There are a number of reasons why building owners may wish to carry out cleaning of the exterior masonry to their building and these include;
- For aesthetic purposes where the intention is to improve the appearance of the building to make it look newer and well maintained. Dirty buildings generally look like they have been neglected.
- To protect the surface of the masonry from being stained and eroded by chemical pollutants, algae, moss, mildew etc.
- To reveal defects and to prepare the building for repair and redecoration.
The results of masonry cleaning can be quite spectacular.
There are a number of different ways in which masonry can be cleaned and these include jet washing, steam cleaning, dry abrasive cleaning, acid cleaning, chemical cleaning, etc.
High pressure steam cleaning seems to be one of the more popular methods of masonry cleaning. It is often preferable to jet washing as it uses less water and the high-pressure steam is more effective in removing dirt and grime. It is also preferable to chemical cleaning as it avoids the use of chemicals and is therefore more environmentally friendly. Dry abrasive cleaning may be preferable in certain circumstance but should be undertaken with care to ensure that it does not erode the surface of the masonry.
If the intention is to clean historic / listed buildings a listed building application will need to be submitted and the method of cleaning approved to ensure that the cleaning process will be sympathetic to the building and that it will not cause any damage.
It is always advisable to undertake cleaning samples to a less conspicuous part of the building prior to proceeding to ensure that the cleaning method has the desired effect and that it is not too aggressive as care needs to be taken to ensure that it does not cause damage. The building owner should be presented with the opportunity to inspect the cleaning samples so that they are aware of the likely results that the cleaning will achieve prior to proceeding with the work.
Also, prior to the commencement of the cleaning work, all air grilles, apertures, gaps etc. should be sealed in order to prevent the ingress of water or other cleaning materials into the building as this could cause damage to internal furnishings and finishes for which repairing liability could arise.
As part of a building external refurbishment project, masonry cleaning should be carried out first prior to any masonry repairs being undertaken as the cleaning process may dislodge loose sections of pointing etc. that will require replacement.
Stubborn staining to stonework in localized areas can be removed using a chemical paste poultice that is applied for a period of 24 to 48 hours. However, the level of success will depend upon how deeply engrained the staining is in the stonework.
The downside to masonry cleaning tends to be the expense as, depending on the size of the building, it can cost thousands of pounds. The building owner will therefore need to decide whether the benefits of having a clean, well maintained building outweigh the capital expenditure cost.
