspects

A timber survey is a systematic inspection of all accessible timber elements in the property. The surveyor will examine the following areas.

Roof timbers

The loft space is one of the most important areas for a timber survey. The surveyor inspects rafters, purlins, ridge boards, ceiling joists, and any structural beams. Roof timbers are particularly vulnerable because any roof leak introduces moisture that can sustain both fungal decay and beetle infestation. The surveyor checks for bore holes, fungal growth, staining, softening, and any signs of structural compromise.

Floor joists and floorboards

Where accessible (through lifted floorboards or from a sub-floor void), the surveyor inspects floor joists for beetle damage and fungal decay. Ground-floor joists in suspended timber floors are especially vulnerable because of their proximity to ground moisture. Adequate sub-floor ventilation — provided by airbricks in the external walls — is essential to keep timber moisture levels below the threshold for fungal attack.

Skirting boards and door frames

These non-structural timbers are often the first to show signs of woodworm, particularly at ground-floor level where moisture levels are highest. While damage to skirting boards and door frames is less serious than damage to structural timber, it can indicate that conditions are favourable for infestation and that structural timber nearby may also be affected.

Window frames

Timber window frames are exposed to weather and are prone to both wet rot (where paint seals have failed and moisture has penetrated) and woodworm. The surveyor checks the condition of the timber, particularly at the bottom rail and sill where water tends to collect.

Stairs and structural beams

Staircase timbers, structural beams, and lintels are checked for integrity. In older properties with exposed timber beams, the surveyor will check for death watch beetle — a species that specifically attacks hardwood and is particularly associated with oak-framed buildings.

Types of woodworm in UK properties

Several species of wood-boring beetle are found in UK properties. Identification matters because the species determines the risk level and treatment approach.

Common Furniture Beetle (Anobium punctatum)

By far the most common species, responsible for the vast majority of woodworm found in UK homes. It attacks softwood (and some hardwoods) and produces small, round bore holes approximately 1 to 2mm in diameter. The lifecycle takes two to five years: the adult beetle lays eggs on or in timber; the larvae bore through the wood, creating tunnels and producing frass (fine, gritty sawdust); and the adult beetles emerge through the surface, creating the characteristic exit holes.

Common Furniture Beetle is found throughout UK properties — in roof timbers, floor joists, floorboards, skirting boards, and furniture. While it can weaken timber over multiple generations of infestation, it is rarely catastrophic and is treatable.

Death Watch Beetle (Xestobium rufovillosum)

This species primarily attacks hardwood timber, particularly oak, and is mainly found in older period properties (pre-Victorian) and churches. Its bore holes are larger — approximately 3mm in diameter — and the frass is coarser, containing visible pellets. Death Watch Beetle requires higher moisture levels than Common Furniture Beetle and is often associated with damp conditions. It is a more serious pest because it tends to attack large structural timbers.

House Longhorn Beetle (Hylotrupes bajulus)

The most destructive species, but fortunately the rarest in the UK. It mainly affects softwood roof timbers and has historically been concentrated in parts of Surrey, Hampshire, and Berkshire, though it can occur elsewhere. Its bore holes are oval, approximately 6 to 10mm in diameter, and the larvae can cause severe structural damage because they are much larger than those of other species. Building Regulations in certain areas require pre-treatment of roof timbers as a precaution.

Comparison table

Active vs historic infestation: the key distinction

For sellers, the most important question about woodworm is whether it is active (ongoing) or historic (ceased). This distinction directly affects the sale.

Signs of active infestation

• Fresh bore holes with clean, sharp edges and light-coloured wood visible inside the hole.
• Fresh frass (wood dust) below the bore holes — it should feel gritty when rubbed between finger and thumb.
• Live beetles or larvae found in or near the timber (the flight season for Common Furniture Beetle is typically May to September).
• Bore holes increasing in number over time (compare photographs taken months apart).

Signs of historic infestation

• Bore holes with darker, worn, or softened edges.
• No fresh frass visible below the holes.
• Bore holes partially obscured by paint, dust, or dirt.
• No increase in the number of holes over time.

Historic woodworm is extremely common in UK properties and, provided the timber remains structurally sound, is rarely a cause for concern. It does not usually require treatment and should not significantly affect your sale. Woodworm is one of the most common survey issues found in UK homes.

Fungal decay: wet rot and dry rot

A timber survey also checks for fungal decay, which is caused by sustained high moisture levels in timber. There are two main types.

Wet rot

Wet rot occurs when timber maintains a moisture content above 28% for a prolonged period. It is caused by various fungal species and is confined to the area of wetness. Common locations include window frames (where paint has failed and water has penetrated), door thresholds, ground-floor skirting boards in damp areas, and any timber in contact with or close to a source of moisture (such as a leaking pipe or gutter).

Treatment for wet rot involves eliminating the moisture source, removing and replacing badly affected timber, and treating remaining timber with a fungicidal preservative. The key is addressing the cause of the dampness — without sustained moisture, wet rot cannot progress.

Dry rot

Dry rot (Serpula lacrymans) is the most serious form of timber decay in UK buildings. Despite its name, it requires some moisture to germinate (timber moisture content above 20%), but once established, it can spread extensively through masonry, across dry timber, and even through plaster and brickwork using its root-like mycelium strands (hyphae).

Signs of dry rot include a distinctive mushroom-like smell, white or grey cotton-wool-like mycelium on timber and masonry, rusty red spore dust, timber that cracks into cuboidal shapes and crumbles when touched, and the fruiting body — a flat, pancake-like growth with a rust-red centre and white margin.

Dry rot treatment is invasive and expensive. It involves removing all affected timber (plus a safety margin of at least one metre beyond the visible decay), stripping plaster from affected walls, applying fungicidal treatment to masonry, replacing timber with pre-treated alternatives, and eliminating the moisture source. Costs for dry rot treatment typically range from £2,000 to £10,000 or more, depending on the extent of the outbreak.

Treatment options and costs

All treatment should be carried out by a PCA-accredited contractor and come with a transferable guarantee. This guarantee is a valuable document for your sale — it reassures buyers and mortgage lenders that the work was done to a recognised standard and that recourse is available if the problem recurs. If the buyer's lender imposes conditions, they may apply a mortgage retention until treatment is completed.

How timber findings affect your sale

Historic woodworm (no active infestation)

This is the most common finding and has the least impact on a sale. Buyer surveys will note the bore holes, but if the timber is structurally sound and there is no evidence of active infestation, most buyers and lenders will accept the situation without requiring treatment or price adjustments.

Active woodworm

Active woodworm is more concerning but treatable. Treatment costs are relatively modest (£500 to £1,500 for spray treatment), and the transferable guarantee adds value. Treating before selling is usually the best strategy, as it removes the issue from negotiations entirely. For help deciding whether to fix issues or accept a lower price, see our guide on when to fix vs reduce price after survey. If you prefer not to treat, expect the buyer to negotiate a price reduction at least equal to the treatment cost — see our data on average price reductions after survey. For further guidance on that decision, see our guide on selling a house with woodworm.

Wet rot

Wet rot treatment is primarily about fixing the moisture source and replacing affected timber. If the repairs are straightforward (such as replacing a rotted window sill and repainting), completing them before marketing is advisable. For more extensive wet rot, provide quotes and discuss with your buyer.

Dry rot

Dry rot has the most significant impact on a sale. The word "dry rot" in a survey report can alarm buyers, and mortgage lenders may impose strict conditions. If dry rot is identified, professional treatment with a PCA-guaranteed contractor is essential — either before marketing or as a condition of the sale. Having the treatment completed and guaranteed before marketing is by far the strongest position for sellers.

For information on how damp conditions contribute to timber problems, see our guide to damp surveys. For related costs, see our guide to selling a house with damp.

Choosing a timber surveyor

As with damp surveys, independence matters. Timber treatment companies that offer free surveys have a commercial incentive to recommend treatment. An independent surveyor — particularly one accredited by the Property Care Association (PCA) — provides an objective assessment.

Many damp and timber specialists offer combined surveys, which is logical since the two issues are closely related. Sustained damp creates the conditions for both fungal decay and beetle infestation. A combined damp and timber survey typically costs £250 to £500 and provides a comprehensive picture of your property's condition.

The survey report should clearly state whether any infestation is active or historic, identify the species of beetle (if possible), assess the structural adequacy of affected timber, and provide clear recommendations for any remedial work. A well-written, objective report from an accredited surveyor is a powerful document for managing buyer negotiations and supporting mortgage applications.

Frequently asked questions