This document specifies calculations for the dimensioning of Kachelgrundöfen/Putzgrundöfen (tiled/mortared stoves) based upon the required nominal heat output of the stove as declared by the producer. The Kachelgrundöfen/Putzgrundöfen (tiled/mortared stoves) are of individual one-off construction design. The document can be used for log wood fired Kachelöfen (tiled stoves) that burn one fuel load per storage period with a maximum load between 10 kg and 40 kg (log wood with water content from 12 % to 20 %, thickness of 5 cm to 10 cm in diameter, length varies usually from 25 cm to 50 cm, and is oriented toward the combustion chamber dimensions) and a storage period (nominal heating time) between 8 h and 24 h. This document is valid for Kachelgrundöfen/Putzgrundöfen (tiled/mortared stoves) equipped with fireclay as interior material, with an apparent density between 1,750 kg/m3 and 2,300 kg/m3, a degree of porosity from 17 % up to 33 % by volume and a heat conductivity from 0,90 W/mK up to 1,30 W/mK (temperature range 20 °C to 400 °C). This document is valid for Kachelgrundöfen/Putzgrundöfen (tiled/mortared stoves) with combustion air supply from the side via a heating door frame or the standing grate of the heating door into the combustion chamber. The document is valid for an inflow speed of the combustion air between 2 m/s and 4 m/s. This document also applies to the combination with combustion chambers that are suitable for one-off Kachelgrundöfen/Putzgrundöfen (tiled/mortared stoves) and for which compliance with the legally required emission values has been verified as part of a type test by an accredited and/or notified body. This document is applicable to combustion chambers: " with an air-fuel ratio of between 1,95 and 3,95 according to the type test; " with a maximum fuel less than 10 kg, but more than 5 kg; " using other suitable materials as well as fireclay. With regard to the type test, this document is applicable combustion chambers which are: " from slow heat release appliances tested according to EN 15250 (or prEN 16510-2-5); " inserts tested according to EN 13229 (or prEN 16510-2-2); or " combustion chambers tested according to respective national standards (e.g. ÖNORM B 8303). This document applies to type tested combustion chambers designed for batch fired pellet burning if meeting the requirements according to this document (air-fuel ratio between 1.95 and 3,95, the load of the pellets shall be burned in 78 ± 20 min). This document is not valid for combinations with water heat exchangers for central heating or other heat absorbing elements like open water tanks and glass plates greater than 1/5 of the combustion chamber surface, etc. This document is not valid for mass-produced prefabricated stoves (slow heat release appliances) or partly prefabricated stoves (slow heat release appliances) according to EN 15250.