What Happens if You Don’t PVA Before Plastering?

With plastering, preparation is everything. At Cuthberts of Edinburgh, we’re experienced plasterers who understand the importance of applying polyvinyl acetate before beginning the plastering process.

While it might seem like a minor detail, overlooking this step can have serious consequences, including weak finishes, cracking and even extra costs down the line.

In this article, we’ll explain what PVA is and why it is so important when plastering. Read on for more information…

What is PVA?

PVA stands for polyvinyl acetate and is a type of water-based adhesive that is instantly recognisable for its white glue. PVA isn’t used to glue things together itself, but it acts as a primer and bonding agent that prepares the wall for plaster. Builders mix PVA with water to create the primer that is then brushed or rolled on to the surface. Once it has dried, the wall is then in the perfect condition to accept the plaster.

Why is PVA used for plastering?

PVA serves a practical purpose when plastering, making the process easier and enhancing the durability of the surface.

It can help in a number of ways, including:

Bonding

PVA creates a slightly tacky layer on the surface, which gives the plaster something to grip onto. This is especially important on smooth or painted surfaces where the fresh plaster might struggle to stick. Without the grip, plaster can detach or fall off.

Priming

Many surfaces, especially bare brick or old plaster, are porous. These surfaces can absorb moisture extremely quickly and cause uneven drying. Using PVA seals these pores so that moisture stays in the plaster long enough for it to set.

Moisture control

If plaster dries too quickly, it can shrink and crack. PVA helps to slow down and control the drying process, ensuring the plaster gives you time to properly work on it and ensure a stronger finish.

What happens if you don’t PVA before plastering?

If you skip the PVA step when plastering, it can lead to a whole host of problems. This includes:

• Poor adhesion: Without a proper bonding surface, the plaster might not stick to the wall properly. This can lead to weal spots or sections of plaster falling off.
• Rapid moisture absorption: Porous walls can suck moisture out of the plaster too quickly. This means the plaster will dry before it is ready, making smooth application difficult.
• Uneven finish: When plaster dries at different rates across a wall, it becomes harder to level and make smooth. This can cause ripples and lumps in the texture.
• Cracking: Fast or uneven drying plaster can crack as it cures.
• Flaking and weakness: Finished plaster can fall from the wall or chip easily when it has not bonded properly.

How to apply PVA when plastering

Applying PVA isn’t complicated, but it needs to be done the right way. Here’s a step-by-step guide on how to apply it effectively:

1. Choose the right kind of PVA: Not all PVA is the same. Most plasterers use diluted PVA products, as they help prime the surface without creating a heavy film.
2. Prepare the surface: Before applying the PVA, you need to make sure the surface is clean and well prepared. Remove loose dust, dirt and any debris that is on the surface. Ensure the wall is dry and free from grease. If you are plastering on bare brickwork, it is worth quickly wiping it down to ensure the PVA can soak in properly. Preparing the surface properly will make sure the PVA bonds effectively.
3. Apply the first coat: Use a roller brush to apply your PVA evenly across the wall. This coat will seal into the surface and help regulate how much moisture the plaster will lose. Make sure the first coat has dried completely before moving on.
4. Apply a second coat: Once the first coat is dry, it will usually need a second coat. Apply it to the surface in the same way as the first coat.
5. Let it dry before plastering: After the second coat has dried, the PVA will become tacky. This is the best texture to apply the plaster. Once the PVA has become tacky, it means the plaster will grip better, and this is the pointat which you can start plastering.

Proper preparation makes all the difference when it comes to plastering a surface successfully. This includes applying PVA. If you want a professional plaster finish that stands the test of time, Cuthberts of Edinburgh is here to help. Get in touch with our expert team today to find out more.