How To Properly Prepare A Wall From A Foam Block For Plaster

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Video: How To Properly Prepare A Wall From A Foam Block For Plaster

Video: How To Properly Prepare A Wall From A Foam Block For Plaster
Video: Prepping a wall for plaster expanding foam trick! How to prep a wall for plaster foam hack top tip!! 2023, October
How To Properly Prepare A Wall From A Foam Block For Plaster
How To Properly Prepare A Wall From A Foam Block For Plaster
  • Internal plaster of the foam block: how to do it right?
  • Features of foam block walls
  • The need for plaster
  • Preparation for work
  • Stages of plastering
  • Plastering
  • Features of work
  • Summing up
  • Video on the plaster of gas blocks and foam blocks

Plastering the foam block inside the building is an important stage in the repair. With their help, the wall material is protected from the effects of moisture and, thus, retains the main parameters - vapor permeability and lightness. When performing work, the main thing is to choose the right material and follow the technology.

Internal plaster of the foam block: how to do it right?

Walls are one of the main elements in the construction of any residential building. And one of the most popular modern materials for them is foam concrete. The advantages of foam blocks are their affordable price, lightness and good thermal characteristics. However, in order to preserve the advantages of the enclosing structures, they should be finished. The main way for this is to plaster the foam block from the inside and outside. Moreover, given the high humidity that is created during the work, the interior decoration is performed first.


Features of foam block walls

Due to the fact that aerated concrete is made from a cement mortar, into which micro-air bubbles are involved using a special technology, one of its characteristics is the ability to "breathe". This, in turn, allows you to ensure an optimal level of humidity in the premises. Another plus is high fire resistance and, at the same time, water resistance. Thus, during a fire, foam blocks do not burn, and when water hits the walls, it evaporates quickly enough without harming the structure.

It is worth noting the absence of mold on the foam concrete walls, and high heat and sound insulation properties. Therefore, such material will be the best option for housing in northern latitudes, and for a building on a busy noisy street. Moreover, the construction of structures from foam blocks is faster and cheaper due to their lightness - neither an expensive and overly strong foundation, nor heavy lifting equipment is required to build a house. Moreover, the owners of the building will be able to save money on heating and further repairs. And one of the few problems that can arise during the construction process is the plastering of walls from foam blocks, which must be done correctly, accurately and using suitable materials.

The need for plaster

On the one hand, such a stage as plastering the walls of foam blocks inside and outside could have been avoided. However, in this case, the following problems may occur:

  • unprotected structures will be exposed to sudden temperature changes and precipitation, gradually collapsing and losing their qualities;
  • increasing humidity will increase the weight of the walls and lead to subsidence of a house whose foundation is not designed for such loads.

Another disadvantage of an unplastered block is manifested only in cast products and consists in a too smooth surface on which not every putty is supported. For this reason, foam concrete is finished only with special materials. And before finishing, they must be primed, removing seams and possible irregularities (which are found even in cast foam blocks, but are especially characteristic of cut ones). However, after the plastering of the foam blocks inside is made, in accordance with the technology, the walls become not only protected, but also perfectly flat.

Preparation for work

Before plastering the foam block, you should choose the right tools and materials. First of all, when performing work, one cannot do without the plaster itself, a primer material and a special mesh. And the inventory that is needed to complete the work includes:

  • construction mixers;
  • buckets;
  • spatulas;
  • levels and plumb lines;
  • dowels;
  • washers;
  • nails;
  • spatulas;
  • metal brushes;
  • knives and rules.

When choosing how to plaster the walls of foam blocks inside, pay attention to the primer. This material is chosen from mixtures specially designed for finishing foam concrete, which must have certain properties. Firstly, a high degree of adhesion, in order to ensure a better degree of material seepage into the block. You can find such primers in the product range of such brands as Knauf, IVSIL, UNIS and Prime-Primer.

As a plaster on the internal foam block, you can use a self-prepared mixture, which contains chalk, cement and lime. However, having most of the characteristics suitable for finishing foam blocks, it will have one important drawback - instability to frost and fire. Therefore, for interior decoration it is recommended to give preference to ready-made plaster mixes of such brands as Ceresit CT24, EuroMix or Mask mix. These materials are also recommended for exterior walls. In more detail, how to prepare a wall for plastering with cement mortar.

Name A type Packing, l approximate cost
Ceresit CT 19 Water-dispersive, for processing walls made of foam concrete fifteen 730 RUB
Litokol PRIMER Cm Deep penetration for interior work ten 720 RUB
Thomsit R 777 Strengthening primer for absorbent substrates inside buildings ten 860 RUB
Putzgrund RD313 Acrylic diluent interior and exterior primer ten 800 RUB
Terragrunt 20 1620 RUB
LACRA Primer Universal deep penetration Impregnation with anti-mold additives ten 440 RUB
Tikkurila Gravel Strong Water-borne, deep penetrating acrylic primer with sanitizing and strengthening effect, facade ten 1400 RUB

Stages of plastering

The first stage of plastering walls from a foam block indoors is to clean the base with a metal brush. Carefully cleaning the surface from dust, you should pay attention to oil stains. Having found such a defect, it is removed with the help of clay, which is first applied and then removed from the oily area. If after such a procedure a stain remains, it should be cut out by filling the hole with a solution.

Using a primer
Using a primer

After cleaning, they are taken for a primer. First, a base coat is applied to the wall and allowed to dry. It is advisable to use it to obtain a smoother surface, and after applying the solution with a spatula, level the surface to remove excess and add them to the remaining empty places. The second layer is applied to the dried first layer. This stage is no less important, since the main task of a primer for foam blocks for plastering is to create conditions that are most suitable for connecting blocks and plaster.

foam block plaster
foam block plaster

Regardless of the unevenness of the walls, it is advisable not to make the primer layer thicker than 2 cm. If the enclosing structures have too large differences, they should be eliminated by installing drywall.


A further technique, how to properly plaster foam blocks, consists in performing the following actions:

  1. Preparation of plaster - pouring the dry mixture into a suitable container (bucket or tank) and stirring with an electric drill with a special nozzle to a consistency reminiscent of sour cream;
  2. Installation of a grid, which is indispensable if the walls of the house are made of cast foam blocks. Reinforcing material is attached and stretched using dowels;
  3. Application of the first layer of plaster;


  1. Waiting for the already applied material to dry;
  2. Laying the finishing layer, which should be thinner than the first;
  3. Final finishing of the premises. If painting work is chosen for this, preference should be given to special silicate paints with increased vapor permeability.

In detail: how best to plaster the foam block, read here.

To maintain the vapor permeability of foam blocks, when we plaster the foam blocks inside, the thickness of the inner layer should be no more than 20 mm. In this case, the thermal conductivity of the wall is uniformly increasing. And moisture, without lingering inside the structure, comes out without causing damage to the finish and the appearance of mold.

Features of work

An important point when performing plastering work is the observance of a certain period from the beginning of the construction of the building. Due to the fact that foam concrete immediately after production has a high humidity exceeding the permissible value during operation, it is recommended to plaster it not earlier than six months after the construction of the walls of the house.

Other nuances of finishing include:

  • the need for preliminary sealing of wide joints long before plastering foam blocks inside the room. This will save time if noticeable irregularities on the walls have to be primed repeatedly;
  • the impossibility of using cement plaster, the characteristics of which do not meet the requirements of finishing materials for foam concrete (it is desirable that the mixtures have the same permeability with the blocks);
  • the need to lay a reinforcing mesh with an overlap of at least 10 cm, as a result of which the layer is closed. Failure to comply with this recommendation may lead to an increased likelihood of the finishing layer falling off some time after completion of the work.

Summing up

It is possible to ensure a high-quality result and a long service life of enclosing structures only by adhering to the requirements of technology and using suitable materials. By doing everything right, you will get well-plastered walls that can protect the building from moisture and frost. And the house itself will stand much longer, keeping the temperature and humidity comfortable for its inhabitants inside. Watch a video on foam block plaster in different ways.

Video on the plaster of gas blocks and foam blocks







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