How to assemble and install a sandwich chimney with your own hands: installation instructions

Sandwich chimneys have many advantages: lightness of construction, safety, aesthetic appearance.Why not try to assemble a sandwich chimney with your own hands? As practice shows, it is really quite simple. And everyone can build such a chimney like a construction set.

This work will require knowledge of the structure of the chimney and its installation - we discussed this material in detail in our article. We selected photos and diagrams describing the main elements of the chimney system, and provided step-by-step instructions for assembly and installation.

We also supplemented the material with useful tips for improving draft and a video demonstrating the process of installing a chimney in a country house.

Pros and cons of using a sandwich chimney

Disadvantages of chimneys assembled from sandwich pipes:

• failure of sealing after a certain number of heating and cooling cycles;
• compared to a brick structure, a sandwich chimney has a higher cost;
• The service life is about 15 years, while traditional fire brick chimneys last 10 years longer.

This short service life is mainly due to the use of low-quality materials in production.

Choosing products from a trusted brand is the first thing you can do for long and successful operation of your chimney.

The advantages of sandwich chimneys are as follows:

• Insulated walls. Thanks to thermal insulation, even a chimney placed outside does not lose draft. Multilayer walls prevent the rapid cooling of combustion products, which are quickly removed through the chimney, and this prevents condensation and soot from actively forming.
• Easy installation. Having studied the principles of chimney construction, even a beginner can assemble them.
• Variety of options. To assemble the structure, straight and corner modules are produced. The chimney can be led up or into the wall; it can go around the rafter system and various architectural elements.
• Minimal soot settling. Thanks to the smooth surface of the pipes, ash and soot are released into the atmosphere faster and accumulate more slowly.

In addition, the sandwich system is relatively lightweight, which means it is easier to create a support for it and does not require the construction of a special foundation, as for a brick chimney. It can be attached to ceilings and walls, or installed directly on heating equipment.

Compared to single-wall chimneys, sandwich chimneys almost do not form condensation and are fireproof.

Even the most complex structure can be assembled from standard sandwich chimney elements

Material from which pipes are made

For different heating devices and types of fuel, a different type of steel is selected. It must be highly alloyed and stainless, suitable for the manufacture of chemically resistant and fireproof chimneys.

In the construction of a chimney, one of the main characteristics is the steel grade as a criterion for long-term service and resistance to external negativity

When various substances burn, chemically active substances can accumulate in the chimney: sulfuric acid, sulfur, hydrochloric acid. In addition, the temperature during combustion of different fuels can vary greatly.

When heating with wood or gas, it does not rise above 450 °C; when burning coal, it can reach 700 °C. Metals react differently to these indicators. That's why choosing a smoke exhaust system, pay attention to the main characteristic - the quality and properties of steel.

Option #1 - stainless steel with alloying additives

The main grades of steel alloys that are used for the production of sandwich chimneys:

• Titanium stabilized stainless steel (AISI 321). Used for wood burning equipment. Not resistant to corrosion in sulfur-containing environments. Permissible operating temperature is 600–800°C.
• Molybdenum stabilized stainless steel (AISI 316). Installation of a sandwich chimney made of this grade of steel is carried out for heating installations that operate on wood, gas, or diesel fuel. The metal is acid-resistant and has increased resistance to corrosion and aggressive environments of various types.
• Heat-resistant steel (AISI 304). The inclusion of chromium and nickel makes the steel insensitive to elevated temperatures and acidic environments. Used for the production of chimneys with high temperature exhaust gases - about 1000 °C. At temperatures of 600–800 °C, it is prone to loss of viscosity and ductility, which leads to embrittlement.
• Widely used grades AISI 409 and 430 poorly resistant to high temperatures and acids.Most Chinese products and some domestic ones are made from these grades of steel.

It is impossible to check the steel grade visually. When purchasing, you can check the markings on the product itself or try to approximately determine the quality using a magnet.

Low quality material will attract a magnet, metal with added alloying additives will not.

When choosing pipes for a chimney, take an interest in their main characteristics. If you have doubts about the seller’s honesty, take a magnet with you - it will be attracted to steel products with insufficient proportions of alloying additives

Option #2 - ferrous metal for chimney pipes

The ferrous metal itself quickly wears out - it oxidizes and burns out. Therefore, special enamel is used to protect it. This increases resistance to acidic environments.

Enamel can serve for a long time at temperatures not exceeding 400 °C and can withstand short-term increases up to 750 °C.

The variety of shades of enameled pipes makes them quite popular

Enameled pipes are used to remove combustion products from heating columns, stoves, heating boilers, and fireplaces. Unlike steel ones, they can be painted in different colors. This allows you to select the right shades for the interior or facade of the house.

Option #3 - combined sandwich chimneys

To reduce the cost of production, enterprises try to use cheaper materials. If the inner pipe is made of expensive stainless steel, and the outer pipe is made of galvanized or enameled metal, then this has little effect on the service life of the product.

It’s worse if it’s the other way around: they use stainless steel on the outside, and hide cheap, low-quality material inside. With intensive use, such a pipe can last a year and fail, which will entail new costs for materials and installation.

Before purchasing, it is advisable to ask for the accompanying documents for the product to ensure the quality of the pipe you are purchasing. It is important that the internal element is made of high quality stainless steel

Between the two pipes of a sandwich chimney there is a layer of insulating material that retains heat inside and thereby maintains good draft. Basalt or ceramic wool is used as insulation - fibrous materials with the highest fire resistance class.

Basalt wool can withstand temperatures up to 600 °C, ceramic wool - up to 1000 °C. Both materials have good thermal insulation properties. A layer of insulation of 25-50 mm is used. For a chimney that is mounted outside, the larger it is, the better.

The influence of the type of fuel on the operation of the chimney

Below is a table that will help determine how to choose the right chimney for different types of heating equipment so that it works longer.

The user manual for each chimney device indicates the permissible temperature

Setting up a sandwich chimney for gas equipment, you can get by with a cheaper design option. But for a Russian or sauna stove, it is better not to save money and choose a system whose quality is beyond doubt.

Structural elements and their features

The variety of products allows us to perform complex tasks in the construction of sandwich chimneys.

Chimney manufacturers have developed more than twenty different elements to facilitate installation

The main design elements of the chimney duct are:

• Straight pipe sections. Sections with a diameter of 80-600 mm, up to 1 m long. The ideal chimney design is straight, but in practice this is difficult to achieve.
• Knees and tees. They are used if it is necessary to bring the chimney through the wall, to the outside of the building, or to bypass the structural elements of the house - beams, rafters. Sometimes, for turns (especially straight, 90°), tees with revision are used - they allow you to clean the chimney in hard-to-reach places. They are installed and reinforced with brackets so that they do not bear the weight of the structure above.
• Feedthrough pipe. It insulates the pipe from the interfloor partitions and serves as a fastening for the chimney.
• Roofing cutting. It is a metal cone that is attached to the roof at a certain angle. Helps to pass the pipe through the roof without compromising its tightness and increasing fire safety. Instead, a special silicone seal can be used, which serves as better protection against leakage.

In addition to the above elements, there are also a lot of devices for installing a chimney made of sandwich pipes, as well as its further operation.

The chimney is secured with brackets every two meters. Fasteners for fixing clamps on the wall are selected in accordance with the material from which it is made

How to choose the required chimney diameter?

The diameter of the chimney pipe is selected based on the boiler power data.

For low-power heating installations with less than 3.5 kW, pipes with a diameter of 8 cm are used, for boilers with values ​​no more than 5.2 kW, pipes with a diameter of 9.5 cm are used, and over 5.2 kW - 11 cm. Narrowing of the chimney is not allowed, but widening, on the contrary, can be carried out.

Another indicator that affects the diameter of the chimney is the thickness of the insulating layer. It can be 25-100 mm. The larger it is, the better it exhibits its properties, but its cost also increases. The thickness of the metal itself used to produce pipes can be up to one millimeter.

If it is necessary to build on, replace or modernize any section of the chimney, the consumer may find himself in a difficult situation. Elements from different brands are not able to provide a sealed joint.

When purchasing missing parts, it is better to find (order) components of the same brand as the rest of the structure.

Installation of a sandwich system for smoke removal

Before installing the structure, you must carefully read the technical documentation and safety regulations.

It is imperative to take all measures to prevent fire during operation of the chimney.

Before purchasing, it is necessary to calculate all materials, taking into account the specific layout of the house

Step #1 - assembly of chimney pipe elements

Installation of the structure always starts from the bottom up. Sandwich chimneys must not be connected directly to a heating device.

A sandwich chimney element is never connected to the heating device - a single-wall pipe or adapter is installed first

First, install a special adapter or a single-wall steel pipe half a meter long.

If it is planned to lead the pipe directly into the wall, then install a horizontal outlet with a slight slope of 2°.

The adapter is designed to connect different sections of the chimney system - single-wall and sandwich pipes

The section of uninsulated pipe can be short or long if greater heat transfer is expected. Walls and structures located near it must be protected with a screen or casing.

They install it “smoke-wise”, that is, they put it on top of the heating device pipe and additionally protect the joint with a heat-resistant sealant.

Assembly “by condensation” prevents drops of moisture from penetrating into the insulation system, which significantly reduces its insulating properties

The chimney sandwich element can be connected to the heating device through an adapter - a double-circuit pipe, the lower part of which is installed “for smoke”, and the upper part “for condensate”.

All subsequent pipes will be installed “on condensate”, which will prevent its seepage and protect against damage to the thermal insulation layer.

All joints are secured with couplings. Near every junction install a clamp, designed for mounting the system to the wall.

To prevent lateral movement of the structure, wall brackets are used every two meters, and support brackets are used for tees. The system is attached to the wall using consoles or support platforms every five meters.

Step #2 - passing ceilings and walls

Even the fact that sandwich chimneys have an insulating layer does not mean that their surface cannot heat up quite strongly. Therefore, it is prohibited to place them without additional insulation near flammable materials (wood, plastic, etc.).

The joints of sandwich pipes for chimneys during their installation and operation should not coincide with the passage in the ceiling or wall.

The free space between the ceiling and the pipe is filled with non-flammable and non-flammable basalt wool

The diameter of the hole in the wall or ceiling is cut 250 mm larger than the diameter of the outer pipe.

Make it round or rectangular. Heat-resistant material is placed in the free space, which is hidden with decorative plates.

The passage unit is heat-resistant, it prevents deformation of the chimney when the building structure moves - shrinkage, moisture and temperature deformation

To pass through the ceiling and, especially, through flammable materials, a special passage unit is also used. An air gap is left between the outer contour and the inner surface of the assembly.

When passing through a ceiling or wall made of a slightly flammable material, you can use an unloading platform instead of a passage unit. It will act as an additional support.

Step #3 - passing the system through the roof

When withdrawing chimney pipe through the roof, its tightness is broken. To strengthen the pipe, isolate it from flammable elements of the roof and eliminate the possibility of leaks in the roofing, special devices are used: conical roofs, silicone seals.

These parts have standardized slope angles; they are selected taking into account the roof parameters.

Silicone sealant - master flush greatly simplifies the work and helps create reliable protection against leaks

When placing the pipe, it is calculated so that the distance to flammable materials is at least 37 cm.To protect against water getting under the roof, an apron is installed over the roof. Its edges go under the roofing.

Step #4 - placing the structure above the roof

The height of the chimney pipe depends on the distance between the base of the pipe and the ridge, but not less than half a meter above the ridge, 1.2 m above the surface of a flat roof or 2 m with a combined roof. If the head of the ridge is one and a half to three meters away, then it should be placed above or opposite the ridge.

If the distance is 3 m or more, then it is permissible to place the head no lower than the line that is formed if you draw a horizontal line from the ridge and measure down an angle of 10°.

If the pipe head is mounted lower than required, backdraft may occur in the system.

If there is a nearby building, the top of the chimney pipe should rise above its roof by one and a half meters or higher.

A pipe of this size must be further strengthened with guy wires.

When planning the design of the chimney, take into account the type of roof and the location of neighboring buildings. The pipe should not get into the support zone, which will negatively affect the formation of draft

If flammable material was used to cover the roof, then the chimney place a spark arrester. The chimney design is completed by a cone-shaped head. Sometimes he gets protected fungus or deflector, other devices.

What to do to improve traction?

The principle of operation of the chimney is based on the creation of draft - the ventilation effect that occurs due to the temperature difference in the middle and outside of the duct.

The density of warm air in the chimney system is less than that of cold air outside and this leads to a pressure difference.Due to this difference, cold air enters the stove, and hot air rises through the chimney and goes outside.

Reasons for poor removal of combustion products

A simple way to determine the presence or absence of draft is to visually assess the presence of smoke in the room or identify the problem by the color of the fire.

Orange shades indicate insufficient draft, white flames and a hum in the chimney indicate excessive draft. Sometimes the craving may change direction for a short time.

Common causes of reverse or poor draft are a high obstruction and a low-lying chimney

Without taking into account a chimney that is not cleaned in time and is clogged, the reasons why it occurs reverse thrust, the following:

• incorrect calculation of the ratio of boiler power and pipe parameters;
• unfavorable weather conditions - fog, rain, heat, strong wind;
• a large number of narrow sections and turns in the chimney design;
• high location of the ridge in relation to the head of the chimney or nearby tall buildings;

Also for the formation of normal draft, a lack of supply air and insufficient ventilation in the house.

How to prevent problems with traction?

Here are some recommendations on how to assemble a sandwich chimney so that the heating device does not become a source of soot and soot in the house:

• the height of the structure must be equal to or greater than five meters;
• it is preferable to build a straight chimney - without bends and turns;
• turns (no more than three) are made at an angle of 45°;
• An almost horizontal section of the chimney can extend from the boiler (with a slope of 2°), but not more than one meter.

If during the operation of the chimney problems are discovered with smoke removal, they resort to installing special devices that increase draft.

It could be:

• Deflector. It works on the principle of reducing pressure as air passes around obstacles. It works effectively in windy weather, but in calm weather it can, on the contrary, hinder the removal of smoke.
• Stabilizer. It is an additional element that has the shape of an umbrella and is placed on top of the pipe. From below, air enters through the open area, increasing traction.
• Rotary turbine. It works using the force of the wind: rotating in one direction, it creates a vacuum of air above the channel. It is not effective in calm weather.

All these devices are not a panacea, especially if the chimney is not initially designed correctly.

The deflector may interfere with the removal of combustion products in calm weather

Operation of chimney sandwich systems

After installing the chimney, you should conduct a test fire to check the tightness of the joints and make sure that the adjacent structures and materials do not heat up.

When using the system for the first time, light smoke and a specific smell may appear from the heating of oil residues, sealant, and dust on the surface of the pipes.

Correct operation requires timely soot removal. When cleaning, do not use any detergents. A review of the best cleaning products and methods are discussed in our other article.

It is better if it is carried out by an organization that has a special license giving the right to carry out this type of work.

Conclusions and useful video on the topic

More information on how to correctly assemble a reliable chimney from modular sandwich pipes can be viewed in the video:

Independent installation of a chimney from sandwich pipes will require the user to study some of the nuances and subtleties. But by doing the job correctly, you can be confident in the safety of your family and yourself.

Do you have experience assembling a chimney from sandwich labor? Did you install such a chimney yourself? Share your experience with novice home craftsmen - write in the comments block what difficulties you encountered during installation, how long you have been using it and how you care for your chimney.