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Architectural Conservation



Understanding and stabilising environmental conditions within a building is a powerful means of decelerating the decay of both the fabric and its contents.

The environment generates several factors of deterioration, all of which may impact separately, but which will also have combined effects. These factors include light levels, the presence of liquid moisture and water vapour, pollution (including salts), and fluctuations in environmental conditions (temperature and relative humidity).
Building survey

An internal and external inspection will consider the stability and efficiency of the building fabric (roof, rainwater goods, pointing, drainage) and identify incidents of current or historic water ingress. Materials that are detrimental to the stability of the building will be identified, and factors such as heating, lighting, ventilation and access reviewed.

Environmental monitoring with Humbug data loggers (Hanwell Instruments)

Following a buildings survey, Hirst Conservation may recommend the use of Humbug data loggers to monitor environmental conditions inside and outside a building over a period of time. The results are interpreted to establish daily and seasonal fluctuations in temperature and RH, allowing Hirst Conservation to:

  • Provide a profile of conditions inside and outside the building, to establish the interaction of the internal and external environment
  • Identify potential hazard periods in fluctuations, for example, condensation events – and mobilisation of salts
  • Identify cyclical salt crystallisations (by identifying the relative humidities at which salts will move in and out of solution (their equilibrium RHs)

Moisture and Salt Profiling

Hirst Conservation undertakes moisture and salt profiling of historic fabric using protimeters, capacitance and/or carbide meters. These instruments can indicate both salt and moisture content of the material being analysed.

Carbide measurements do require a sample of the material but they provide absolute values of percentage moisture by weight of fabric analysed. The carbide meter can also be used to measure the hygroscopicity (hygroscopic moisture content) of the sample caused by any hygroscopic salts present.
Additional, non-intrusive salt profiling can be achieved by qualitative identification and their relative concentrations, determined using Merckoquant test strips for nitrates, sulphates and chlorides.


The results of the buildings survey and environmental monitoring will be interpreted and recommendations provided for the development of an appropriate strategy to stabilise the building’s environment.