Plaster on foam concrete blocks: do it yourself

Because foam concrete blocks are lightweight and have insulating qualities, working with them can be a great option for construction and renovation projects. But if you’re not familiar with the procedure, plaster application can be a little challenging when it comes to finishing these blocks. If you intend to do this task yourself, knowing the fundamentals will help you accomplish a polished, seamless finish.

We’ll walk you through the process of plastering foam concrete blocks by yourself in this guide. In order to help you complete the task correctly, we’ll go over crucial advice and methods for everything from plaster application to surface preparation. Regardless of your level of experience with do-it-yourself projects or your desire to cut labor expenses, this post will arm you with the knowledge you need to produce a flawless finish.

You can improve the look and longevity of your foam concrete block walls with the appropriate strategy and helpful guidance. Now let’s get to work and begin transforming your area with a new coat of plaster.

Foam blocks and plaster

Casting-derived foam blocks require sanding beforehand due to their extreme smoothness, and high adhesion index mixtures should be used during the process.

Particular characteristics of foam concrete:

• Durable material
• Possesses high resistance to temperature changes
• Has excellent heat conservation and sound absorption
• It has a minimum shrinkage coefficient
• Lightweight building material, therefore it is convenient to work with and transport
• It has good water repellency
• Easy to process and cladding

Attention: Keep in mind that you run the risk of eliminating all of the advantageous qualities of this special building material if you do not follow the technology of applying the plaster mixture.

The important thing to realize if you want to plaster foam concrete blocks yourself is that, even though it’s a do-it-yourself project, it does require some careful planning. To ensure that the plaster adheres properly, first make sure the block surface is clean and clear of dust. Then, apply an appropriate primer. The plaster should then be mixed and applied in thin, even layers, letting each coat dry completely before applying the next. By using the appropriate methods, you can improve the insulation and look of your walls with a smooth, long-lasting finish.

Features of work

These days, foam concrete blocks are a common choice for construction because of their low weight, high thermal insulation, ease of installation, and affordability. It is currently a strong rival to other building materials. When it comes to performance, foam concrete is comparable to wood because it conducts heat less than brick.

• Foam concrete consists of sand, foam and water. Foam is the main component and gives the material unique properties. Foam concrete is used to build not only houses, but also baths (see. Baths from foam blocks: interior decoration – do it yourself). Foam blocks are suitable both for the construction of partitions inside the building and for the construction of individual load-bearing structures. The structure of the material is porous and this introduces its own peculiarities into the rules of work.
• Plastering and painting are the most popular methods of facing a house made of foam blocks. However, when plastering walls made of foam concrete blocks, some difficulties arise.

Note: The primary issue with well-executed plastering of foam concrete block walls is inadequate plaster adhesion, or bonding, to the wall surface. It’s important to apply the material properly and give it time to cure, so don’t skimp on any steps in this process.

• It is difficult to plaster a foam block with high quality using conventional sand-cement and lime mixtures (see. Preparing your own lime plaster solution). They are usually used for rough plastering, when you need to save money during construction work. In this case, there is a risk that the plaster will simply fall off.
  It is especially difficult when it becomes necessary to apply a layer of plaster more than 3 cm on foam blocks or you need to plaster uneven walls.

However, just like in any other industry, there are tricks to this trade, and by using them, you can greatly increase the adhesiveness of walls composed of foam concrete blocks. If you choose to plaster foam blocks by hand, we suggest that you follow these guidelines:

• It is rational to use special liquids when plastering foam blocks that improve the adhesion of the foam block: concrete contacts or primer paint.
• It is necessary to use a reinforced plaster mesh when working. It prevents cracking of the plaster layer when the building subsides.
• Before plastering, you can sand the surface of the blocks with sandpaper. (cast blocks)

Note: All of the advice is predicated on the foam blocks’ exterior being impregnated with an agent that confers water-repellent properties. As a result, the walls won’t become damp and wet inside during periods of rain or snow outside. Thus, keep in mind that sanding this layer removes the material’s ability to withstand moisture.

Applying plaster mesh

Using construction mesh will help the plaster for foam concrete adhere well. Although it is not expensive, there will be a noticeable return.

• It is better to choose a polymer plaster mesh for applying plaster indoors, for example, plastic (see. Plaster mesh plastic: features of the material), since it is more economical, lighter, and does not corrode. As a result, the plaster will be more durable and of higher quality.
• Metal meshes rust and cause yellow spots on the plaster. The main thing when plastering is to be able to fix the mesh as close to the wall as possible, this determines the thickness of the plaster layer that will be obtained when applying the mixture.

Why is plastering an foam-block wall necessary?

• Improving the appearance.
• Protecting the wall from temperature changes
• Improving thermal insulation properties
• To allow steam to pass freely out
• Protection from precipitation, moisture and dampness
• To prevent the saturation of walls with carbon dioxide and dust and ultimately prevent their shrinkage

Mixtures for plastering foam concrete blocks

We will now take a closer look at foam concrete. Good adhesive qualities are the primary requirement that a plaster solution for a foam concrete block must fulfill.

Because of this, plaster mixtures for foam blocks are lighter, which makes it easier for them to stick and overcome the block’s poor adhesion. For plastering foam blocks, reputable manufacturers offer a variety of mixtures.

The following combinations are the best in terms of both price and quality:

• Sh-36 "Decor" – the mixture consists of cement and reinforcing fibers. This plaster mixture is easy to lay down and holds up well.
• Egida 42 and 35 (series "Pobedit") – high-quality plaster mixture
• Glims Velur – Durable plaster, does not crack when the walls shrink.
• «Ceresit CT24» – Economical, but at the same time very high-quality mixture. Very popular for its ease of use and good performance properties.

Additionally, you must choose the composition. The following details will be helpful in this regard:

• Gypsum putty mixtures are the most economical, suitable for dry rooms where there is no high humidity, since under these conditions they peel off. Therefore, these mixtures are not used for repairing bathrooms and basements.
• Finishing polymer mixtures, when dried, give a smooth surface, sometimes not even requiring wallpapering after gluing. However, their price is more than 2 times more expensive than that of conventional finishing mixtures.
• Foam blocks are made from cellular concrete in several ways: casting and sawing. For plastering, it is preferable to use sawn foam blocks, since the plaster mixture adheres to them more easily.

Pay attention: You want to obtain a completely homogenous mass when preparing the plaster composition. Thus, for mixing, use a mixer or a drill with an attachment. After that, the mixture will be quickly and effectively prepared.

Dew point and the troubles associated with it

Foam blocks are becoming more and more popular because of their excellent thermal insulation qualities and low thermal conductivity. A small amount of cold can still pass through the glue and wall material.

Plaster on the outside keeps the wall from freezing. However, if there is an overly thick layer of plaster inside, the blocks won’t be able to warm up to the proper temperature in the winter, which will lead to the dew point.

Be aware that it forms when warm air from the inside plaster layer and cold air from the wall collide at the edge of the foam concrete blocks. Dew point results in persistent moisture in the walls and mold beneath the wallpaper, giving the room a messy appearance and disrupting the microclimate.

In order to prevent dew point issues if you are putting in the puttying yourself, adhere to this basic rule: the thickness of the plaster layer inside should be twice that of the plaster layer outside, or 1:2. You can remove too much moisture from the living area by moving the dew point to the outside of the wall in this condition.

Tools for plastering foam concrete blocks

Plastering foam blocks requires the same tools as similar work with other materials (see Tool for plastering walls: what you need for the job).

• Drill equipped with a mixer attachment. Needed for whipping the mixture to the desired consistency
• Spatulas of various sizes – for applying the plaster mixture
• Level
• Rule
• Roller or large brushes for covering foam blocks with primer.

Advice from professionals

It’s not that hard to plaster foam concrete blocks, but this is no easy feat.

Professionals offer their suggestions in the following format:

• Plastering inside the house should be done no earlier than a month after the walls of the house have been raised. It is known that if the block walls shrink considerably, the plaster may crack and collapse.
• The best temperature for this work is from 5 to 30 degrees. Plastering work cannot be carried out at zero degrees and below.
• Prepare the surface before applying the mixture: clean it of dirt and oil stains
• When plastering in several layers, the next layer should be applied only after the previous one has completely dried.
• It is necessary to apply a primer both to the blocks themselves and to the surface of the plaster outside.
• The thickness of the internal plaster on the foam block should be no more than 10-15 mm. The consumption of the mixture in dry form per layer of 1 cm in thickness will be approximately 1.1 kg per sq. meter of surface. When applying in one layer, the amount of primer needed is 150 g / m2.

Plastering foam concrete blocks is an easy do-it-yourself project that can improve the appearance and longevity of your walls. There are a few essential steps you must take to ensure a polished, seamless finish that enhances the aesthetics and value of your area.

First, make sure there is no dust or debris on the surface of your foam concrete blocks. A surface that has been properly prepared gives the plaster a better adhesion and a more uniform finish. Additionally, you can strengthen the plaster’s hold and avert further problems by using a primer or bonding agent.

Consistency is key when mixing and applying the plaster. A smooth, workable mixture that spreads readily without running is what you want. Apply the plaster thinly, waiting for each coat to dry completely before applying the next. This guarantees a consistent finish and helps prevent cracks.

Plaster on foam concrete blocks can produce excellent results if you are patient and pay close attention to detail. It not only makes your walls look better, but it also gives your house more insulation and protection.

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