Having the right thickness of render has a number of implications, not least for how a building looks and how it lasts. The correct thickness varies depending on the type of render you are using and what the walls are constructed from. Too thin, and it will crack or fail to keep water out. Too heavy, or it might fall off, or be too expensive.

Why Render Thickness Matters

There are a lot of things that render thickness impacts. It shields walls from rain and wind. It also makes buildings look good and can even help keep heat out or in. If you’ve used the wrong depth of render, you can have issues like:

• Cracks
• Water damage
• Render falling off
• Uneven finish

Variables That Influence Render Thickness

A few things impact how thick your render needs to be. These include:

• Type of Render: Some renders (such as acrylic) can be thinner than other types of render (such as cement).
• Wall Material: Bricks may require a different thickness than concrete blocks.
• Weather: If you live in a place that gets a lot of rain, you may want bulkier render.
• Desired Smoothness: Different smoothness levels may require different thicknesses.

Recommended Render Thickness

Cement Render

Cement render is strong and is great to protect walls. It’s typically going to be about 20-25mm thick. This enables it to adhere nicely and not easily crack. You may even have to apply it twice to make it that dark. The experienced team at Australian Rendering Company, providers of cement rendering in Melbourne for over thirty years, stress the significance of applying the correct method to achieve the right render thickness when it comes to getting a successful finish that will last. They can be reached on 0466 943 872 or contact@australianrenderingcompany.com.au.

Acrylic Render

Acrylic render is flexible compared with cement render. It can normally be worn thinner, in the realm of 1.5-2mm per coat (3-4mm in total). This makes it fine for walls that could shift slightly. It’s not bad at keeping water out, either.

Lime Render

Lime render is another kind of render. It’s good for old buildings because it allows walls to breathe. It should be roughly 15–20mm thick. You may have to apply a few thin coats to find the sweet spot.

Polymer Render

Polymer render uses silicone or another artificial material. They are good at water and cracking resistance. Typical thicknesses are in the range 15-20mm. For external walls where a weather shield is important, these are great.

How to Apply Render to the Right Thickness

1. Prepare the wall: Scrub the wall and ensure that it is rough enough for the render to adhere.
2. Mix the render: Read the bag to get instructions on how to best mix the render.
3. First coat: Apply the first coat of render with a trowel. Make sure it’s even.
4. Scratch the surface: When the first layer is somewhat dry, scratch it so that the second layer will adhere.
5. Apply the second coat: Apply the second coat and smooth it over.
6. Cure the render: Leave the render damp for a few days, so it dries out slowly, and doesn’t crack.

Tips for Achieving Good Render Thickness

• Check the thickness as you go with a gauge.
• Do not attempt to apply all render at once.
• Let each coat dry slightly before applying the next one.
• If in doubt, consult an expert.

Render Thickness and Wall Types

Also, the kind of wall that the render is going onto will affect the thickness.

Brick Walls

Brick is relatively porous and can accommodate quite a variation in render thickness. The ideal thickness for brick is 20-25mm with a cement render finish attached. The bricks should be pre-wetted for rendering.

Concrete Walls

Concrete walls prefer a coat of render that’s a bit thinner. Approximately 15-20mm thick is a good finish for a cement-based render over concrete. Thin acrylic renders at 3-4mm total are possible as good adhesion and flexibility are present on prepared cement-based substrates.

Hebel Walls

With Hebel, “Hebel-specific” render is necessary. These systems typically incorporate thin-bed adhesives and reinforced renders in order to match the special characteristics of the material. Hebel render is normally about 5-10mm thick, but you should always follow the manufacturer’s recommendations.

Blue Board

Blue Board requires a specific acrylic render system applied to fiber cement sheeting. These systems typically consist of a base coat, a reinforcing mesh, and a finish coat. Total render thickness is usually in the region of 3–5mm.

Addressing Common Issues

Cracking

If your render develops cracks, it could be because it is too thin, dried too fast, or the wall to which it’s been applied has moved. If you want to repair it, you will most likely need to fill in the cracks or apply a new layer of render.

Bubbling

Bubbling is a problem when the render fails to adhere to the wall. Air or dampness can become locked in behind the render. You have to take it out and put it back in.

Sagging

A “sagging” occurs when the render applied is too great at one time, or too wet. Using thinner coats can be helpful.

Uneven Texture

Texture irregularity is often a surface problem that requires recoating.

How thick should render be on bricks?

A 20-25mm thickness of cement render is commonly applied to brick walls. This gives good protection as well as a nice finish.

How thick can an acrylic render be?

Acrylic render is far less susceptible to cracking and can be applied in a thinner coat compared with cement render. Two layers are usually enough for a 3-4mm total thickness.

What if render is too thick?

Render that is too thick can be heavy, crack or fall off. It can also be wasteful of material and expensive.

Can I apply render in one thick coat?

One thick coat of render is not recommended. Several thin coats provide good adhesion and reduce the chance of cracking or sagging.