Expanded clay stucco plastering: technology of work

Gusevsky Andrey Anatolyevich

Plastering walls from expanded clay concrete blocks

Plastering claydite-concrete walls can cause difficulties, which is associated with the formation of numerous cobweb-like cracks, and sometimes peeling of the coating when it dries or after some time. In addition, significant shrinkage of the material may appear, and as a result, the surface will repeat the relief of the existing masonry instead of leveling and hiding its defects.

Like how to plaster the walls from expanded clay blocks, the proposed article will introduce.

Features of expanded clay blocks

The construction of expanded clay blocks of houses and other structures has long been used by the owners of their plots. Blocks are made of several components by vibropressing. Expanded clay is a foamed and baked clay, sand and cement, carefully mixed, compacted using high-pressure vibration loads.

Features of the surface and structure of the blocks are:

• The composition of the material is foamed gas or diluted granules of concrete insulation, which makes the material structure heterogeneous with many pores, moisture is actively absorbed through them. This violates the normal ripening regime. stucco mortar, it will dry out and crack.
• Unfilled pores absorb moisture with the solution, which leads to severe shrinkage of the layer. This violates the geometry of the surface, the wall becomes a curve, masonry joints and block contours can appear on it.
• The presence of a large number of pores and inclusions of foreign materials weakens adhesion when coating the surface. Without timely measures to improve adhesion, the finish will quickly crumble and fall off.
• The material of the blocks is highly vapor permeable.

Tip: The vapor permeability, when decorating the walls, should increase from inside to outside, before plastering expanded clay blocks, the coating material should be correctly determined.

• Strong absorption of moisture by aerated concrete requires the use of a moisture-resistant, durable, frost-resistant and elastic coating for the exterior of a house. This corresponds to polymer-cement mixtures.

To erect a structure from such material is faster and more economical than from ordinary brick.

The main disadvantages of houses made of such material include:

• Not too presentable appearance.
• The porous structure of the block is easily blown.

The advantages of expanded clay blocks include:

• Light weight, up to 8 kilograms, facilitates the construction work without outside help.
• The increased durability.
• Absolute non-toxicity of expanded clay blocks, which makes the materials the most environmentally friendly when building a house.
• Poor moisture absorption, which prevents exposure of the blocks from steam and water, which distinguishes them from wood.
• Excellent thermal insulation properties, allow you to keep heat well inside a room such as a bathhouse without too much insulation work.

General view of expanded clay block

To ennoble the building and prevent its blowing, it is necessary to perform plastering of expanded clay concrete walls on both sides.

In addition, expanded clay blocks are finished with:

• Necessities to additionally insulate the room (see Finishing and insulation of the facade of the house: choose the material): external plaster is produced, which includes insulation and a vapor-permeable membrane, or without them.
• Residential building construction: finishing it inside and out.
• The construction of basement floors, basements, other underground structures - a special waterproofing coating is made on the outside of the walls.

Material requirements for stucco blocks

When making cellular concrete with your own hands, the right choice of materials is of great importance. The solution must meet a number of requirements.

Have:

• High strength. The cellular blocks are not durable, which requires their protection against wear, abrasion, mechanical shock, scratches and other damage.
• Good moisture resistance. Pores on the surface actively absorb moisture, due to which the wall gets wet, this requires an external finish to be made with a waterproof layer.
• Adequate adhesion. Otherwise, the composition will simply fall off. It is better to use mixtures made on the basis of cementitious cementitious composition and various additives that increase adhesion.
• High ductility. It is necessary that the layer can withstand small surface changes in geometry arising from temperature extremes and shrinkage. For these purposes, the composition should contain polymer plasticizers and other elements that make the dried layer sufficiently flexible.
• Frost resistance.

Which plaster is suitable for expanded clay walls

The surface of the building from such blocks, depending on the purpose of the room, is covered:

• A solution made on the basis of sand and cement (see The optimal ratio of cement and sand for plaster) The price of such a composition is relatively small, and its purchase is available to everyone.
• Special cement-based mixtures with various additives, plasticizers and fillers. It is more convenient to work with such plaster, it is more durable, has a number of positive characteristics.
• Water repellent compounds. It is used to protect the walls of buildings erected in difficult climatic conditions, or surfaces below the ground zero.
• Gypsum-based solutions. They are used only for interior plastering of residential premises with normal humidity.

Tip: The main requirement for any type of finishing material is the possibility of applying it with a thick layer, and the presence of good vapor permeability.

Features of gypsum plaster for expanded clay concrete houses

Gypsum plaster application

Some features of the application of gypsum plaster:

• The basis of the blocks is cement, and plaster - gypsum.
• These two materials have different acidity or pH levels.
• Expanded clay has an alkaline reaction, and gypsum gives an acidic one. When mixing such media, a neutralization process takes place.
• After application gypsum plaster a neutralization reaction takes place on a wall of expanded clay concrete blocks. As a result, strength is lost at the media boundary, which can lead to delamination of the plaster.

To solve this problem you will need:

• Prime the surface of the walls well with primers specifically designed for concrete substrates. Wherein:

1. the first layer is diluted with water so that the composition penetrates deep into the material, creating a reinforced layer;
2. after the first has dried, an undiluted second is applied, creating the desired film on the boundary between the media separations.

• Gypsum plaster is used.

Tip: Priming the surface of the walls must be performed, for any type of finish, which significantly increases the adhesion of the plaster and the foundation.

Expanded clay walls can be finished with any ready-made dry mixes used for buildings from gas silicate or foam concrete blocks with high vapor permeability (see Stucco for cellular concrete: how to choose).

How to apply plaster on a wall of expanded clay concrete blocks

Instructions for applying plaster offers:

• Clean the surface of the wall from dust, dirty and oil stains, grease, old finishes.
• Seams and cracks are putty flush with the overall plane of the wall. For this, a cement-sand mixture or a ready-mixed plaster solution is used, you can purchase putty for joints.
• The wall remains to dry.
• The surface is thoroughly primed.
• The primer must dry completely.
• Preparing cement milk or mortar from cement and water.
• The composition is applied with a brush to the surface, while strokes are done horizontally, which will increase the adhesion between the materials.
• A reinforcing mesh is packed on the wall.

Tip: If there is no mesh, it should be replaced with steel U-brackets or thin metal anchors with wide washers.

• Beacons are set, their control is carried out by a plumb line or level, with a step of profiles of approximately 1.5 meters, in order to work with a two-meter rule.
• Lighthouses are mounted on a cement mortar.
• In a wide tray, as in the photo, a trough or other container, a plaster solution is prepared.
• Stirred with a mixer or spatula to the consistency of mashed potato liquid.

Preparation of plaster

• The solution is poured onto the wall with a bucket or trowel, the layer is smoothed over the beacons by the plaster rule from the bottom up. In this case, the rule moves slightly from side to side.
• After 7 hours, until the first layer has set, the beacons are removed.
• The finish layer is applied with a grater or trowel, filling the mixture with all the bumps.
• After setting the finish, the surface is rubbed with a stucco, moving it in a circle or in a run.
• After the plaster dries, the wall is primed and painted again. You can surface the surface with decorative putty or any other material for decoration.

What features have expanded clay walls, plastering them with different compositions, everyone can see in the video in this article.