Wet Rot vs Dry Rot: Signs, Causes and Timber Repairs
Wet rot and dry rot are both forms of fungal timber decay, but they behave differently. Early diagnosis matters because the visible damage may be only part of the problem.
WHAT CAUSES TIMBER ROT?
Fungal decay needs moisture. Common sources include leaking roofs or pipes, penetrating damp, blocked ventilation, high ground levels, condensation and damp subfloors.
The first priority is always to find and control that moisture. Replacing timber without fixing the cause can allow decay to return.
WHAT IS WET ROT?
Wet rot normally remains close to a persistently damp area. The timber may feel soft or spongy, crack along the grain, become darker or lighter, and lose strength.
It is commonly found around leaking windows, roof defects, damp skirting boards, poorly ventilated floors and plumbing leaks. The decay usually becomes inactive once the timber is properly dried and the moisture source is removed, although structurally weakened wood may still require repair or replacement.
WHAT IS DRY ROT?
Dry rot is caused by a particular fungus that can spread through timber and across masonry in suitable damp, poorly ventilated conditions. Signs can include brittle brown timber, cuboidal cracking, white or grey fungal growth, strands and fruiting bodies.
Despite its name, dry rot also requires moisture. The term does not mean it develops in dry timber.
SIGNS THAT NEED INVESTIGATION
Watch for:
• springy, uneven or soft floors
• skirting boards that crumble when pressed
• cracked or blistering finishes beside timber
• persistent musty odours
• fungal growth or fine strands
• distorted doors or windows
• small flight holes or frass that may also indicate wood-boring insects
• recurring damp or mould in the same room
The presence of holes does not automatically mean an active woodworm infestation. Their size, shape, debris, timber species and surrounding conditions need assessment.
HOW TIMBER DECAY IS DIAGNOSED
A proper inspection looks at the timber, moisture content, structural condition, ventilation and nearby building defects. Concealed areas beneath floors, behind plaster or inside roof spaces may require further access.
Not every affected member needs total replacement. Localised repairs may be appropriate where sound timber remains and the structure can be made safe. Severely weakened or extensively decayed timber may need replacement, sometimes with additional structural advice.
WHAT PROPER REPAIR INVOLVES
A lasting repair usually follows this order:
• stop the moisture source
• improve ventilation and drying conditions
• expose enough of the area to establish the extent
• remove or repair timber that has lost adequate strength
• apply an appropriate treatment only where required
• reinstate floors, plaster or finishes after the area is ready
Treatment products do not compensate for unresolved leaks or permanently damp conditions.
WHEN TO ACT
Do not ignore a bouncy floor, crumbling skirting or persistent musty smell. Timber problems are normally easier to contain when investigated early.
Renovani assesses damp-related timber decay and woodworm across Sussex and Kent.
Timber service: https://lanternfish-begonia-586n.squarespace.com/timber-treatment
Book a £50 survey: https://lanternfish-begonia-586n.squarespace.com/surveys-50
