Plastering is one of the most important tasks done in almost every construction. It protects the interior/exterior surface as well as improves the aesthetics of a structure. In this article, we will discuss different types of plaster finishes used in construction.
What Is Plaster?
Plastering is a process of covering the rough surfaces of various elements like columns, beams, walls, ceiling, etc with a thin coat of a type of plastic material or plastic mortars to form a smooth and durable surface. The plastic material used for plastering is known as plaster.
Plaster is a mortar consisting of ingredients like cement, sand, and water respectively. Plastering can be done on the internal surfaces as well as on the external surfaces of elements. Plastering done on external exposed surfaces is termed rendering.
Purpose Of Plastering:
Plastering is mainly done for the following purposes:
- To protect the external surface of the structure from harmful atmospheric effects such as rain, sun, wind, snow, etc.
- To give a smooth finish to the rough elements of structures.
- To give a decorative effect to the surface and improve its appearance.
- To protect the surface from vermin.
- To hide or inferior materials defective workmanship.
There are various types of plaster finishes that are selected depending upon a few factors like:
- Easy availability of materials.
- Type of structure.
- Requirements of durability.
- Requirements of quality and strength.
- Requirements of types of finishes.
- Availability of sufficient funds.
Based on the various factors stated above, the types of plaster and the types of plaster finishes are chosen for a given structure. Also, another factor affecting the selection of the types of plaster and plaster finishes is the cost.
The plaster selected for a structure should cost to an optimum amount or else the estimated cost of the structure may give a heavy variation.
Here we study different types of plaster finishes briefly.
Types Of Plaster Finishes
Finishing is generally done to provide a smooth finish to a rough surface and to give a decorative look to a surface or you can say that to make a surface look aesthetically beautiful.
Different types of plaster finishes are listed below:
- Smooth cast finish
- Sand faced finish
- Rough cast finish or spatter dash finish
- Pebble dash or dry dash finish
- Depeter finish
- Scrapped finished, and
- Textured finish
Let us learn about each type of plaster finish in detail below.
1. Smooth Cast Finish
In smooth cast finish, a completely smooth and levelled surface is acquired. The mortar prepared for the smooth cast finish is made of cement and fine sand, which are mixed in the ratio of 1 part cement and 3 parts of fine sand. Water is added according to the required quantity.
The prepared mortar is applied using the wooden float. Steel floats are generally avoided for applying the plaster on external surfaces because the steel float gives a super smooth surface, which may develop cracks under exposure to atmospheric conditions.
2. Sand Faced Finish
Sand faced finish is obtained when the plastering is done in two coats. The ingredients are the same as the mortar prepared for smooth cast finish. The ratio of cement and sand for the first coat 1:4. The thickness of the first coat is 12mm.
The first coat is provided with zigzag lines. It is because a smooth surface won’t hold a freshly applied coat of mortar. The first coat is cured for 7 days with water.
Then after the second coat of 8mm thickness is applied. The ratio of cement sand mix mortar for the second coat is taken as 1:1 respectively.
The final coat is then finished with clean and washed sand of uniform size, by rubbing it on the plaster surface. This process results in having sand particles on the surface of plaster.
3. Rough Cast Finish Or Spatter Dash Finish
It is a type of plaster finish in which the mortar consists of coarse aggregates too with the regular plaster mortar ingredients. The mortar, here, consists of cement, sand, and coarse aggregates in the ratio of 1:1.5:3, respectively.
The mortar is dashed against the plastered surface using is a large trowel. Then the surface is roughly finished by the means of a wooden float.
This type of finish is commonly used for external renderings. Rough cast finish is waterproof, durable and a crack-resistant type of finish.
4. Pebble Dash Finish or Dry Dash Finish
The final coat of pebble dash finish or dry dash finishes a thickness of 12mm. The mortar is same as the mortar used for smooth cast finish, in the ratio 1:3.
Pebbles of size 10mm to 20mm are dashed against the surface of fresh plaster. The pebbles are lightly pressed into the mortar using a wooden float. This type of Plaster finish normally used for decorative purposes.
5. Depeter Finish
Depeter finish is similar to the pebble dash finish. A 12mm coat is applied & while the plaster is still wet, small pieces of gravel or flint are pressed with a hand on the surface of the plaster.
To obtained different and beautiful patterns, flints of various colors are used like the pebble dash finish, depeter finish is also a decorative type of plaster finish.
6. Scrapped Finish
The thickness coat of scrapped finish varies from 6mm to 12mm. After the coat is stiffened, the surface is scrapped in different patterns, which are 3mm deep.
Different tools such as steel straight edges or old saw blades are used for scrapping the plastered surface. Scrapped surfaces are usually less liable to cracks.
7. Textured Finish
Textured finishes are generally used with stucco plastering. Different textures, as well as various ornamental patterns, are created on the surface of plaster. The textures and patterns are created using some special tools and also skilled workers are required for that.
So, these were different types of plaster finishes that are widely used. Which plaster finishes do you like most? Let us know in the comments below.