Last updated: 10 April 2026
Flue liner (wkład kominowy) selection is determined by the fuel type, operating temperature of the appliance, flue gas moisture content, and the physical configuration of the existing chimney shaft. In Poland, flue liners must comply with EN 1457 (ceramic liners) or EN 1856 (metal chimneys), and any relining work must be signed off by a licensed chimney sweep (kominiarz uprawniony) before the appliance is commissioned.
The most common relining scenario in Polish residential buildings involves an older brick chimney that was originally designed for a gas appliance or open coal fire. These chimneys typically have rectangular cross-sections of 14×14 cm or 14×27 cm and need to be assessed for compatibility before any lined appliance is connected.
Material Types
Ceramic Liners (Systemowe Wkłady Ceramiczne)
Ceramic liners consist of round or oval fired clay sections, typically 33 cm long, jointed with acid-resistant mortar. They are classified under EN 1457 by temperature resistance, condensate resistance, and soot fire resistance. The standard classification code reads as: T[temp]–N[normal/acid]–D[dry/wet]–V[soot fire resistance].
For wood-burning applications, the minimum specification is T400–N2–D–V2, which indicates resistance to 400°C continuous operation, high condensate resistance (N2), wet service conditions (D), and soot fire resistance at 1000°C (V2). These liners are best suited to straight or near-straight chimney shafts with offsets no greater than 30 degrees.
Flexible Stainless Steel Liners
Flexible double-wall steel liners (przewód elastyczny dwuścienny) are used when the chimney shaft has offsets exceeding 30 degrees, when circular ceramic sections cannot be manoeuvred during installation, or when refurbishment must be completed quickly. They comply with EN 1856-2 and are classified by temperature class and corrosion resistance class.
For solid fuel, grade AISI 316L (1.4404) is the minimum corrosion resistance class. For wood with expected moisture content above 20%, grade 904L (1.4539) is preferable as it offers superior resistance to organic acids produced during condensation of wet flue gas. Outer diameter of the liner must not exceed 80% of the narrowest point of the chimney shaft to allow for the annular insulation layer.
Pumice Liners (Wkłady Pumeksowe)
Pumice-aggregate concrete liners are a cost-effective alternative for straight shafts in new construction. They are cast in 500 mm sections and have lower thermal mass than ceramic, which means they reach operating temperature faster but cool down more quickly after the fire is extinguished. EN 1457 applies; the T250 temperature class is the typical minimum for pumice liners used with wood-burning appliances in Germany and Poland.
Diameter Sizing
Flue liner internal diameter is sized to match the flue outlet of the connected appliance. For most wood-burning inserts and stoves in the 5–20 kW range, the standard flue outlet is 150 mm or 180 mm. The liner diameter should match this exactly — undersizing restricts draw and causes incomplete combustion; oversizing reduces flue gas velocity and promotes condensation and tar deposition.
EN 13384-1 provides the calculation method for chimney sizing based on appliance output, flue gas temperature, and chimney height. The calculation checks that the available draught (Pa) exceeds the pressure loss through the system. For a standard 150 mm ceramic liner in a 6-metre chimney serving an 8 kW insert, draught is typically adequate without supplementary calculation, but this should be confirmed when the chimney height is below 5 metres or above 15 metres.
| Appliance output (kW) | Recommended liner diameter (mm) | Minimum chimney height (m) | Material class (wood) |
|---|---|---|---|
| 4–8 | 150 | 4.5 | T400 N2 D V2 |
| 8–12 | 150–180 | 5.0 | T400 N2 D V2 |
| 12–20 | 180–200 | 5.5 | T400 N2 D V2 |
| 20–30 | 200–250 | 6.0 | T450 N2 D V3 |
Condensation Resistance Classes
Flue gas from wood combustion always contains water vapour. When the flue gas temperature drops below the dew point of the gas mixture — typically 55–65°C for wood — condensation forms on the liner wall. This condensate is slightly acidic and contains creosote compounds; it accelerates corrosion of metal liners and leaches through ceramic joints if the mortar specification is incorrect.
EN 1457 defines two condensation resistance classes: N1 (low resistance, for dry-burning gas appliances) and N2 (high resistance, for solid fuel and oil appliances). Any liner used with a wood-burning appliance must be N2 class. For flexible steel liners under EN 1856-2, the condensate resistance is expressed as W (wet) for solid fuel use — the W designation indicates the liner is manufactured and tested for condensate service.
Polish Regulatory Requirements
In Poland, chimney relining is classified as a construction work requiring notification (zgłoszenie robót budowlanych) to the local Starostwo or, in Warsaw, the Wydział Architektury i Budownictwa. Relining a chimney in an apartment building (budynek wielorodzinny) requires consent from the building administrator (zarządca budynku) and may require a structural engineer's opinion if the existing chimney masonry is modified.
After relining, the chimney must be inspected by a chimney sweep holding at minimum a Klasa C certificate issued under the Polish master chimney sweep qualification system. The inspection verifies draw, tightness of joints, and liner position. Without this inspection and the associated protokół kominiarski document, the appliance cannot be insured or formally commissioned.
Related Articles
External references: PKN — EN 1457 and EN 1856 standards — GUNB — Polish construction authority