Most house walls are finished with plaster, but over time, plaster can develop cracks which usually due to the movement of the property. These small cracks may get worse and even become a problem if left on their own.
With plastering services, clients should be given the option to repair or to have a new two coat finish system applied to their walls(plastering) and advised what is the best option to take. From knocks, holes, blown plaster, water damaged ceilings to plastering a room or house. Measurements are crucial to working out how much materials is needed and cost of labour.
In the picture to left the previous laths plaster had come away from the laths (it is also known as Blown). A usual indication of this is when tapping the wall or walls, a hollow sound is heard and a slight bounce to the touch. The remedy to fix this is to remove all of the blown areas and then apply restoration plaster (Thistle Hardwall or Limelite Renovating plaster) or apply plasterboards and then skim.
Depending on the depth of the previous plaster after fitting a plasterboard or boards a coat of Thistle Hardwall or Bonding (preferably Thistle Bonding for it's adhesive properties). This will be applied to level the surface, if need be, allowing it to be flat when skimming.
After being skimmed or plastered the text book recommendation before decorating is 3 to 4 week drying time but this is not always the case depending on the ventilation and warmth of the area that was plastered this may vary from 3 to 10 days.
Occasionally properties encounter accidents such as a foot through the ceiling when works are being carried out above or when the ceiling starts to come away from joists (timber) or lathes which over time begins to bowl.
In some cases the ceiling can fall due to how much it has blown or come away from its surface and in other case due to the amount of damaged caused by the water, which can be seen in the pictures to the right. First, source the cause of the water and have it repaired before any plastering work is done.
All the areas damaged should be removed that includes insulation if installed. Then the area should be prepared, re-boarded, prepared once more and skimmed. Enough time should be given to allow the plaster to dry before painting. According to the text book it takes plaster 3-4 weeks to be completely dry. But according experience it varies from 3-14 days. And of cause the weather which affects the temperature and how well the area is ventilated for the moisture to escape.
Rendering is when sand and cement is mixed to together with lime but today additives such as Sika, Renderguard Gold are more often used than Lime. The additives usually contain plasticiser, waterproofing and retarder. The additives help with application of the render and in forming a flexible mix that is applied to exterior of the property in most cases but is also used for the interior of the property when treating damp or onto external facing and non cavity walls that are subject to weathering on the exterior of the property.
The general ratio when mixing up render for exterior use is usually 4 parts sand and 1 part Cement (4:1) with an additive solution or 4 parts Sand 1 part sand 1 part Lime (4:1:1). The ratios determine the strength of the mix. if done incorrectly the mix will either crumble away or become very brittle and prone to cracking. When applying a two coat system the area should be applied first being a scratch coat or base coat which acts as a surface key for the second coat to hold onto. The second coat is known as a finish coat. This is where more attention to detail give as this the decorative finish.
Today's newest form of rendering is silicone base render which is more resistant to cracking, weathering and more breathable and it is also applied thinner than your regular cement render.
Plastering is a a building material that is manufactured as dry powder which is mixed with water to form creamy paste that is applied to walls and ceilings as decorative coating and can be used as a protective substance when used alongside Thistle hardwall, Thistle bonding or Cement Render known also as Float and Set. Using the right tools (plastering trowels, speedskims straightedge etc) when plastering the end result should be a smooth finish to the touch which minimizes the workload when decorating.
A two coat system should always be applied which allows for a good finish when done correctly. the first coat is used as a backing and the second to fill in any low points as well as to finish.
When painting newly plastered walls or ceilings a base paint should be used (Dulux Base Coat or Leyland matt emulsion watered down at a 50-50 mix). But before any painting the plaster should be allowed to dry. According to the text books it can take up 3-4 weeks for the plaster to dry, however this is not always the case. Depending on what the plaster is being applied to and the size of the area the drying time can and vary from 3 to 14 days. There are certain contributing factors that help with the drying time, like good ventilation and warmth. Temperatures of 10-15 degrees is ideal for the plaster to dry and high temperatures and to much air directly onto the plaster will cause it to crack.