Wood rot is a common problem in homes with damp. However, it’s not wood that causes problems, but moisture. Wood is an excellent material for building as it’s resistant to most biological attacks as long as it remains dry. However, if it’s exposed to water over a prolonged period, it can be vulnerable to decay from wood-rotting fungi.
Fungal attack generally initiates from airborne spores. It can also be a problem if pre-infected timber has been used in building construction. If you’re unsure whether your wood could be infected with rot, it’s better to be safe than sorry and treat it with a fungicide.
Why Does Wood Rot?
Most wood rot happens as a result of rainwater entering the fabric of the building, or due to rising damp. As such, a thorough external survey is the first step. The problem could stem from missing or defective roof tiles or slates, blocked guttering, damaged roofing membranes, a defective damp proof course (DPC) or a host of other sources. Internally, problem areas can include cellars and basements, skirtings on damp walls, joists or suspended walls with inadequate underfloor ventilation and bearing ends of timbers in non-cavity walls, among others. As fungi require at least 20 percent moisture content, they are unlikely to be found in internal timbers unless design or building issues have led to water ingress or condensation.
Symptoms of Wood Rot
Symptoms of wood rot can include the following:
- A ‘mushroom’ smell and/or fungus growing on the wood.
- A softening or disintegration of wood
- A ‘hollow’ sound when wood is struck with a hammer
- Discoloration of wood
While not all fungi cause wood rot, the presence of any fungi is an indication that the wood moisture content is too high, making it vulnerable to wood-rotting fungi.
How Fungi Rot Wood
The problem with wood-rotting fungi is that they break down the cell walls of wood, causing them to lose strength. Wood-rotting fungi found in buildings can be divided into two main categories: white rots and brown rots. White rots cause wood to become lighter in colour and fibrous in texture, without any cross-cracking. Brown rots cause wood to become darker and crack both across and along the grain. Extremely decayed wood will crumble to dust when dry.
All these rots are referred to as wet rot, except for the brown-rot, Serpula Lacrymans, which is known as dry rot. Dry rot is less common than wet rot but can be more devastating as rot can spread through parts of the structure that are relatively dry. Wet rot tends to occur mostly at timber joist bearings in external walls: at the sole or head plates rather than in the studs.
Dealing with wood rot
Get problems diagnosed by a member of the PCA (Property Care Association) as there can be complex causes (sometimes multiple) and you don’t want to make an expensive mistake through misdiagnosis.