All products leaving our works are packed in a manner to ensure safe delivery to site. This entails protection by CFC free polystyrene strips, shrink-wrapping and delivery on suitably sized pallets, frames or crates. These normally contain a maximum of 1 tonne for safe handling on site. It should be noted that it is the customers' responsibility to ensure safe unloading of delivery vehicles.
A suitable storage area will need to be set aside for the stone, which should be stored on firm, level surfaces and, to avoid contamination, should be sited away from wet or muddy areas. Storage should be as near as practical to the areas of working in order to minimise handling, damage and waste. Pallets should not be stacked on top of each other. Should it be necessary to store the material on site for any length of time, it should be protected from the elements and the environment.
The designer will need to be aware of the manual handling regulations and ensure appropriate lifting equipment is available to move and fix the heavy stones.
Ideally the best method of achieving satisfactory finished work, free from unsightly staining, mortar accretions and smearing, is prevention and good workmanship from an experienced Portland Stone Fixing Contractor. On facing work, it is also advisable to keep finished areas of walling covered as the contract proceeds to avoid splashing and staining from other works.
Where cleaning is required due to staining by accident or poor design, it is recommended that specialised cleaning materials are used. Such materials are manufactured by companies such as Tensid, whose addresses and contact details are listed in the Reference Section of the Manual. It should be noted that such manufacturer's recommendations and application methods should be sought for specific requirements.
Impact damage will occur from time to time in a building site environment. Where the damage is localised and small it may be appropriate to conduct an on-site repair using a lime mortar mix or even piecing in a small section of stone. In most instances a replacement stone will be required.
It is important to remember that Portland Stone does not normally require cleaning to safeguard its durability. Cleaning is purely a cosmetic requirement and therefore subject to personal interpretation. Many factors will have to be considered, including the orientation of the façade, the local microclimate and the prevailing current climatic conditions.
As an example, a damp warm summer, preceding a mild, wet winter and a north facing façade, could encourage the growth of algae, particularly in the first few years, as the mineral salts washed into the stone as part of the cutting process will provide nutrients on which the algae will feed. One client may accept that this is only a temporary phenomenon, whereas another may require the building to be cleaned and an algae controlling chemical applied. It is, therefore, important to consider the location and orientation of any building at the design stage. At the time of visits to the quarry to select stones, this consideration can be discussed.
Portland Stone should not be painted at any time.
All porous Limestones will draw in moisture from surrounding media. Therefore, for example contact with soils without protection could cause slight staining, particularly during the first two years and if the soils are heavily contaminated with mineral salts, accelerated weather could occur in certain circumstances. All buildings require annual inspections to establish the condition of both the exterior envelope and internal finishes. Although natural stone has a proven durability, without regular inspection the continuing integrity of the fabric may deteriorate and allow defects to occur
The following information is provided for the building owner to enable the planned regular maintenance of buildings from new. However, much of the work must be undertaken by specialist contractors.
Annual inspections should be carried out using suitable access equipment;
if this is not available, a binocular survey must be undertaken. The inspection should concentrate on the following:
If, as a result of this inspection, maintenance and/or repair is required, the following actions should be considered. It is important that the work is completed by experienced contractors using products suitable for Portland Stone. These products are available from companies such as Tensid, whose contact details are available in the Reference Section.
Any joints that have suffered from frost damage should be carefully raked out and repointed. Any jointing that has cracked and it is suspected that this is because of movement, should only be repointed after the cause has been established.
The continuing effectiveness of these joints should be checked. If, due to excessive movement, the joint is no longer effective, the cause of this should be investigated and any remedial action undertaken. If the jointing material has ceased to be effective, it should be replaced.
The most likely cause of decay in stone is by water. Careful attention must therefore be paid to identifying and, as appropriate, the rectification of any defective rainwater outlets, pipes or flashing. Particular attention needs to be paid to areas where water is allowed to pool then evaporate, leaving behind the dirt and the potentially damaging salts.
Bird fouling should be discouraged by the installation of anti-bird devices. The growth of algae and lichen can be limited where appropriate by the application of Biocides.
Rust staining and similar contamination caused by external ferrous items (e.g. signs and guard rails) should be investigated and the cause of the problem tackled.
Impact damage caused by external forces such as window cleaning equipment, vehicles etc, must be identified and rectified.
The Stone Federation is producing a guidance document on the Cleaning of Façades will be available at http://www.stone-federationgb.org.uk/Publications.aspx.
Frequency of Cleaning
All building materials require regular maintenance. The design of the building and its geological location will dictate the cleaning cycles required. The British Standard BS 8298 recommends cleaning every 5 to 10 years.
Buildings cleaned more regularly will benefit from not requiring more severe treatment by such techniques as grit blasting and chemicals. Atmospheric pollution, especially particulate emissions from diesel vehicle exhausts, will in time lead to the surface soiling of many building materials, both on new construction and older buildings recently cleaned.
External cleaning may coincide with other building component maintenance such as painting, when shared access will be available. Cleaning may involve the use of specialist plant and/or hazardous chemicals and must only be undertaken by an experienced specialist contractor.
A trial area should always be cleaned first. This area should be in a location that will not be seen in case the cleaning is unsatisfactory.
Graffiti is difficult to remove as it often penetrates the stone. Removal of this should be undertaken by a specialist contractor to ensure no long-term damage occurs to the stone. External areas, which are likely to be subjected to graffiti attack, may be treated by the application of sacrificial anti-graffiti coatings. These coatings are available from companies such as Tensid whose addresses and contact details are listed in the Reference Section of this Manual.
Creepers, such as Ivy, should be actively discouraged from growing as they will insert their roots deep into the masonry joints and cause long-term damage.
Nameplates and Other Fitments
When nameplates etc are regularly cleaned, care must be taken to avoid staining the surrounding stone. The use of a tightly fitting masking plate is recommended.