Conservation Science

The right time to use Westox Cocoon in the UK


We have recognised the United Kingdom is now in need of immediate intervention and according to conservation science our traditional built properties are in the danger zone for serious salt attack/decay.

According to the Department of Environmental and Heritage in Australia, the United Kingdom has a cooler and wetter climate than Australia and so the rate of transpiration of moisture through walls is lower. Condensation is a more significant problem, and the misdiagnosis of damp problems as due to rising damp is common. In contrast, the hotter and drier, temperate Australian climate promotes rapid evaporation from wall surfaces and hence greater rates of transpiration of moisture due to rising damp.
 
Historically in the United Kingdom we have tended to focus on the damp, rather than on the salt. Yet both must be dealt with if our buildings are to be maintained in the long term. Failure to understand this has led to remedial treatments that may have successfully inserted a new damp-proof course but haven’t stopped decay, because salts are left in the walls above the new DPC and continue to cycle in and out of solution with changes in humidity. Although the main source of moisture is removed (and the further supply of salt reduced) decay will continue, albeit at a slower rate. Best practice treatment of salt damp involves removal of salts as well as cutting off or minimising the damp.
 
Consider a hypothetical case of a 140 year old traditional sandstone built building with lime mortar. There is no damp-proof course and not a lot of dampness in the walls. On the inside the plasterwork is in good condition with only a few small areas of blistering beneath paint coatings. It is tempting to think that as the house has lasted 140 years, the decay will not be much worse after another 20 or 30 years. Postponing action on this basis would be wrong, please see Salt Graph below, based on conservation science and an understanding of the rate of decay of materials.

Salt level before treatment with Westox

There is a long period of almost no decay (in this case about 100 years) during which time salts are slowly accumulating within the Sandstone. Only then do they fill the pores sufficiently to cause significant salt attack decay. By the time the house turns 140 years the decay has accelerated to near its maximum rate and in only ten more years the decay will be twice as bad as it is now. There are two important lessons from this. The first is that procrastination is not an option and something must be done.

The second is that, by reversing the decay and its cause, it will be possible to effectively reset the position on the graph back to a point where there is little decay. This is shown in the 2nd Salt Graph which assumes that we have reversed the decay and removed the immediate cause (by taking the salt out) so as to reset the decay clock  back.

Salt levels affter treatment with Westox Cocoon

Importantly, this approach buys time. By reducing salt concentrations so that decay is minimised, our traditional buildings have time to review its moisture regime and to determine an appropriate course of action, which may or may not include insertion of a damp-proof course. Below is an example of a charted example of a Westox Cocoon Trail Salt Reduction.

Westox Cocoon Salt Reduction Chart