Do's and Don'ts of Timber & Damp Treatment

By Graham Coleman at www.buildingpreservation.com

Do:

• Do regularly check building for water leaks from guttering, also check for defects in pointing, the roof and other structures (e.g. lead flashing) which could allow water ingress. Remember dry wood doesn't rot. Make sure therefore the building is regularly inspected and maintained for any likely signs of water penetration. Internal plumbing or wet heating systems that leak are also a source of water that can lead to rot, etc.
  
  
• Do be aware that if timbers remain persistently damp or are very slow drying they will be at risk of rot developing. Where such dampness is encountered and it is not cost-effective to remove then some form of suitable targeted preservative treatment may be used to minimise the risk of rot developing. It is also very important to discover why and where the moisture is coming from and considering undertaking any building works to eradicate the problem now or in the future.
  
  
• Do be aware that certain levels of dampness in older properties may be acceptable. However, where this is deemed so any timber in contact with that dampness should be protected from it to prevent the risk of rot.
  
  
• Do evaluate any dampness problems carefully. For example if the dampness persists through the warmer months of the year (April-October) then it is unlikely to be condensation. Look for other sources including rising damp, penetrating damp, plumbing leaks, etc.
  
  
• Do use materials that are sympathetic with those currently forming the fabric of the property. For example replace defective old lime mortar pointing with lime based materials and not with cement based materials. But -
  
  
• Do understand that replacing salt contaminated original old plasters with similar materials could lead to similar decorative problems in the longer term. Discuss any such problems with a specialist conservationist/specialist surveyor.
  
  
• Do ensure adequate ventilation during the colder months of the year. Remove water by extraction, eg, extractor fans, from areas of high moisture production, eg, kitchen and bathroom. Try to maintain at least a low level of background heat to most rooms.
  
  
• Do ensure that earth or other materials do not pile up against walls above the natural internal floor level. Ideally ground level should be at least 150mm/6" below internal floor level. To achieve this it is sometimes necessary to create drainage channels around a building.
  
  
• Do be aware that some properties are in areas of high ground water levels and will be more prone to dampness. This can sometimes be tackled by diverting ground water away from or around the building by land drains. Such a solution can often be used uphill of a property built into a slope.
  
  
• Do ensure rainwater can flow freely away from the base of the building. If downpipes run straight into ground or underground gullies with no access, consider installation of rodding eyes to facilitate periodic clearing.
  
  
• Do be aware that heavy plant growth on the face of buildings can lead to long-term water penetration.
  
  
• Do ensure that if you are having a period property surveyed for purchase the individual employed to undertake the survey is familiar with the contents of the RICS Red book concerning the valuing of historic buildings for mortgage purposes. It is preferable that your surveyor has a diploma in Building Conservation and/or is accredited in Building Conservation.
  
  
• Do use a specialist surveyor if dampness persists. Use a member of the BWPDA who has the nationally recognised CSRT qualification (or CRDS/CTIS qualifications), provided the surveyor is familiar with your type of property and construction. Use a company that charges for surveys and always get competitive quotes. Thoroughly read all reports. The surveyor should not have a vested interest in his/her recommendations.
  
  
• Do ensure that the source or cause of dampness has been properly identified and dealt with before tackling other repairs.
  
  
• Do be aware most wood boring insects cannot be eradicated simply by ventilation.
  
  
• Do be aware not all wood boring insect activity needs treatment, eg, old damage, innocuous insects, forest insects.
  
  
• Do be aware that randomly applied surface treatment is usually ineffective in eradicating active infestation. Many wood boring insects will survive in hidden or difficult to reach areas, this requires a targeted approach.
  
  
• Do evaluate the structural integrity of infected/rotted timbers prior to any treatment that is deemed necessary. Only replace timbers that have lost their structural integrity. Consider the form of repair, as simple replacement is often only one of several possible solutions.
  
  
• Floor bricks, pamments, and flagstones were often laid directly on to earth, chalk or lime in older properties which allows ground moisture to slowly evaporate. Do not automatically assume that such floors need to be dug out and replaced with a dpc and concrete. If you do not have a damp floor leave it or simply remove lino and/or carpet to allow the floor to dry out before considering any actions. Also ensure floors laid on earth, chalk or lime are not sealed with a synthetic sealant and consider traditional alternatives such as lime water, turpentine and beeswax or linseed oil. The joints between the flooring material should be left untouched.