Regardless of how much care is taken during construction, a final wash down will most probably be required prior to handover of the building.
All cleaning should be carried out in accordance with BS 8221-1:2012 Code of practice for cleaning and surface repair of buildings. Cleaning of natural stones, brick, terracotta and concrete.
The following notes are offered for guidance only. Whatever method of cleaning is chosen it should be trialled on either an unfixed stone or a part of the finished structure that is hidden. This will determine whether the desired affect can be achieved without detriment to the finished product.
Dry clean using either a stiff bristle or fibreglass brush to remove light deposits such as mortar. Do not use any metallic or wire brushes as this will permanently mark the face of the cast stone units.
Power washing is not recommended, as this could damage the fine surface of the cast stone units or the mortar joints.
Some dirt is water soluble and water washing is a very simple process. It can be undertaken by bucket and brush, low pressure hosepipe (to no greater power than 1400 psi or 100 bar) and brush or low pressure multiple sprays and brush.
For more stubborn stains a mild detergent such as Sugar Soap can be added and then rinsed off.
It is extremely important to avoid high levels of saturation of the stone to avoid problems of over-wetting such as staining as dirty water dries out or efflorescence caused by mobilisation of soluble salts both in the stone and mortar joints.
This is one of the most popular methods for cleaning new cast stone but care must be taken to follow correct procedures.
Hydrochloric acid or one of a number of proprietary cleaners can be used to remove lime bloom, mortar stains and deposits. Hydrochloric acid should be diluted to 7– 10% and proprietary cleaners as per the manufacturers instructions. The stone and surrounding surfaces (particularly below the application area) should be wet with water prior to any acid cleaning to prevent surface burning.
Chemical cleaners can change both the colour and, to some degree, the texture of the stone. It is therefore recommended that as a minimum whole stones area treated and depending on the appearance after treatment, adjacent areas may require treatment to maintain uniformity of appearance.
Surface debris can be removed prior to cleaning with a plastic or wood scraper. Do not use metal implements as this can irreparably damage the surface.
Unusual stains such as grease or paint can be cleaned using the same procedures as recommended to clean concrete. However, this is a specialist area and advice should be sought from a specialist cleaning company prior to any work being carried out.
Always follow the cleaner manufacturers instructions and use experienced operatives for the cleaning process.
Some cleaning chemicals can be extremely dangerous therefore Health & Safety precautions must be strictly adhered to.
It should be noted that the best method of keeping cast stone clean is prevention. It is advisable to always protect cast stone during construction especially projecting surfaces such as copings and cills. Minimal time spent on damage prevention can save more time and money at the end of the project.
Advice offered by Amber Precast Ltd is given in good faith and it is to the best of our knowledge accurate and true, but is offered without guarantee.
If you require more information please contact us on:
tel: 01773 540707 email: firstname.lastname@example.org
Reference GN/007 JANUARY 2010