What is plastering?

Plastering is a term that is usually used to encompass the entire trade, but specifically it is the process of using coats of a paste made of an aggregate and binding matrix. It is used to create smooth surfaces and to finish walls.

Different types of plaster

There are different kinds of plaster available, each using a different binder in their mixture.

Lime plaster

Lime plaster is made using lime and water. It is good at allowing moisture to escape and evaporate, and even draws moisture out using capillary action.

Gypsum plaster

Created with water and calcium sulphate, gypsum plaster is fire resistant and durable. It doesn't shrink and has an efficient setting time.

Cement plaster

Created using cement, cement plaster is very durable. It is low cost and easy to use, and it is good at preventing the circulation of moisture.

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What is skimming?

Skimming, or applying a skim coat, is a specific plastering technique. It involves applying a singular thin coat of plaster to a wall to finish the wall. It is often used on existing plaster, as an existing plastered wall simply needs to have a smooth surface to allow for decoration. It can be done to materials like rough cement to make it smoother than it would be with sanding alone.

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Benefits to plastering

So if a skim coat can make a surface nice and smooth, what is the point in plastering? What are the benefits?

Insulation

Dry plastering can be used to create insulation on interior walls using plaster board in the plastering process. This can be great for reducing moisture and increasing warmth and sustainability in a home.

Stable and uniform

Plastering, as it uses a plastering method that involves a number of coats, creates a finishing plaster that is completely smooth and uniform. It is easy to reach this goal using a number of coats, regardless of what the surface beneath the plaster is like.

Pollution free

Plaster does not produce as much dust on its surface as other materials, meaning it is less polluting to a home.

Less likely to crack

Plastering is a robust and durable solution. The chemical reaction that occurs during the plastering job creates a very strong bond in the material that means it is not likely to crack and can actually help increase the structural integrity of the wall.

Versatile

Plaster can be finished in a huge range of ways. Different colours, textures and designs can be implemented into the final product to fit the building and desired aesthetic.

Benefits to skimming

What are the benefits of only using the thin coat in skimming?

Hiding imperfections

If you're looking to hide a few cracks or dimples in a surface, but you don't need to reap the other benefits of plastering, then a skim plaster coat will do just fine. It will make the surface smooth and hide anything untoward.

Adding strength

Just like plastering, skimming can help to increase the strength of a surface by preventing any cracks from developing.

Improving adhesion

The smooth surface created by a skim coat is perfect for painting or wallpapering over. The thin coating works well to help paint and glue to adhere to the wall, so that regardless of what is underneath, it can be properly decorated.

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Negatives to plastering

As with any process, there are some downsides to both plastering and skimming. For plastering, these are:

Cost

Hiring professional plasterers, or alternatively buying all of the equipment you need to do your own plastering can be pricey. The cost of doing a small room may mean that you can only afford to do one room at a time, which can slow the renovation process down.

Time

Plastering is not a quick process. It takes time as each layer has to be left to dry completely before the next layer is pasted on. As a result, it can be incredibly time consuming. This can be a problem when you're plastering a room in a property you live in, as the room may be unavailable for some time while the masonry work is done.

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Negatives to skimming

Likewise, there are certain negatives to skimming, too.

Difficult to achieve

Skimming relies on a very thin coat being created. It is not as easy as plastering, and one of the biggest points of difference between plastering and skimming is that the latter requires more skill to get it perfect. With plastering there is much more space to hide, whereas skim plastering only uses a single coat, so there is no room for error.

Not as smooth or uniform

Due to the above, a lot of times when a skim coat is done, it is not as uniform as a plastering job. It is incredibly difficult to get one single thin coat to look as uniform as the multiple layers of plaster.

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Other kinds of plastering

In addition to skimming, there are a number of types of plastering that you can look into, for example:

• wet plastering
• dry plastering
• rendering