Comparison of the main properties
| Property | Stainless steel liner | Ceramic liner |
|---|---|---|
| Space in the flue channel | thin walls, takes up little of the cross-section | thick walls, often with an insulating jacket, needs a wide flue channel |
| Weight | light, the old masonry can carry it | heavy, needs a solid base at the bottom |
| Bends and offsets | a flexible liner also passes through small offsets | straight flue channel only |
| Fitting in an existing chimney | lowered in from the roof without breaking open the masonry | the flue often has to be opened up or widened, so it is more often used in new builds |
| High temperature and soot fires | withstands them if the steel and thickness are intended for solid fuel | very resistant to heat |
| Condensate and acids | acid-resistant steel suits wet operation | suits wet operation if the system, including the joints, is designed for it |
| Cleaning | smooth surface, cleaned with a suitable brush | smooth surface, cleaned with a suitable brush |
| If damaged | the damaged section is replaced | a cracked section often means a bigger repair |
More important than the material is whether the specific liner is intended for your appliance, temperature and operating mode. A thin steel liner that suits a gas boiler can burn through with a wood stove, and a ceramic system without moisture-resistant joints does not suit a condensing boiler.
Which liner suits which appliance
| Appliance | What we usually choose in an existing chimney | Why |
|---|---|---|
| Condensing gas boiler | acid-resistant stainless steel liner with sealed joints | cool, wet flue gases, positive pressure, condensate must be drained |
| Atmospheric gas boiler | stainless steel liner, insulated in a cold chimney | flue gases cooler than from a stove, condense in a wide flue |
| Pellet boiler | thicker stainless steel liner for solid fuel, often insulated | cool flue gases, but also ash and the risk of a soot fire |
| Wood boiler | stainless steel liner for solid fuel, or ceramic if the flue is wide and straight | high temperature, tar, risk of a soot fire |
| Masonry stove, tiled stove, wood-burning cooker | often no liner is needed if the flue is sound; if it is, a liner for solid fuel | hot flue gases, a heat-storing stove |
| Fireplace, stove fireplace | stainless steel or ceramic liner, depending on the size of the flue channel | high temperature, large volume of flue gases |
| Sauna stove | stainless steel liner for solid fuel, often insulated | very high temperature, short, intense firing |
The exact diameter and the requirements for the flue are set by the appliance manufacturer's instructions, so read them before choosing. For a gas boiler, more: liner for a gas boiler.
What the liner marking shows
Metal flues and liners are made to European standards, and the building code refers to them. The liner or its documents carry a marking that shows what it is intended for. The most important parts are the temperature class, the letter W (wet operation, with condensate) or D (dry operation), and the letter G, which means the liner has been tested for soot fires, or O if it has not. A solid-fuel appliance needs a liner marked G, a condensing boiler one marked W. Ceramic systems have a similar marking under their own standard.
LBN 231-15 (Cabinet Regulation No. 310 of 16.06.2015), point 50: flues are made of non-combustible, heat-resistant and corrosion-resistant materials. Point 55: metal flues are designed and installed in line with the applicable standards; point 84 lists the standards LVS EN 1856-1 (metal chimneys) and LVS EN 1856-2 (metal liners and connecting flue pipes). Source: likumi.lv, checked 04.11.2026.
What the fire safety regulations say
The fire safety regulations do not set the material, but they do set how often a flue must be checked and cleaned. For gas and liquid-fuel appliances, an ordinary brick flue must be checked and cleaned once a year, while a lined brick flue, a ceramic and fireclay flue or a metal flue needs this once every two years. For solid-fuel flues, how often they are cleaned does not depend on the liner: how often to clean a chimney.
The distances to combustible structures are set counting from the inner surface of the flue, but they do not apply if the manufacturer has set otherwise. For certified liners and systems the manufacturer states its own distances, and these must be followed during installation.
Cabinet Regulation No. 238 of 19.04.2016 “Fire Safety Regulations”, point 71 sets how often liquid-fuel and gas flues are checked and cleaned. Brick: at least once a year (71.1); lined brick: at least once every two years (71.2); ceramic and fireclay: once every two years (71.3); metal and other materials: once every two years (71.4). Point 64 sets the distance to combustible structures (380 mm or 510 mm), point 65 to low-combustibility ones (250 mm or 380 mm); under point 66 they do not apply if the manufacturer has set otherwise. Regulations checked 04.11.2026; from 2 January 2027 they will be replaced by new fire safety regulations, which we will check as soon as they are adopted. Source: likumi.lv, checked 04.11.2026.
How we choose a liner for your chimney
- Appliance We find out which appliance will be connected, the diameter of its outlet and the manufacturer's requirements for the flue.
- Flue We clean the flue and look at it with a camera: the cross-section, offsets, cracks, whether there is room for insulation. About this job: camera inspection.
- Material Based on all this, we choose steel or ceramic, a single-wall or insulated liner, and its marking.
- Quote We name the price before the work; materials are charged separately.
The work is done by a qualified chimney sweep, and the certificate states their qualification document. How the work itself is done: fitting a chimney liner. If the chimney is cold: chimney insulation.
Sources
- How often flues of gas and liquid-fuel appliances are checked and cleaned, by material (Cabinet Regulation No. 238, 71.1–71.4); distances and the manufacturer exception (64–66); Cabinet Regulation No. 238 loses force on 02.01.2027 checked 4 November 2026
- Non-combustible, heat-resistant, corrosion-resistant materials (LBN 231-15, 50); metal flues to standards (55); LVS EN 1856-1 and LVS EN 1856-2 (84) checked 4 November 2026