RICS Surveyor in France. Go ‘green’ with period property and ventilate, ventilate, ventilate!!!

As a RICS Surveyor in France, we see that one of the largest causes of damage and degradation to houses is caused by the presence of damp. This in turn creates the perfect environment for wood rot and wood boring insects that can cause a huge amount of damage to timber structures. Damp in masonry may cause spalling and degradation of stonework and ‘blowing’ of render, in addition to corrosion of steel reinforcing rods within concrete structures. As the steel rusts it expands and the concrete surrounding the steel becomes detached. This compromises the structural capability and ultimately leads to failure.

RICS Surveyor in France. 'blown' concrete around rusting reinforcing rods

RICS Surveyor in France. ‘Blown’ concrete around rusting reinforcing rods

As a RICS Surveyor in France we see particular examples of damp being introduced to buildings, often as a result of modern building materials and repairs being inappropriately applied to houses of traditional construction.

However, there is an enormous and ever increasing promotion of so called ‘energy saving measures’ that seek to reduce energy consumption and CO2 emissions from houses. Despite the degradation caused by damp, ironically these initiatives often promote the eradication of drafts with the installation of modern windows that seal without any air gap, the introduction of draft seals and huge amounts of insulation to lofts.  Whilst such advice is well intentioned, sadly the logic is flawed and counter productive when applied to traditionally constructed properties. The reason is that older properties often have solid stone walls and floors, without damp proof course or cavity. The design on construction was to allow the damp to escape from the house via gaps in windows and beneath doors and through vapour permeable materials. This allows the house to ‘breathe’ and remain dry. This in turn allows the house to remain free from wood rot and insect attack etc.  

RICS Surveyor in France. Modern window restricting ventilation

Modern window restricting ventilation

Even ignoring damp ingress through leaks etc, the production of water vapour can be huge from every day living including breathing, showers, cooking etc. From these every day activities, 4 occupants within a house will typically produce approximately 5 litres of water per day. So 150 litres of water carried within a much larger volume of air needs to be ventilated out of the house every month, otherwise water will be absorbed into the plaster of walls and timber joists etc. In addition of course the natural dampness from the ground, and building fabric needs to be extracted from the house.

RICS Surveyor in France. Ventilation

Damp air condensing on window. A similar process takes place to non-permeable materials within walls etc but is concealed from view.

Ironically the result of the ‘energy saving measures’ can result in reduced ventilation that in turn can result in degradation of the building fabric. This may then require extensive timber and other repairs to be needed. These repairs including the replacement materials are likely to result in the consumption of much more energy and production of more CO2 emissions than the ‘energy saving measures’ could ever have achieved. Furthermore, the financial cost of the repair works is likely to be significantly more than any perceived energy cost saving.

As a Surveyor in France, we understand the logic of traditional and modern construction methods. Our Surveys in France take account of the construction method adopted in the house. This will also influence our corresponding approach and advice as to ventilation. When undertaking RICS Surveys we also provide forward looking recommendations and care plans that will help keep the structure dry and thus naturally resilient to wood rot and insect attack, and also preserve the masonry. Accordingly the house will also be more environmentally sustainable. These principals will be valid at the date of the Survey Report and equally valid for generations to come.


Structural Survey in France. Traditional strategy to treat wood rot and provide future natural defence

Structural Survey in France – this brief summary presents the traditional strategy for the treatment and prevention of wood rot within buildings.  When undertaking a Structural Survey in France we adopt this approach in the recommendations. It is very similar to the approach for addressing wood worm.

The process of wood decay is an essential part of the ecosystem, converting dead wood into humus. Were it not for this process, the forest floor would be full of dead trees. Wood decay is achieved by a combination of wood boring insects and wood rot.

Structural Survey in France - wood rot

Damp resulting in wood rot.

As the rot develops, it softens the timber allowing it to absorb more moisture. This makes it an attractive environment for wood boring insects that will further degrade the timber. Left unchecked, the rot will develop and compromise the structural capability of the timber. This may lead to full structural failure. Remedial work may be very expensive and disruptive if replacement timber is required, especially if the timber is recessed behind masonry and plaster etc.

There are 2 key types of fungal attacks to wood, namely wet rot and dry rot. Both require elevated levels of moisture to be present in the wood in order to survive. However, dry rot requires less moisture to be present so is sometimes of more concern as it can flourish and quickly spread even in less damp conditions.

If the wood is dried to adequate levels (through addressing the source of the damp, combined with ventilation), existing rot will die in the drying process. Importantly the dried wood will become an unattractive environment for future fungal attack and naturally resistant to future attack.

When undertaking a Structural Survey in France, in addition to reporting any damp issues that may be present, we also detail remedial options including repair works and modifications to address damp. We also provide care plans such as increasing ventilation, particularly in loft space where ventilation may be compromised. This will allow the overall structure to remain dry, including of stone walls that in turn will draw moisture away from timber embedded within the wall.

An alternative approach to combat wood rot is to use modern chemical treatments. However, some timber may be inaccessible to treatment, for example concealed behind masonry or plaster. Where chemical treatment is recommended, this should always be undertaken in tandem to addressing any damp issues, with the objective of drying all areas.

We are firm believers in the traditional approach of keeping the structure dry to effectively combat wood rot, and importantly provide a natural defence for the future. This approach is centuries old in the making will last for centuries to come.