Timber
Wet rot investigation and timber repairs
Identifying and repairing timber decay caused by sustained high moisture content.
Where we find it
Wet rot follows water, and water follows maintenance
Wet rot is fungal decay in timber that has become and stayed wet. Coniophora puteana is the species most often involved, and it needs distinctly wet timber rather than merely damp. It does not spread through masonry, so it is generally confined to the area the water reaches.
The positions we find it in are predictable, because they are the positions water reaches:
Window and door joinery, particularly cills, lower rails and glazing bars
Joist ends and wall plates built into damp external walls
Floor timbers below leaking bathrooms, showers and kitchens
Timber near leaking heating or supply pipework
Roof timbers beneath slipped coverings or failed flashings
Timbers in subfloor voids with blocked or absent airflow
Fascias, soffits, bargeboards and timber behind defective rainwater goods
Stair strings and skirtings against damp masonry
Because the decay is limited to the wet zone, the repair is usually proportionate — provided the water is genuinely stopped and the timber is allowed to dry before anything is closed up.
What the issue is
Wet rot is decay of timber that has remained wet. It stays localised to the damp timber, so correcting the moisture source is the primary remedy.
Common symptoms
- Soft, spongy or darkened timber
- Cracking along the grain
- Localised decay near leaks
- Failing window joinery or door frames
Likely contributing factors
- Leaking rainwater goods
- Failed window or door seals
- Plumbing leaks
- Timber in contact with damp masonry
- Poor ventilation
Conditions that may be mistaken for it
- Dry rot, which behaves differently
- Surface staining
- Old mechanical damage
How the issue should be investigated
- Locate the extent of decay
- Identify and confirm the moisture source
- Record moisture content
- Assess structural significance
Potential treatment or repair options
- Repair of the moisture source
- Cutting out and replacing decayed timber
- Splice repairs to joinery
- Preservative treatment of adjacent sound timber
- Drying and making good
When treatment may not be appropriate
- Where decay is superficial and the timber is drying
- Where full replacement is proposed but a splice repair is adequate
Factors affecting the cost
- Volume of timber replacement
- Joinery matching requirements
- Access and temporary support
- Decoration
What to expect during an inspection
An inspection of the affected timber and surrounding structure, with moisture readings and photographs.
How we deal with it
Stop the water, then repair the timber
- 1
Trace the water
The defect responsible is identified — roof, rainwater goods, joinery, plumbing, penetrating damp or airflow — and confirmed rather than assumed.
- 2
Assess the timber
Moisture content measured, decayed timber probed to establish loss of section, and structural significance considered where joists, plates, lintels or bearings are involved.
- 3
Correct the defect
The repair to the building fabric comes first, so the replacement timber is not being installed into the same wet conditions.
- 4
Repair or replace
Splice repairs and resin systems where part of a member is sound; full replacement where section loss is significant, with isolation from damp masonry and airflow around new timber.
- 5
Dry and ventilate
The void or structure dried, and airflow restored where it had been lost, so the conditions that allowed decay are not simply covered over.
Blocked air bricks are one of the most common contributors we find in suspended timber floors, and one of the cheapest to put right.
Related work
Related timber work and reading
Timber preservation
Decay and insect activity assessed against the moisture conditions that made the timber vulnerable.
Dry rot investigations
Serpula lacrymans identified, its extent established and the moisture source it depends on removed.
Woodworm investigations
Active infestation told apart from historic damage, so timber is only treated where treatment is justified.
External damp-related repairs
Pointing, render, rainwater goods and ground levels put right so water stops reaching the wall.
Damp surveys and moisture investigations
What a professional damp investigation covers, what the instruments can and cannot establish, and what your written report contains.
Why air bricks and subfloor airflow matter
How a blocked airflow path turns an ordinary suspended floor into a decay risk.
Where we work
Wet rot investigation and repair across Bedfordshire, Northamptonshire and Cambridgeshire
Wet rot investigation and repair is carried out across our operating area. Choose your county or town to see the work we do locally, the postcode districts we cover and how to arrange an inspection.
Frequently asked questions
Next step
Not sure which inspection you need? Start with a few questions.
Tell us what you are seeing and we will set out what is likely, what is uncertain and which inspection would answer the question. Speak to us on 0333 335 6152 if you would rather talk it through.