06/04/2021 by Paul Atkins Plastering 0 Comments
Plastering 101: All About Plaster Types and Finishes
An innovative mixture of cement, gypsum, sand, and water, plaster is used for various applications. It comes as no surprise why we see plaster everywhere in the UK. But what makes plaster such a popular construction material?
We’re all familiar with it being a widely used construction material, but did you know there are different types of plaster and plaster finishes? Whether you are renovating your house or building your dream home, you should know the various types of plaster and plaster finishes and also how to go about the procedure of plastering surfaces.
We’ll cover all there is to know about plaster in this post. Continue reading.
Plaster: What Is It?
Here’s a fun fact for you: plaster has been around for ages, dating back to around 7500 BC. Several civilizations used it, including the people of ‘Ain Ghazal in Jordan and the Egyptians. The earliest type was lime mixed with unheated crushed limestone and used for covering hearths, walls, and floors in houses.
Plaster has now become a popular term not only among professionals in the construction industry but also among homeowners. When one hears the word plaster, the first things that come to mind are lots of dirt, mortar, trowel, and levelling bar. Whether it be lime cement base or clay filler, plaster is basically anything that can be put on the wall. It is a building material used to coat and protect internal walls and ceilings, and sometimes outdoor walls.
What Are the Different Types of Plaster?
As we mentioned above, there are various types of plasters available. They are used for different purposes. In this section, we will provide a detailed outline of each type.
1. Undercoat Plaster
The first type are undercoats. Before we go in depth, picture this first: an artist wants to paint a masterpiece. What tools does he need? What steps should he take first? Generally, artists will secure the canvas on which they will paint.
An undercoat is basically a canvas on which you can create some designs for your walls, ceilings, and other surfaces. As it is the base on which everything else is built, the mixing and application of undercoat plaster should be done right. Mixing it isn’t so tricky with the help of the right mixing drill.
Also, you want to make sure you’re getting the right consistency. Ideally, it is better to mix several batches before settling on the one you want. You also should section the surface you are working on and start applying the undercoat from there. This is to make sure it is evenly applied.
Here are different undercoat plasters you can use:
This type is used as a base for paint. An undercoat plaster, it is commonly used for decorative endeavours. It is also very useful in construction and can be used to build up walls. Most builders agree that browning plaster is most useful with more absorbent surfaces and recommend applying it at 11mm thickness for walls and about 8mm thickness for ceilings.
The drying time for this plaster type depends on the weather and the season. But generally, experts will leave it for a day or so before coming back to work on it. It’s worth noting that before anything else is done to the walls, a finish coat should be added first.
Bonding plaster is considered as an undercoat on which other things are added, much like browning plaster. That said, it is also the first coat to be applied to a newly patched all. Like browning plaster, it is applied at 11mm for walls and 8mm for ceilings. When it is levelled off, builders mark it with a nail to provide a key for the topcoat to follow.
Due to its versatility, it is very popular in building construction and used on all sorts of surfaces including concrete and even engineering blocks. It is an ideal wall plaster as it is not dependent on the absorption levels of a surface to be effective.
This undercoat plaster is widely used with masonry backgrounds such as medium-density blocks and bricks. Like with the other undercoat plaster we have mentioned, hardwall plaster is also an ideal base to work with. What makes it so popular is that it is also very easy to apply.
The caveat, however, is that hardwall plaster should be used only on structures in good condition. This is because crumbling walls could cause it to crack.
Tough Coat Plaster
Finally, we have the tough coat plaster. As its name suggests, it is very tough and can take on conditions that the two previously mentioned plasters just can’t handle. Tough coat plaster provides some protection from fire and is a great base for masonry backgrounds. It also possesses high impact strength. While it isn’t best used on frozen walls, it can still do a good job.
2. Topcoat Plaster
The second type are topcoats. So, if an undercoat plaster is the canvas that you draw on, a topcoat plaster is the painting itself. As its name implies, topcoat plaster is the final layer of coating you apply before you paint your walls and other surfaces. As such, its mix is usually smoother than an undercoat plaster.
Topcoat plasters also contain more water than others. In a three-coat system, the finish coat (otherwise known as the topcoat) goes on after the scratch and undercoat. Topcoat plasters should be mixed properly so as not to affect the smoothness of the surface you are working on.
Unlike undercoats, it is preferable to mix topcoats manually than use mechanical mixing drills. Take note that topcoats dry up faster than undercoats and once they have dried up, they can’t be used anymore. It would be such a waste to have to throw them away, so be sure to mix them properly.
The three most common topcoats are carlite, thistle, and dri-coat plaster.
This topcoat is usually used on top of a background. What makes carlite plaster so versatile is that it can be used on a variety of surfaces and added as decorative finishes. While other topcoats like thistle plaster take three hours to set, the setting time for carlite plaster is just an hour and a half.
When it comes to durability, carlite does a pretty decent job. It also has high-impact strength and is scratch-resistant, making it a durable base for the application of decorative finishes. If you want a plaster that provides a smooth and high-quality surface for internal walls and ceilings, you can go for this type.
Next we have thistle plaster, one of the most popular types of finish plasters and usually comes up at the end of the plastering process. Just like carlite plaster, thistle plaster is also very versatile and convenient to use. For this reason, most builders prefer thistle over other types for small repair jobs and other tasks that require plaster.
You can use this topcoat on plasterboard or as part of a two-coat system. Another quality that adds to its appeal is that it can easily be applied by hand or with a mechanical tool. What’s more, thistle plaster provides a smooth surface on which you can apply various decorative finishes.
This topcoat is a little different from the others as it is often used for re-plastering after installation of a new damp-proof course, not so much for decorative application. Dri-coat has a strong reputation of preventing the movement of hygroscopic salts from the background to the surface. Take note that hygroscopic salts tend to absorb atmospheric moisture. If damp walls are a problem for you, then dri-coat may prove helpful in protecting your walls and keeping them in pristine condition.
However, dri-coat is not recommended on frozen backgrounds because they affect its efficiency. Dri-coat is also not effective in reducing the spread of fire, which is why it is recommended that this plaster should not be exposed to extreme temperatures.
3. Other Types
So far, the plasters we have mentioned fall broadly into two categories: undercoats and topcoats. But there is also another plaster that can act as both an undercoat and a topcoat: one coat plaster. It is a very popular plaster variant as it consists of the traditional gypsum material and possesses a thicker consistency. This plaster can work well with thicker layers than other variants, making it the go-to plaster for repair jobs.
Applying it can be done in just a few steps. A scratch coat is not really required, which means you don’t have to mix several batches to get the right consistency. You can apply one coat plaster by hand or with the help of mechanical tools to get a smooth finish over small areas.
What Are the Different Types of Plaster Finishes?
This time, let’s go over the common types of plaster finishing:
⦁ Smooth cast
⦁ Rough cast
⦁ Textured finish
⦁ Scrapped finish
⦁ Pebble dash
As its name suggests, it refers to a finish that presents a levelled and smooth surface. To get a smooth cast, the mortar for finish should be a mix of cement and fine sand in a 1:3 ratio.
The exact opposite of a smooth cast, this finish contains a proportion of fairly big-sized coarse aggregates. The mortar for the final coat is a mix of cement, find sand, and coarse aggregate in a 1: ½: 3 ratio.
For this finish, you have to work with various tools in the freshly applied final coat to produce ornamental patterns or textured surface.
To get a scrapped finish, the final coat should be 6 to 12 mm thick as 3mm is removed in the scrapping process. When the final coat has already been levelled and allowed to stiffen for a few hours, it is scrapped with a steel straight-edge blade or other similar tool. This is to remove the surface skin of the mortar.
It’s worth mentioning that the scrapping should be done after the setting has taken place. Of the finishes we have mentioned so far, this type is the least liable to crack. If that is what you are after, then go for this type of finish.
This type of finish is achieved by crushing small pebbles or stones of suitable size (10-20mm) and throwing them onto a freshly applied final coat of mortar and left exposed. The stones have to be wet when thrown onto the final coat.
For a pebble dash finish, the mortar for the final coat should be a mix of coarse sand and cement in a 1:3 ratio. A pebble dash finish has the same advantages as that of a rough cast and scrapped finish.
How Can Plaster Improve a Property?
Whether you are keeping the long-term resale value of your home or trying to sell it, a remodel should be on your priority list. A few updates and changes can significantly increase your property’s market value. One great way of adding value to your property is by adding plaster to your walls, ceilings, and other surfaces.
Here are some of the many ways plaster can improve your property.
There is no doubt that plaster is among the most durable materials out there. It can last for centuries when properly installed. What’s more, it can withstand wear and tear and is fire-resistant. By using plaster, you can increase the durability of your home. This ultimately increases the market value of your property.
Add Details to Increase Aesthetic Value
If you are thinking of adding a bit of style and charm to your property, know that plaster is the perfect to material for that. You can use plaster to add little details to a fireplace, crown moulding, and decorative vent.
As we have mentioned many times now, plaster is so versatile and can be moulded into any design or shape you want. With the help of a professional, you can craft these details to your home and increase its aesthetic value.
Improve Curb Appeal
Since plaster can also be used outside, you can use it on your outside walls. It merits repeating that plaster is a highly durable material that can withstand all weather type. You can use plaster to create architectural detailing outdoors and expect it to last a long time.
Improve Your Property with Plaster!
Engage a plasterer today to get your plastering job done. Turn to Paul Atkins Plastering. With over 20 years of industry experience, there is no job that is too big or small for us.