Looking after a listed building is always a challenge. Some come into possession of a structure that is empty and not in good shape, requiring restoration work with the added requirement that it is not just made to look as good as new but to look just as it once was.
Even if the task is simply one of ongoing maintenance, the job still needs to be carefully carried out to ensure the work maintains the structure and appearance of the property.
The strictness with which this applies depends on the listed status. In England, 91.7 per cent of buildings are Grade II, while 5.8 per cent are Grade II*, making them of special interest and just 2.5 per cent are Grade I, the most exceptional buildings and the ones with the tightest restrictions on what can be done with them.
Overall, around 500,000 English structures are listed and a large proportion of these are built largely or wholly from brick. Good examples include a myriad of Victorian buildings across the country, the largest being the Stockport Railway viaduct, with over 11 million bricks.
Suffice to say, if you need a brick cleaning job on a listed building you probably won’t have anywhere near that many bricks to look after, but it is still vital that this is done.
It is not just that allowing grime, mud and moss to cover them is aesthetically detrimental, though it is certainly that; but pollution can also wear away at bricks, with particles and acid rain taking their toll. Plants like moss, algae and lichen can also damage brickwork.
There is also the fact that despite their clay composition and general resilience in Britain’s changeable climate, rainwater will eventually start to cause bricks to deteriorate.
Other problems can include the presence of corroding metal components, while past cleaning methods may have done some damage. For example, high-pressure jet blasting can damage older bricks, which historic listed buildings are, by definition, more likely to have.
The best solution for this is to use gentler methods of cleaning such as steam cleaning. This can gradually and slowly remove particles of pollution, layers of acid, moss, lichen and other plant growth without causing further structural damage.
It may be that the right treatment will vary on different parts of a building. For instance, moss tends to grow on the north side of buildings, which gets daylight but little direct sunlight except on summer mornings and evenings. That means you need to pay specific attention to this on the north side and will be spared the problem elsewhere.
Equally, it may be that some angles and the presence of other structures nearby will mean some parts of a building are less exposed to heavy rain, while the level of pollution damage will depend on geography; an urban location in an industrial city will be affected more than a rural one, especially if it is not downwind of pollution.
Nonetheless, if you are keeping an old brick building in good order and the listing prevents you from covering over or painting brickwork, it is important that whenever it is cleaned, it is done in the best way to help preserve it as well as possible.