A Definitive Guide to Plaster and Render
Plaster and Render
Plastering is a process of covering rough surfaces with a plastic material to obtain an even, smooth, regular, clean and durable surface.
External plastering is termed as rendering which improves the resistance of the surface to rainwater penetration and other atmospheric influences.
Plasters for indoor use have to be abrasion resistant and suitable for decorating with any coating/tiles/wallpaper
Thickness can vary from 1mm -20mm depending on location and function
Usually, two or more coats are applied.
Types of Render/Plaster
Traditional form of render
Created by mixing cement, sand, water in suitable ratio /proportions
Used internally and externally mostly where water resistance surface is required.
Usually applied on rough surfaces like brick, stone, concrete surfaces
Available in a variety of colors – natural or pigmented
Ranges from smooth to textured
Economical and effective
Stronger and harder than lime render
Easy to apply
Extremely rigid and brittle – could crack or break easily
Not waterproof and have to be finished by applying paint
Recycling is hard/difficult.
Traditional form of render
Prepared by mixing sand and lime in equal proportions, cement sometimes added to improve strength
Flexible thereby reducing the risk of cracking
Leaves a traditional attractive finish
Less rigid and brittle than cement render
Eco-friendly and recyclable
Useful in ‘breathing wall’. It can store water and dry out easily
Requires expensive and skilled labor
More difficult to work than cement render
Takes more time to cure than cement render
Oldest and cheapest form of plaster
Commonly seen in rural areas and in structures of temporary character or low-cost housing
Made from earth mixed with chopping straw, hay or hemp with water in proportionate ratio
Do not provide resistant to rain
Poor resistance to erosion
Stucco plaster acts as a decorative feature and gives an excellent finish
Used for interior as well as exterior surfaces
Usually laid in three coats with thickness of 25mm
The first coat is called scratch coat, second a finer coat, also known as brown coat, and third is called the white coat or finishing coat
Made up of aggregates, binder, and water.
Alternative to traditional cement render
Added polymers to cement prevent cracking and help cement adhere better
Mostly suited for external surfaces and is weather-resistant
Applied on modern brick walls, lightweight cement blocks, insulation boards
Flexible and strong than cement binder
Less prone to cracking
Limited to a few background depending on polymer
Acrylic resin is added in mix during manufacture
Used as finished coat for previous renders
To get desired finish, aggregates are added.
More flexible and less prone to cracking
Not eco-friendly option.
Monocouch means a single layer
Provides protection from weather and acts as a decorative feature
Weather-resistant and breathable
Does not need painting
Not crack resistant.
LATH AND PLASTER ON TIMBER
Lathing may be either of wood or of expanded metal
Wooden lath is used for forming a ground for plastering timber partition walls and ceilings of timber floors
Laths are thin strips of well-seasoned wood fixed by nails in parallel to wooden frames
10mmm gap is provided between two successive strips for plaster
The plastering is then done in a usual manner.
Types of Finish
The finish is leveled and smooth surface
Mortar is made by mixing cement and fine sand in ratio of 1:3
Final coat/finish in which mortar contains big size aggregates which vary from 3-12mm
Waterproof, durable and resistant to cracking
Finish in which mortar which contains small pebbles or crushed stones
Waterproof, durable and resistant to cracking.
The final after being leveled is scraped with a straight edge, old saw blade or other tool
Various types of scrapped finishes are obtained by using different tools.
In this finish, ornamental patterns or textured surfaces are produced by working with various tools