Timber Defect Information Guide
Timber decay in buildings will only occur if the timber becomes sufficiently wet. Once the problems that allowed the timber to become wet are resolved, the timber will begin to dry and the decay will be controlled.
- chemical treatments should only be used as a means of controlling decay whilst the timbers are dried
- moisture meters are designed to evaluate moisture is timber, not damp walls
- wood rotting fungus will not decay dry timber
- death watch beetle prefer oak
- dry rot is mainly found in softwoods
- the holes that you see on the surface of timbers are exit holes (flight holes)
- sapwood in a living tree is resistant to decay but vulnerable once incorporated into a building
There are occasions when the targeted use of chemical treatments is justified.
However, the treatments should be specifically tailored to the defect, why use a dual insecticidal and fungicidal treatment when only common furniture beetle is present with no evidence of fungi, always targeted and never blanket treatments.
Published figures indicate that wood-rotting fungi will not decay timber with a moisture content below 22% and wood-boring beetles will not be successful in timbers with a moisture content below 12%.
Timbers found in different parts of a building will display differing levels of moisture content. In a central heated house , we find that floorboards and joists on the ground floor level have an average moisture content of 18.5% with readings of 11% found in timbers of the first floor level.
These readings change dependent on the time of year that the timbers are inspected. This is most dramatically witnessed when assessing timbers within the roof void. In the colder months, the moisture content of roof timbers can be elevated to 18-19% before receding to approximately 10% in the summer months
Common causes of timber decay
Generally, we find that the most common causes of timber decay are as follows:
Design
In many older buildings, structural timbers are embedded into external walls and encased into solid floors, which is a common cause of timber decay.
Alterations
We often find that ill advised alterations have facilitated timber decay.
This is regularly seen when sand and cement rendering has been applied to the exterior of the building, trapping moisture and elevating the moisture content of timber window lintels and embedded joists, leading to their decay.
Maintenance
Blocked gutters, missing roof tiles and leaking pipes will all allow water to ingress into the fabric of the building, which will cause affected timbers to decay if the problems are not noticed or corrected.
Wood-boring insects
Many old houses will have evidence of some form of beetle activity, which will mostly be historic and will have died out years ago.
Timbers that were introduced into the building during construction may have had a high sapwood (high in nutrients) content and would have been susceptible to beetle infestation. Generally, once the sapwood has been depleted and moisture levels within the timbers remain stable, the beetle infestation will die out. The beetles will only infest the heartwood section of the converted timber if it has been modified by fungal decay.
Fungal decay
Fungi require higher levels of moisture than beetles to develop.
The main fungi that affect timber in buildings can be separated into two groups, white and brown rots.
White rots have a bleached, fibrous appearance and a substantial loss in weight is evident in the timber. Timbers decayed be this group of fungi generally require a higher moisture content than timbers decayed by brown rots.
Brown rots are synonymous with the darkening of the timber, cuboidal cracks and are mainly found in softwoods.
Solutions
Below are a few simple measures which may assist you in addressing a timber defect you may have within your property.
If the moisture levels of affected timbers can be reduced to within the safe parameters that have already been discussed, both fungal and insect activity will cease. However, consideration should then be given to any structural implications caused by the decay.
If you notice timbers with beetle flight holes, the following tests will help you assess if they are active.
Fix a sheet of paper close to the surface of the suspect timbers and if the paper is punctured by an emerging beetle, then the infestation is active. Although not aesthetically pleasing in your living room, another method we use to assess the severity of beetle activity is to hang a tray below the timber and record the number of beetles found.
Most wood-boring beetles found in the U.K, emerge from the holes between March and September, some can appear all year round , dependent on species and environmental conditions.
As we have said before, dry timber does not decay, therefore, the key to successfully bringing the decay under control is to find the source of moisture, undertake corrective repairs that resolve the defects whilst starting to dry the timbers.
If you are concerned about beetle or fungal decay and would like to discuss it with a surveyor, please call 0871 218 5767.