Woodworm Treatment Oxford | Wet Rot and Dry Rot Repairs

Which wood-boring beetles need treatment in an Oxford house?

Usually the common furniture beetle, and only if it is still active. The Property Care Association calls it "the most common of the wood destroying insects found in buildings in the UK". Its exit holes are round and roughly 1.5 mm wide, its frass gritty and lemon-shaped, and it does most harm to timber that has been in service for at least 10 years. Larvae feed inside the wood for 3 to 5 years.

Deathwatch beetle prefers decayed hardwoods and leaves exit holes about 3 mm across, with bun-shaped pellets in its frass. Dr Brian Ridout notes that it normally attacks oak and that "Partially decayed wall plates and bearings in damp walls make an ideal home for the beetles". Weevils attack only damp, partly decayed timber.

House longhorn beetle is the one with its own building rule, but the requirement to treat roof timbers against it applies only in the districts listed in Approved Document A, Table 1, in parts of Surrey, Berkshire and Hampshire. Oxfordshire is not among them.

How can you tell whether woodworm is still active or long dead?

Look for fresh signs: clean, sharp-edged holes with bore dust trickling out, and new frass below. The PCA says all timber should be investigated for current activity "to justify any form of treatment", and that some timbers show historic activity where the insect may be extinct. Ridout's conservation advice is to cover holes with paper or fill them with polish, then check for new emergence.

Timing matters. Adult furniture beetles appear from March to September, often on window ledges, and the PCA says insecticides work best from early spring to late summer, when adults emerge. A midwinter survey may need a follow-up check in that season.

When activity is proved, the PCA guidance on treating woodworm starts with establishing that the infestation "is active and requires action", then calls for targeted, professionally applied wood preservatives for furniture beetle.

Does old woodworm in a Georgian or Victorian Oxford house need spraying?

Often it does not. Dr Brian Ridout calls precautionary spraying of roofs in Georgian and Victorian buildings "generally an unjustifiable use of pesticides", says surface sprays are generally ineffective and can kill natural predators such as spiders, and explains that old-growth timber had little sapwood, so "The majority of the timber in our Georgian and Victorian buildings is therefore resistant to furniture beetle attack". Twentieth-century plantation timber is more vulnerable.

That matters in Oxford, where a BRE study for the City Council estimated that 50% of the housing stock was built before 1944, and where there are around 1,500 listed buildings. For listed homes, the Council says consent covers any work, internal or external, that will affect the special character, including repairs that replace important fabric.

Cutting out historic joists may therefore need consent, so Oxford Damp Specialists starts with a targeted repair that keeps sound timber. Our guide to damp in old and listed buildings covers consent.

What is the difference between wet rot and dry rot in house timbers?

Both are wood-rotting fungi that need wet timber; what sets dry rot apart is that its strands can cross brick and stone and colonise timber beyond the wet spot. The PCA regards sorting rot into wet and dry as misleading: wet rots need no more moisture than dry rot and usually stay in regularly wet areas or in wood built into masonry, while dry rot can move fairly fast when conditions suit it and grow over masonry to colonise vulnerable wood.

Wet rot is not harmless. Weakened timber "should be removed and replaced", according to the PCA's wet rot treatment advice, though large or important timbers can be spliced or resin-bonded if they are kept dry.

BRE scientists point out that although dry rot strands pass over and through brick and stone, the masonry gives the fungus no food, and its limited ability to move water can be cancelled out by good ventilation. It depends on an outside source such as a leak, condensation or a damp wall, according to PCA fungal biology guidance. See our guide to dry rot and wet rot.

Why must the water be stopped before treating wet or dry rot?

Because fungal decay halts once timber is dry enough. BRE scientists found that decay will cease if the moisture content of the wood falls below about 20 per cent, and the PCA puts it plainly: "Without water the fungi can not grow." Its guidance says control "is always focused on elimination of free water", with fungicides only protecting vulnerable timber in the short term.

BRE also questions soaking masonry with fungicide, which adds water and slows drying; chemicals "must not be regarded as a substitute for getting the building dry".

That is why timber work is part of damp proofing in Oxford rather than pest control. Oxford Damp Specialists checks the sources the PCA lists for wet rot: roof leaks, flooding, poor maintenance, poor ventilation, building defects and groundwater. Often the fix is a penetrating damp repair outside before any timber is touched.

Why do joist ends rot inside solid brick and stone walls?

Because the end of the joist is buried in masonry, and wood built into masonry is where the PCA says wet rots are usually found. When rain gets into the wall through failed pointing, a leaking gutter or raised ground, the bearing stays wet. In older Oxford houses this is common construction: the Council's Heritage Retrofit Guidance says that up until the 1930s houses were most commonly built with solid brick walls and mostly lime-based mortars and plasters.

A timber floor joist built into a damp stone wall: the joist end is dark and cracked with wet rot, and pale dry rot strands run up the masonry to a fruiting body higher on the wall — Wet rot stays in the wet timber; dry rot can spread across damp masonry to reach wood further away.

A wet bearing is also the deathwatch beetle's ideal home, as Ridout notes. Cement repairs can make it worse: SPAB says hard cement renders hinder evaporation, and that cement mortar in timber-frame cracks "will retain moisture and encourage decay". The same Council guidance warns that inappropriate alterations "could otherwise lead to a building up of damp, mould or dry rot".

The repair follows the water: dry the wall, repoint in lime where needed, cut decayed timber back to sound wood and splice or support the joist end.

Should the air bricks under a suspended timber floor ever be blocked?

No. Oxford City Council's heritage retrofit guidance says that for suspended timber floors, air bricks and ventilation should not be covered up. Historic England notes that timber suspended ground floors can stay damp and decay, and that external ground levels build up over the years, opening moisture routes that were not originally there.

A blocked air brick leaves the void under the floor still and humid, which suits rot. We check every air brick, look into the void and test joists and wall plates. On timber a damp meter gives reliable readings, according to RICS; on brick and stone it can give false highs.

How much does woodworm or rot treatment cost in the UK?

These are national yardsticks from other publishers, not our prices. Oxford Damp Specialists confirms a price when you book, once the extent is known.

Work	National range	Source
Woodworm treatment, average	£500 to £1,000	Checkatrade, prices June 2024
Inspection for woodworm	£80 to £250	Checkatrade, June 2024
Loft treatment, 3-bed house	£400 to £900	Checkatrade, June 2024
Wet rot, minor	£500 to £1,000	MyBuilder, undated
Wet rot, moderate	£1,000 to £2,500	MyBuilder, undated
Dry rot, small and localised	£500 to £1,500	MyBuilder, undated
Dry rot, whole property	£5,000 to £12,000+	MyBuilder, undated
Joist replacement	£250 to £350 per joist	MyBuilder, undated

The biggest variable is how much timber has to come out. The woodworm treatment cost guide explains when no treatment is needed at all.

Common questions

Old flight holes in my floorboards: is treatment needed?

Not if the infestation is no longer active. Treatment is only justified when fresh holes or bore dust show current activity, and much of the timber in Georgian and Victorian houses resists furniture beetle.

Can wet rot be left alone because it is not dry rot?

No. Wet rot weakens timber, which then has to be cut out and replaced. What sets dry rot apart is its ability to cross masonry and colonise more timber.

Are timber repairs in a listed Oxford house subject to consent?

Possibly. Oxford City Council says consent covers any work, internal or external, that affects a listed building's special character, including repairs that replace important fabric, so check before historic timber is cut out.

What time of year suits woodworm treatment?

Early spring to late summer, when adult beetles emerge, according to the PCA. Activity should be proved first, which can mean a check during that season.

Sources for this page

Before you call

A few details let us narrow down the likely cause on the phone.

Postcode and the rough age of the building
Which rooms and walls, and how far up
Whether wet weather or cold snaps change it
Where any mould is growing
Owner, tenant or buyer, and any deadline

Ring 01865 537413 Arrange a survey

Woodworm and rot treatment outside Oxford

Need woodworm treatment outside the city boundary? Each town page below looks at that town's houses, ground and rivers, and our damp proofing in Oxford page explains how we work.

Woodworm and rot treatment in Didcot

OX11

Woodworm and rot treatment in Bicester

OX26, OX27

Worth reading first

What does woodworm treatment cost?

Those tiny round holes in your floorboards may be decades old, so prove the beetles are alive before paying anyone to spray.

Dry rot or wet rot: how do you tell them apart?

Strands creeping over brickwork or a soft joist end: how to read the signs of rot, and why the water decides the repair.

Related work

Basement and cellar tanking

Oxford sits on gravels where winter groundwater can lie under a metre down, so a dry cellar needs the right protection type.

Shall we call you instead?

Your name, number and the property postcode are all we need. A sentence about the room and the wall makes the first call quicker. Or ring 01865 537413.

Woodworm and rot treatment in Oxford

Tell us about the timber