Preparing a Plaster Wall to Paint It


    – Step 1: Make a diagnosis to prepare the plaster wall

    – Step 2: Fill essential holes in the plaster wall

    – Step 3: Fill cracks and minor holes

    – Step 4: Sand and clean the plaster wall

    – Step 5: Paint the plaster wall

The installation of a wall covering, especially painting, requires preparing the plaster wall solid and smooth.

Gypsum walls can be brittle or damp and may have cracks and holes of varying sizes that need to be cleaned and filled.

To prepare a plaster wall, make a diagnosis of the wall to identify and correct defects. Finally, sand and wash the wall.

Materials for preparing a plaster wall

Filler coating

Approximately $7 for 5 kg 

Spatula (knife)

Starting at $3

Gypsum Tiles

Starting at $4

Circular sander

Starting at $30

Adhesion primer

Starting at $21 per litre 


Starting at $5


Starting at $4

Triangular scraper

$5 approximately 


Starting at $8


Starting at $2

Smoothing plaster

$5 for 1 kg 

Quackgrass brush

Approximately $5

Coating knife

Starting at $3

1. Make a diagnosis to prepare the plaster wall

Before painting a plaster wall, the first thing to do is make a diagnosis to verify its solidity.

Locate holes and cracks in the wall, as well as traces of moisture.

What to do if there is moisture on the plaster wall?

How do you know if a plaster wall is damp? Traces of moisture are visible on the wall: moisture leaves stains. You can also check with your bare hands: you can feel the humidity. There are also devices to measure the moisture of the walls.

Note: it is best to call in a professional who will determine the cause of the moisture in the walls. He will advise you on how to treat the moisture effectively.

If the plaster wall is brittle

If the plaster is floury or friable, you need to apply a primer for brittle substrates. The primer is used with a roller to the walls and allows you to harden powdery, floury or friable plaster supports.

To apply the primer on plaster walls :

    – Ventilate the room and protect the floor with plastic sheeting or newspaper.

    – Wear protective gloves and goggles.

    – Apply the product with a roller and allow to dry for the time indicated on the package.

2. Fill large holes in the plaster wall. 3.

If the wall has a large hole, fill it with plaster and plaster.

    – Remove debris and then scrape the hole’s edges with a triangular scraper to remove all brittle parts. This will ensure better setting of the plaster or patch.

    – Dust the spot with a quackgrass brush.

    – Prepare the plaster in a basin or plaster trough according to the manufacturer’s instructions.

    – Protect the floor covering with a tarpaulin or used sheets.

    – Wet the inside of the hole with a damp sponge to ensure good adhesion of the plaster.

    – Remove a small amount of sealer with a painting knife and place it in the hole.

    – Press the blade of the knife to push the coating inside the hole.

    – Smooth over the knife blade several times and remove the excess layer.

    – Allow drying before sanding lightly if necessary.

If there are cracks in the plaster wall

It will have to be covered with plasterboard to prepare a plaster wall with numerous or large cracks.

Interlining a wall consists of covering it with glass cloth. This is a resistant wall covering that allows you to consolidate the wall and mask its defects; you can then paint the glass cloth. There are glass cloths with different patterns.

In case of essential flatness defects of the wall

To prepare a plaster wall with many irregularities or unevenness, apply a smoothing plaster.

The smoothing plaster is applied over the entire surface of the wall.

    – Divide the wall into squares of about 50 cm side; you will gradually cover these squares with plaster.

    – Apply the plaster from the bottom of the wall.

    – Smooth with a plastering knife.

    – Allow drying before sanding lightly if necessary.

Note: it is possible to apply a smoothing plaster on glass cloth. In case your walls have cracks and unevenness, use the glass cloth and then apply the smoothing coat.

3. Fill cracks and small holes.

You can fill the small holes and small cracks with a filler or ready-to-use adhesive mortar.

    – Widen holes and cracks with a spatula.

    – Clean dust and plaster debris with a quack brush.

    – Fill the gaps with filler mortar with a spatula.

    – Remove excess plaster and smooth with the spatula.

    – Allow drying.

4. Sand and clean the plaster wall.

Wear a mask and goggles, ventilate the room you are sanding.

It is essential to prepare the plaster wall by sanding it, you eliminate roughness and obtain a perfectly smooth surface.

Sand the wall with an eccentric sander or a giraffe sander.

    – Equip the sander with heavy grit paper and sand the plaster wall once.

    – Then sand with fine-grit paper to completely smooth the surface.

    – Finish by dusting the wall with a brush before washing it with a damp sponge. Rinse the sponge regularly.

Important: Never use detergent to clean a plaster wall. You will have difficulty rinsing it and the paint you apply afterwards will not hold.

5. Paint the plaster wall

When you have finished preparing the plaster wall, paint it with a roller and a paintbrush.

    – Paint the perimeter of the wall with the paintbrush.

    – Paint the rest of the wall with the roller.

    – Paint the baseboards and window openings with a brush.

Hope the above helps you out. Remember to share your comments below.

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