Summary: Learn how to plaster interior masonry walls, apply the basecoat, score the basecoat and plaster an external corner.
Plastering is the traditional way of covering walls but it does require practice to master the techniques. Additionally, you do need to be reasonably fit, as it is quite strenuous work. Firstly, assess the job to decide whether it would be more cost effective to engage the services of a professional plasterer. As an alternative to plastering you may want to consider dry lining the walls.
There are several different types of plaster available. Professionals use a gypsum-based plaster that needs to be mixed correctly and dries quickly. If a novice, you would be better advised using a ready-mixed plaster.
Whichever plaster you decide to use, remember to wear goggles and a respiratory mask when mixing, as the dust can be harmful. Be careful not to contaminate the mixture with small pieces of debris during mixing as these make it difficult to apply to the walls and get a smooth finish. Do not mix too much plaster at once, especially if it is a hot day, as it will dry out too quickly.
You can plaster directly onto plasterboard stud walls or over a basecoat or undercoat that has been applied to masonry walls. This project is looking at plastering an interior masonry wall with a base coat and top coat.
For the smoothest finish on a masonry wall, you should apply a basecoat before the finishing plaster. There are various basecoats available to choose from, but all are applied in the same way. The easiest basecoat to apply is Undercoat Plaster, which is also the best insulator.
However, if you have damp walls, you should apply render (a sand and cement mixture), which is hardwearing and can be treated to increase damp-resistance. If your walls are very damp, such as in a basement, you might consider a cement-based waterproof membrane as a basecoat. Non-porous walls that have been sealed with a PVA solution can have a bonding plaster applied as an undercoat.
To maintain the correct depth of plaster, temporarily fix battens to the wall, 1m apart.
Hold the feather edge firmly against the battens to smooth the plaster and achieve the correct thickness.
When applying the basecoat plaster to the wall it must lie level with the point of the angle bead.
Use the edge of the plastering trowel to scrape away about 2mmof the basecoat near the angle bead to allow for the layer of finishing plaster.
Applying a finishing coat is known as skimming and should be carried out when the basecoat is still slightly damp. If the basecoat is drying out too fast, moisten it by splashing water over its surface.
Hold the hawk close to the wall and use a plastering trowel to transfer the plaster from the hawk to the top of the wall.
Let the face of the plastering trowel rest on the apex of the angle bead at external corners to maintain a professional finish.
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