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Plastering a Concrete Block Wall

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Learn how to plaster up an aerated concrete block wall

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Plastering for the first time? Help is at hand! This specially designed video will take you through everything you need to know when you plaster an aerated concrete wall.


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annieduncan - Sikana
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In this video, we are going to learn how to plaster over an aerated concrete wall.

There are numerous advantages to having an aerated concrete wall: it is light, easy to put together, it has very effective thermal insulating properties and is nonflammable. Filling in the gaps in the plaster will allow you to level out your wall's surface and to block up any small holes so that it is ready to be painted or decorated.

This is a long activity that will take a day to complete since you will need to allow sufficient drying time between the application of each layer

To carry out this work, you will need: a bucket, a spatula, two (japanese) putty knives, a broom and some plaster gap filler mix

There are two stages to applying the plaster gap filler which we will outline to you in detail

STAGE 1: Applying the first layer of plaster filler

To begin, scrape the wall with a spatula to remove any roughness. To apply more force, place the spatula in the palm of your hand and place your index and middle fingers on the opposite face of the spatula. Scrape the entire wall surface with sideways movements from left to right, and from top to bottom.

Prepare the plaster filler by mixing the powder mix and water together. Follow the product instructions to measure out the correct proportions of water and plaster powder. Pour the correct dose of water into the bucket and then pour in the powder and mix it until your plaster has an even consistency.

The plaster is properly mixed when it sticks onto the spatula. If it doesn't stick to the spatula, it is too wet. If, on the other hand, it is too difficult to mix, there is not enough water. This plaster dries fairly quickly, generally in 30 to 40 minutes, so it is better to work with small quantities.

Before remixing the plaster, clean the bucket well so as to avoid small lumps of hardened plaster forming.

The first plaster filling layer is applied in horizontal strips, starting from the top and working downwards. Always work with two knives: the first one is for spreading the plaster and the second one is very useful for cleaning the excess plaster off the first knife.

Put a generous amount of plaster on the first knife and spread the plaster downwards in a vertical strip of measuring around 1 metre (3'2") Clean the knife, then repeat the same movement to remove the excess. If lines appear, it means that the plaster has been spread too thinly. If this happens, add another layer of plaster over the top.

On the other hand, if large strips of plaster appear, it means there is too much. In this instance, continue spreading the plaster to remove the excess. For the strip in the middle of the wall, spread the plaster from the bottom to the top. This will connect it perfectly to the plaster on the upper part of the wall. If you do the opposite, meaning spreading the plaster from top to bottom, there will be some irregularities at the point where to two strips of plaster meet.

When applying plaster to the corners, apply the plaster filler in horizontal strips from the wall edge, not in vertical movements. This technique will ensure none of the filler runs onto the adjacent wall.

Once the first layer has been applied to the entire wall, clean the tools and leave it to dry. This period can take anywhere from 2 hours to half a day, according to the plaster used and the surrounding temperature.

STAGE 2: Applying the second layer of plaster filler

When the first layer is dry, meaning it is white and dry to the touch, use a spatula to scrape off the rough bits of dry plaster. The first layer needs to be smooth.

Then sweep or vacuum up the debris carefully. The second layer is applied in horizontal strips from left to right for a right-handed person. This will correct the small grooves left over from the first layer.

Spread the filler over the wall with left to right movements, and scrape the plaster filler with right to left movements. Proceed in the same way for the entire wall surface and leave it to dry.

Once the second layer is dry, your preparation is finished.

Your wall can now be painted or have a decorative plaster applied to it. To learn how to apply decorative plaster, refer to our video called 'Applying decorative plaster on an aerated concrete wall.'


Next video

Sikana - How to Apply Decorative to Plaster a Wall
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