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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

Cement 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

FINISH

Ranges from smooth to textured

PROS

Economical and effective

Stronger and harder than lime render

Easy to apply

CONS

Extremely rigid and brittle – could crack or break easily

Not waterproof and have to be finished by applying paint

Recycling is hard/difficult.

Lime Render

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

PROS

Less rigid and brittle than cement render

Durable

Eco-friendly and recyclable

Useful in ‘breathing wall’. It can store water and dry out easily

CONS

Requires expensive and skilled labor

More difficult to work than cement render

Takes more time to cure than cement render

Mud Plaster

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

PROS

Environment-friendly

Cost-effective

Easily repaired

CONS

Do not provide resistant to rain

Poor resistance to erosion

Stucco Plaster

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.

Modern Renders

Polymer Render

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

PROS

Weather-resistant

Flexible and strong than cement binder

Less prone to cracking

CONS

Limited to a few background depending on polymer

Not ecofriendly.

Acrylic Render

Acrylic resin is added in mix during manufacture

Used as finished coat for previous renders

To get desired finish, aggregates are added.

PROS

More flexible and less prone to cracking

Moisture resistant

CONS

Not breathable

Not eco-friendly option.

Monocouch Render

Monocouch means a single layer

Provides protection from weather and acts as a decorative feature

PROS

Weather-resistant and breathable

Does not need painting

CONS

Expensive

Not crack resistant.

Other Types

SILICON RENDER

WATERPROOF PLASTER

COMPOSITE PLASTER

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

Smooth Cast

The finish is leveled and smooth surface

Mortar is made by mixing cement and fine sand in ratio of 1:3

Rough Cast

Final coat/finish in which mortar contains big size aggregates which vary from 3-12mm

Waterproof, durable and resistant to cracking

Pebble Dash

Finish in which mortar which contains small pebbles or crushed stones

Waterproof, durable and resistant to cracking.

Scrapped Finish

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.

Textured Finish

In this finish, ornamental patterns or textured surfaces are produced by working with various tools

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