The difference between plaster and render
Render and Plaster are different mortar based coatings that cover block Work. In a nutshell the coatings that are applied on the inside walls of a house are called plaster and on external walls called render.
The difference between the two is the consistency of the mortar applied to the wall. Render contains more cement than plaster due to the fact, being on the outside of your house, it needs to be water resistant (for obvious reasons). Some walls will need to be rendered due to the material used. For example landcrete and mud blocks expand and crumble if exposed to water over a long period of time. When rendering external walls it is also important to use a richer mix on walls that face the heavier weather conditions.
The purpose of plaster is to ensure you have a nice tidy finish, interior walls can be cleaned and easily decorated.
Both plaster and Render consists of cement, sand and water. It is best to use coarse sands for render although this will make the render harder to work with.
How to Lime Render a Wall
As mentioned above render is a great way to protect a wall from the elements. They work by absorbing water allowing it to be evaporated before damaging the wall. Learning how to render a wall can be a useful tool to have even if it just to make sure when you have work completed the contractors are doing it correctly.
Step 1- Preparation
Firstly you will need to prepare the wall for rendering, how you do this will be dependent on the state of the wall. If it has previously been rendered then start by raking or sawing off as much old render as possible. Once all of the old render is removed wet the wall with a garden hose to help attach the first layer of render.
Step 2 – Mix the Render
Mix 1 part lime to 3 parts sand in a large bucket, masonry sand is the ideal choice as its sharp with angular grains. Cement can be substituted for a portion of the lime which will increase the strength but reduce how breathable the wall is.
Step 3 – Apply the scratch coat of render to the wall
Several layers of render will provide the most effective protection for your wall. The first applied layer is called the scratch coat. Ensure this layer is applied to the wall with enough force for it to key into the wall, using a trowel is usually the best method for this.
Step 4 – Scratch the first coat of render to prepare it for a second coat
Before the first coat sets scratch the surface to provide a key for the second coat. Note that what you are doing is providing an easier gripping surface just as the wall provided with the first coat. Without scratching the render before each coat the render will not stick. The scratched surface can easily be applied with the edge of a trowel.
Step 5 – Apply the second coat of render to the wall
When the first coat has set most of the way apply more water and apply the second coat of render. If you require a third coat then repeat the process of scratching before it is applied. When finished allow the wall the dry slowly and the wall is finished.
For advice and guidance on rendering in Plymouth and the surrounding areas contact us today for a no obligation quote.