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Plastering an internal wall is a common method of providing a smooth finish, which can then be decorated. Plaster is supplied as a powder and when added to water forms a paste that can be put over internal and external walls.
Plaster dries soft allowing it to be shaped by metal tools and even sandpaper and as such is an ideal finishing material but is a poor load bearing material.
The current plaster on the market today is based around Gypsum. Gypsum is a mineral that is non-sustainable and has to be mined. Gypsum based plasters are also not very breathable and so can be vulnerable to mould in wet environments.
While Gypsum is prevalent in some countries such as the USA, Thailand, Germany, and Ireland, and in parts of the UK, it still requires transportation to factories that produce plaster, and then to the site. These road, ship and air miles add up the amount of carbon dioxide used to create plaster. Gypsum mining can also affect the local wildlife and old mine shafts can cause problems for years after closure.
Earthen based plaster consists primarily of clay. Clay is used as the binding material and can be bought straight from the clay pit to the site for onsite mixing reducing fuel miles used. Sand is then added to the mix to give it some structural strength.
Sand can either be acquired locally or from clay pits. Recycled construction aggregate can also be added at this stage to reduce the need for new materials.
Fibres are then added to give the mix tensile strength and to reinforce it. These fibres can take many forms, but often plant fibres such as dry straw or coconut fibre are used to keep the plaster natural.
The materials used in earthen plaster allow it to be less toxic and energy intensive than standard plaster. This makes it ideal for the green builder. Clay's natural breathing property of absorbing and diffusing water vapour and heat, helps balance changes in humidity and temperature keeping cool in summer and warm in winter. This makes it ideal for use in houses built with Passive Solar Design.
Clay also absorbs odours and is an effective sound insulator.
Clay does take longer to dry than traditional plaster with drying times as long as a week. This is an old technology reinvented so there may be difficulties in finding tradesmen with clay experience.
Lime based plaster was used on many buildings until the 1940s but some of its benefits have found it being used again particularly with other alternative materials.
Lime based plasters are known to be breathable which is useful in construction as it helps to control internal moisture levels.
Lime plaster has many of the same advantages of clay plaster. However once set it is not as reworkable as clay plaster, which when soaked with water can be remoulded. The lime required to make it has to be heated to 1,200 degrees Celsius, which is a very energy intensive production technique.
Whilst Gypsum mining may not be the most ecologically devastating activity in the world alternative plasters are much more eco-friendly and will also allow the house to be remodelled and changed as time goes on.
The enhanced breathability of both lime and clay plasters will reduce the load on ventilation systems and the higher thermal mass of clay will save a small amount of heating from being used.
Plasterboard - also called Wallboard
This is a sheet of gypsum between sheets of stiff paper. It is used everywhere in building and DIY, such as walls, ceilings, extensions, stud walls and stud partitions and timber framed buildings.
Plasterboard and wallboard can be supplied with a vapour barrier. This is a thin, metallic backing, like tinfoil. This type of plasteroard is used in timber-framed buildings and as a barrier where moisture might be around.
Specialised plasterboards are as follows (just some exaples):
Current 2007 estimates put the amount of plasterboard and wallboard waste from UK construction and demolition sites at around 900,000 tonnes per annum. This is a huge amount, and so last year a voluntary agreement was set up by the Gypsum Products Development Association (GPDA) which, in the UK, represents Knauf Drywall, British Gypsum and Lafarge Plasterboard. The UK's plasterboard recycling capacity is about 500,000 tonnes per annum.
WRAP (Waste & Resources Action Programme) works to encourage and enable businesses and consumers to be more efficient in their use of materials and recycle more. This helps to minimise landfill, reduce carbon emissions and improve our environment.
See WRAP for building materials recycling: WRAP at www.wrap.org.uk