How to cover the stove so that it does not crack from the heat?

Brick oven

The brick kiln is still in demand by people. Some populated areas are not gasified and a stove in a residential building is necessary. Sometimes it is an additional source of heat in order to save gas or electric heating.

In a country house you can not only spend the summer, but also celebrate New Year, Christmas and other holidays - romantic, unusual and healthy. A simple stove or fireplace will create comfort in the house; you will want to be at the dacha on weekends, sitting comfortably in the warmth.

When installing the stove, a number of conditions must be observed. In addition to choosing the correct design, installation location, components and materials, you need to understand what stoves are coated with so that they do not crack or crumble. A responsible attitude to the work at the construction stage of the building itself and the use of appropriate quality materials does not lead to cracks in bricks and finishing materials.

Causes of cracks

Owners of brick fireplaces, having discovered a problem, rush to find out how to cover the stove in the house so that it does not crack in the future. It is important to understand that damage is caused by various reasons, and not all of them can be eliminated by cosmetic repairs. In most cases, violation of the integrity of the masonry is not dangerous and can be easily eliminated. Seams crack for the following reasons:

Irregular use. In winter, the house is heated with long breaks (for example, the owners come to the dacha on weekends). Temperature changes inevitably lead to the appearance of cracks in the seams of the furnace walls.
Violation of operating rules. Cracks cannot be avoided if the stove is not given time to stand and dry well after laying.
Design flaws. Different zones of the structure are heated unevenly, and the material expands differently when heated. Cracks run along the boundaries of areas with different temperatures.
Finishing errors. Poor quality solution selected; its layer is too thick, or, conversely, too thin.

The problem is obvious Source pechdoc.ru

Error in choosing masonry mixture. Problems arise when masonry is done with the wrong mortar, causing the thermal expansion of the brick and the mortar to mismatch. The result is a network of microcracks, which appears on the heated structure.

The question of how to coat a stove with clay so as not to crack goes to another level if the reasons for the damage are more fundamental:

Construction errors. If errors are made in the foundation design, restoration of the seams will not help, and the owners will face a major overhaul. The solidity of the furnace walls is also compromised if there are defects in the furnace design. Both options are life-threatening due to through cracks, a source of carbon monoxide.
Calculation errors. If the physical characteristics of the materials were not taken into account when calculating the seams and no reserve was left for thermal expansion, the resulting cracks create a threat of collapse. The stove structure will have to be rebuilt.

Note! Before you begin eliminating cracks, it is worth conducting diagnostics. If the cause is global, restoration makes no sense. You can start choosing a mixture if the reason is insignificant.

Cracks around the fire Source tengrinews.kz

Exterior finishing of stoves

You can increase heat transfer, hide minor deformations and give the stove a more aesthetic appearance by plastering or tiling.

Plastering is the most common; it is possible after settling and complete drying of the masonry.

Important! The walls of the oven intended for plastering should not be dirty and smooth; the solution will not have the necessary adhesion to them. The plastered surface will have defects after drying.

Tiling gives an elegant look and protects the room from the penetration of flue gases when small cracks appear in the masonry.

What causes cracks

When malfunctions of the furnace equipment are discovered during use, the first thought that arises is: the furnace is cracking, what should I do? To begin with, it doesn’t hurt to figure out what led to this.

The following factors may be the reasons:

donkey foundation or structure itself;
unscrupulous craftsmen and unprofessional work;
low quality material or unsuitable mortar for masonry or plastering was used;
the drying process of the masonry is disrupted;
long heating breaks, sudden temperature changes;
the technology was not followed when applying each layer during plastering;
The ventilation system is faulty, condensation.

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Is it possible to use a stove with cracks?

There is only one answer to this question: it is prohibited. Do not use a stove with cracks and endanger people’s lives. If there are no structural defects, it is necessary to begin troubleshooting as soon as possible.

Important! Fires in most cases result in death due to carbon monoxide released, not fire.

Diagnosis of problems

The diagnostics of all surfaces will answer the question why a brick stove is cracking. The worst option would be widening through brick cracks. You can’t do this without the help of a specialist; you may need to re-lay the furnace.

Small cracks in bricks caused by high heat allow you to carry out the work yourself. The cracks need to be filled and the surface re-plastered.

Oven adhesive

In building materials retail outlets there is a dry adhesive special mixture, as well as a ready-made solution of fireclay clay and cement. This glue is durable and fire-resistant. It is convenient to fill the voids of bricks with ready-made plastic material.

The dry composition is not difficult to dilute in accordance with the instructions. It is recommended to work with a small amount of material, as it dries quite quickly. Along with the advantages, ready-made glue has the disadvantage of being quite expensive.

Composition of materials and mixtures for the oven

You can buy a refractory mixture for puttingtying a stove ready-made.
The walls of the stove become hot during operation, so the usual mixture will crack and crumble after a few months. The raw materials for mixing refractory putty for the furnace are sand, cement, gypsum, lime and clay.

Recommendations for preparing the solution:

it is preferable to use lime or clay in the composition, but be sure to add asbestos;
Complex cement-based mixtures can be used, but asbestos or other fibers remain an additional component;
straw or hemp can replace asbestos.

Store-bought dry putties are sealed with water in accordance with the instructions on the package. The finished mixtures in buckets are pre-mixed. The amount of solution that is used before hardening and loss of plasticity is prepared.

Prepare the composition yourself to coat small fires; for large stoves it is better to purchase high-temperature mixtures prepared at the factory.

Materials

Options for the composition of the putty mixture
Sand is a sedimentary rock with a loose structure, almost entirely consisting of silicon dioxide. River, sea and quarry types can be used for the solution. Sand grains formed in reservoirs are round in shape with a smooth surface.

Clay is a sedimentary rock containing kaolinite, which when dry is dust and becomes plastic when moisture is added. Porous and waterproofing material is characterized by sinterability, fire resistance, viscosity, and shrinkage.

Lime is obtained artificially by burning carbonate rocks and includes large amounts of calcium, magnesium, and dolomite. Lime dough or a slaked variety (kipelka) is used.

Asbestos refers to mineral filaments from the group of silicates, which in nature form flexible fibers. It is classified as a carcinogen, has high heat resistance, does not dissolve, but fluffs up in water. In oven putty it serves as a binding and dispersed component.

Cement refers to astringent hydraulic inorganic substances obtained artificially. When moistened, it forms a plastic mixture, which subsequently hardens and gains strength not only in air, but also in water.

Fireproof mixtures

Competitor brands on the Russian market of refractory putties
Factory-made refractory compounds are versatile and intended for high-quality work. Manufacturers abandoned the use of asbestos due to its carcinogenic effects and replaced it with harmless components.

Common ready-made formulations:

Plitonite. The line of Russian-German manufacturers includes materials of the Super-Fireplace brand for domestic and industrial hearths. The scope of application varies depending on the composition.
Mastic Titan. The solution is prepared on the basis of stone flour with polymer additives. Heat-resistant putty for ovens firmly adheres to the surface and can withstand up to +1300°C.
Terracotta. Gray plaster sets quickly, breaks down at +400°C, and can be applied in a layer of up to 8 mm. It is prepared on the basis of kaolin fireclay clay.
Thermo +999 PRO brand. The composition is suitable for top application and for repairing the fuel compartment. The reinforced mortar can withstand +1000°C, sets in 1 hour, but fully gains strength within 24 hours.

Coating for Emelya stoves and fireplaces is made on the basis of white heat-resistant clay and kaolin. The dry mixture is diluted with water, after hardening it prevents cracks and shedding of the layer.

The Pechnik brand is a competitor to the well-known Terracotta brand, it can withstand surface heating up to +300°C, and is applied in a layer of up to 10 mm. The line includes starting and finishing mixtures.

Clay-sand mixture

Affordable economy class material. To prepare the proper quality solution, only high-quality clay and river sand are used. The clay is poured with water in a convenient container and diluted to the state of milk, then rubbed through a fine sieve.

When the clay and water settle, the liquid top layer is drained. Sand, sifted twice, is added to the clay mixture, ratio 1:2. The liquid composition is diluted from the clay mixture to a creamy consistency and mixed thoroughly.

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It’s easy to check whether the solution is ready. If small pieces of the mixture remain stuck to the stirrer, then the solution is ready, and if large enough pieces remain, then by diluting with water the mixture is brought to the required condition.

A solution containing clay is more likely to lead to defects. There are no exact instructions for preparing the solution; it is prepared based on the experience of the master. There are not many professional craftsmen, so such a solution is not often in demand.

Solutions and mixtures for restoration

External defects on the stove can be corrected using several compounds; Some of them are mixed independently, others can be purchased ready-made. Each of the compositions has its own characteristics, but all of them will reliably seal the cracks and prevent carbon monoxide from entering the room.

Fireclay putty

Chamotte is clay with fire-resistant properties, a professional option for stove restoration. Chamotte is sold in construction stores; it has valuable advantages. It is often chosen by owners when evaluating options for how to coat the stove to prevent it from cracking.

The main advantage is the combination of heat resistance and strength. After application and drying, the clay becomes vapor-tight and moisture-resistant. It is also important that fireclay is a natural, healthy material suitable for use in residential premises.

To prepare the mixture for restoration, mix one part of M-500 cement, two parts of fireclay and seven parts of river sand. Water is added until a plastic consistency is obtained. The materials are pre-prepared: sand and cement are sifted, clay is soaked in water for several hours.

Fireclay putty recipe Source tproekt.com

See also: Catalog of companies that specialize in the design and installation of fireplaces and stoves

Sand-clay mixture

An inexpensive solution for restoration is made from ordinary building clay and sand. The mixture is quickly prepared and serves as a quick solution to the problem of how to cover the stove so that it does not crack. The mixture is prepared according to the following recipe:

To obtain a solution, the clay is poured with water at the rate of one part clay to three parts water.
The clay is infused for 24 hours, then it is mixed and sifted through a sieve with a mesh size of 3x3 mm.
The solution is allowed to settle and excess water is drained. The remaining solution should have the consistency of thick sour cream.
River sand is added to the container in a 1 to 1 ratio and mixed with clay until smooth.

Then the mixture is brought to the desired condition - sand is added to it in parts; As a result, there are 2.5 parts of sand for one part of clay. If you plunge a shovel into the container and pull it out, the correct mixture remains in homogeneous clumps. After application and drying, the sand-clay layer remains flexible enough to withstand high temperatures.

Kneading clay Source notperfect.ru

Ready-made adhesive mixtures for stoves and fireplaces

Construction stores offer glue for repairing fireplaces and stoves, eliminating the problem of covering up the stove. There are two options for glue, plastic and hard, with the following composition:

The filler for all brands of glue is quartz sand.
Binder: a mixture of fireclay and sand, or heat-resistant aluminosilicate cement and kaolin,
Mineral plasticizer: fireclay fiber, liquid glass or soapstone flour (furnace or soapstone).

The main advantage of industrially produced glue is its uniform texture, which cannot be achieved at home. Different brands are characterized by different limits of heat resistance, as evidenced by their characteristics: the composition can be heat-resistant, heat-resistant or heat-resistant. The composition and temperature ranges are indicated in the instructions.

The glue is quickly prepared for use and sets quickly, so it is prepared in small portions. Plastic varieties are applied to cracks and cracks, while hard ones are intended for plastering the entire surface.

Grout adhesive Source wp.com

Fireclay clay

One of the best materials to cover the stove so it doesn’t fall off. Affordable, sold in stores, packaged in 20 kilograms. Resistant to moisture and temperature. Also intended for plastering surfaces.

The finished solution is obtained as follows: fireclay clay is mixed with cement and sand, the ratio of the components is 2: 1: 7, respectively, water is added. For better pliability of the material, you can initially fill the clay with water, then wipe out the lumps, add cement and sand. The thickness of the mixture depends on what type of work is being carried out, and skill experience also plays a role.

Sequence of work

The first time the cracks are plastered or covered is no earlier than six months after the stove has been installed. It is necessary to wait for the natural shrinkage and shrinkage of the materials, otherwise the restoration will have to be repeated. Having decided the question of how to coat the stove, it is important to do it correctly. The work consists of the following stages:

Cracked seams are opened: they are deepened by removing the plaster. This will help fill a larger area with the solution and increase adhesion (quality of adhesion).

Firing the furnace Source blogspot.com

The prepared surface is treated with a deep penetration primer (it can be replaced with water). Then the stove or fireplace is heated with a small pile of firewood. The flow is an important part of the technology; it dries the surfaces prepared for restoration.
While the walls remain warm, a base is applied to the working surface: a liquid clay solution. The clay is applied with a paint brush and allowed to dry.
A reinforcing fine-mesh mesh is laid on top, which is fixed with self-tapping screws. An alternative to mesh is old burlap. It is glued or fastened with nails in the joints between bricks.
The selected mixture (factory or homemade) is applied in two steps. The thickness of each layer of plaster is 4-5 mm.
After the plaster has dried, it is rubbed down, the walls are painted with a chalk composition or whitewashed with liquid lime.

Whitewashing a stove with lime Source ytimg.com

Oven grout

To eliminate defects that occur in the oven, ready-made heat-resistant grout is sold. Because of its high cost, home craftsmen prefer to make such a solution themselves.

The clay is prepared as for a clay-sand mixture. The soaked clay slurry is combined with sifted sand and while mixing, chopped straw is added, the component ratio is 1:4:5. 1 kg of coarse salt is added to the finished solution, which makes the composition more plastic and resistant to cracking.

Grout perfectly fills voids. You can also use it to plaster the stove surface with the first rough layer.

Restoration of a metal stove

Fireplaces and stoves made of metal can also crack. Owners do not always notice cracks on the walls due to their small size, but such a defect is signaled by the smoke that appears in the room during the fire.

In such cases, a welding machine will not always help. The problem is easier to solve with the help of a special putty-sealant, ready-made or made by yourself.

The basis of purchased heat-resistant sealants is silicone; additives determine the properties of the paste:

Fire-resistant grades contain iron oxide; such compositions have a reddish-brown tint. They are used where the heating is maximum.

Applying sealant Source insales.ru

Neutral sealants are needed at the joints of brick (concrete) and metal elements. When drying, they lose moisture and alcohol, after which they acquire the necessary strength.
Acidic compounds are not used on metal surfaces. As they dry, they release acetic acid and start the corrosion process on the metal.

There are recipes for making your own sealant paste. They are quite complex in composition and require precise proportions between ingredients. However, the result is not always acceptable, since the components may contain impurities.

Only high-quality materials Source rusolymp.ru

Covering stove cracks

The material for the upcoming work has been selected, and another question arises: how to properly seal the stove?

You can start working only after cleaning the brick from decorative finishing and plaster. Using a suitable tool, the gaps between the masonry with cracks are widened to fill an area of about 10 mm with adhesive.

When using ready-made adhesive solutions, it is advisable to adhere to some rules:

prepare the working solution in a limited volume due to the drying speed;
Wet all cracks with water;
tightly fill the gaps with adhesive;
Lubricate the top of the oven with the prepared solid mixture;
wait for it to dry completely and start plastering.

An unheated stove is a bad option for carrying out repair work with materials containing clay. It is recommended to heat it slightly; this will help you see imperfections and eliminate defects before the putty dries.

The sequence of work will be slightly different:

Before sealing the cracks, stir the mixture again until smooth (the contents have different densities);
make sure the material is of high quality. To do this, you can manually make a spherical object, and if cracks appear on it, add a little water;
wet all the cracks with water and fill tightly with glue (it’s safer to use your hands);
Plaster also after final drying. Next you can use whitewash.

How to seal a stove to prevent cracks

You picked up the most expensive heat-resistant mortar in the store, your stove is on a solid foundation, but new cracks still appear. Don’t rush to immediately blame the putty manufacturer - the point is not what to cover the stove with, but how to cover it! Hasty completion of work without observing all the nuances is the second reason for the appearance of cracks.

Firstly, you need to putty the stove by heating it slightly. Secondly, the cracks that you want to cover up must be moistened generously with water; without this step, the dry masonry will suck all the liquid out of the fresh mortar, as a result of which it will not gain the required strength. And thirdly, do not rush to light the stove - you need to wait until the putty has completely dried! Only compliance with these nuances will allow you to forget about new cracks forever.

Oven overheating

Having installed a new stove, or repaired damage to the old one, you should not test its strength by heating it to its fullest.

The first fire must be carried out with a small amount of firewood, increasing the amount each time. And then there will be no need to get rid of the next problems again.