BUILDING DEFECTS AND DAMP
Timber & Damp Surveys
At Blackacre we use expensive calibrated inspection equipment (not a standard two-pin 'moisture meter'!) to identify the cause of damp. This will usually involve taking accurate measurements throughout the building for diagnosis of the problem so we can advise you on the most effective means of remedy.
All surveys are undertaken using an arsenal of inspection equipment, including thermo-hygrometer, thermal imaging camera, surface temperature probe, borescope and conductivity meter.
Unfortunately, many surveyors are not trained in the mechanics of damp and will only use a basic 'moisture meter' on their inspections. Even if the surveyor uses this properly, it gives very little reliability as to the actual problem and cannot confirm the presence of damp.
We use all the equipment noted above to provide information on the levels of Relative Humidity (RH %), Absolute Humidity (AH g/m3), and Dew Point (Td °C). In additional to these we can use our thermal imaging camera and borescope to understand the sources of moisture within the building fabric hidden from view.
Types of Damp
All properties will experience damp at some point in their life. It is completely expected that moisture will try to ingress and equalise with dry elements of a property. However, if not suitably maintained and repaired, damp will cause damage to a property and its materials, and in some circumstances, result in significant costs to repair.
This form of damp is typically caused when a source of water ingresses a property from external sources such as rain through cracks and weakness in the fabric, or from internal sources such as service pipe leaks penetrating through floors and ceilings.
It is essential that any source of water ingress is repaired immediately as any prolonged contact with water will cause materials to degrade. In some circumstances causing further issues which will be costly to repair. For example, the rotting of timber can, in some instances, spread to other timbers causing structural weakness and large amounts of timber to be replaced.
Condensation occurs when a surface's temperature drops below the ‘Dew Point’ which means the air is no longer able to retain moisture and will instead condense onto the cold surface.
An example of this would be a room with a reasonable temperature of 20°C but high Relative Humidity of 80%. At these conditions the Dew Point is 16.4°C, meaning any surface below that temperature is susceptible to condensation (which is most likely to happen with a traditional solid wall), and if this is prolonged, discolouration and mould will appear.
When Relative Humidity is high, the best way to stop condensation is to ensure proper space heating and ventilation are provided, these will ensure stable conditions so that surfaces remain at a reasonable temperature and humidity levels are reduced.
Using the example above, what happens when this Dew Point temperature is reached, but not on an internal surface, but within the fabric of a building? This is called interstitial condensation and typically occurs within walls and roofs.
The illustrations (shown here) are useful Dew Point profiles of a solid wall with external insulation and a solid wall with internal insulation, that clearly show the principal of interstitial condensation.
As air and water vapour naturally diffuse through the wall, its temperature will cool, causing the relative humidity to rise. This can result in the Dew Point being reached and condensation occurring within the wall.
This can be problematic for a number of reasons, not least that wet walls are less thermally efficient and will loose heat faster. It can also result in freeze/expand action which will 'spall' the brick face.
There are particular concerns surrounding cavity wall insulation which is packed into the cavity, preventing any ventilation. When condensation occurs to the internal face of a cavity, it relies on ventilation to omit the vapour. Otherwise there will be a build up of moisture which can cause major damage such as corrosion of wall ties and delamination of the brickwork.
Ground Moisture (Rising Damp)
Although there is a lot of hype surrounding Rising Damp (mainly within the damp proofing industry...), at Blackacre we take a more holistic view on the discolouration and salt deposits at the base of your wall. We would rather follow the science and our own professional experience, which indicates 'Rising Damp' is actually not the cause and is highly likely to be caused by something else.
All properties experience a degree of movement over their lifetime, some more than others and some more serious. Whether it be an older period building or a newer property, cracking can occur for a multitude of reasons. Poor foundations, ground conditions, leaking drains or new works, just to name a few.
Blackacre take a holistic approach to building cracking and consider all factors that could be an influence. We always deal with the problems in a practical manner and ensure the client is aware of the level of risk and best route forward.