Royal Hospital Dublin

According to the Oxford English Dictionary, ‘Chimney’ originally meant a fireplace.  It is thought to be derived from the Latin Caminus that meant furnace, forge or oven.  During the Middle English it was called ‘Chimenee’.  Known as chimney stalks with a cluster of stalks called a stack.  The chimney pots were a superstructure that sat atop the stack.  Chimneys have been an especially important part of buildings for centuries especially in these colder climates where there is a need to retain heat but remove smoke or to prevent downdrafts.  It is difficult to understand how some early chimneys were made from wood, how appropriate that the practice was outlawed by early fire prevention laws!  Valentine Fletcher coined the word ‘Caminology’ as the study of chimneys.  There are various chimney designs featured on this site. [i]

During the 13th century chimneys were produced of clay or tin in Britain.  They were known as ‘cans’ in Scotland also as ‘tuns’ in South West Britain.  The purpose of the chimney was to increase the speed with which smoke rose upwards by reducing the size of the outlet.  The reduction of opening size prevented the entrance of rain or a downdraft of air that prevent the smoke leaving the building or the scatter of hot embers from the fire.  The openings, called pockets, grills, horns or louvres in a pot prevented cross drafts on the top end, they also served to increase the smoke’s flow upwards.  Pots were ‘flanched’ or flaunched in place on the stack for prevention of mortar or cement sloping inwards towards the pot.  Clay pots usually were produced as terracotta red, terracotta buff or salt glaze.  The latter type of pot produced weatherproof pots that also prolonged its life as the silica in the clay combined with the sodium in the salt formed a glazing coating of sodium silicate.  The Chimney Pot Museum at Longport, Stoke – on – Trent has a collection of over 2,500 pots.  During 1964 the National Clay Foundation catalogued approximately five hundred chimney designs.  Several had exotic names ie. Smoke Cure, Champion, Weemac or Spiral Captain. [ii]

For the Victorians, the chimneys were ornamental or a source of aesthetic pleasure.  Their Georgian ancestors had not placed much emphasis on chimneys.  Thus, the Victorians created ornate soaring objects that pleased them.  The chimneys on detached or semi – detached houses often formed part of the formal symmetry of a building.  In a terraced or row of houses built to a similar design they offered an aesthetically pleasing or regular rhythm.  Victorian personal taste focused on the fireplace as the centre of their homes.  This was apparent in the various designs or quality of the pots.  Vast arrays of claywear pots were available at that era rather than the previous rather crude versions of the late 18th Century.  This site provides various images. [iii]

Prior to the construction of Irish cottages during the 1700’s inhabitants resided in round hut style dwellings built of wattle or daub but had no outlet for smoke extraction.  The materials used later for cottages were sourced within a five-mile radius of site.  Those homes had no foundations but were trenches filled with clay, stores or mud were used for support.  The floors were made from compacted clay or mud or in some region’s even flagstones.  Roof construction varied in regions with barged gables in the Midlands while in North – Western areas fully gabled walls were the norm.  In most area thatch roofs were constructed with weathen or oaten straw or materials of rushes, marram grass, heather or flax.  In rocky area like the Burren slate or stone may have been in use.  In fact, another less attractive roof covering was corrugated iron. The fireplace or hearth was usually centred in the main room of the house.  Usually fireplaces were made from stone, wattle or daub.  The hearth wall was very deep, it extended to the ceiling with the Chimney stack protruding further through the cottage roof.  The use of fuel necessitated stone flues to protect from chimney fires.  Range fireplaces emerged during the 1880’s. [iv]

Chimneys pots made an appearance during the reign of George 111.  In several Castles or Tower Houses the flues were simple openings in the parapet.  The role of the pot was fulfilled by slates or tiles set on edge in a bed of mortar.  Many of the early chimneys were shallow boxes formed from wattle & plaster that rose just above the roof.  It was during the second half of the 19th century before they became fashionable.  The inside of the flues was generally paraged or plastered until the end of the 19th century when ceramic liners became available.  There may have been a hood produced to exhale smoke over a turf fire.  The original pots were made from cast iron, but the most popular type were vitrified clay ones.  The Hearth Tax plus the change to fuel influenced the designs of the chimneys.  From that time pots were built with more durable materials of brick or stone. [v]

Several old house chimneys served a hearth on each floor with multiple flues that snaked through offsets within the masonry.  Well-built chimneys were parged with mortar to line the flue with clay tiles the standard liner since the 1900’s.  Clay flue tiles were round or rectangular ceramic units 24” tall stacked to make a liner with mortared joints.  Stainless steel flue liners are manufacture in flexible or rigid forms in a variety of alloys & designs.  Rigid flue liners are available in diameters from 3 – 10 while flexible corrugated metal tubes are 2 – 10 in diameter.  On this site are illustrations by Michael Crotiner with a photo by Paul Rocheleau. [vi]

The pumice liner system comes in a range of 15 diameters from 150m to 1000 mm internal diameter.  Theses pumice liners are used in masonry chimneys where the linings are surrounded by bricks, stones or blocks of 100mm.  Installation is required to agree with building regulations.  There are fifteen flue sizes available that have lengths of 600 m to 1000 m with fewer joints.  On this site are several sketches of various designs. [vii]

Basic extraction from fires in eons past were a hole in the ceiling of dwellings.  Industrial Chimneys were created to draw smoke by the Romans in their bakeries.  Domestic chimneys appeared during the 12th century within Europe.  Ordinary dwellings would have had chimneys produced from mud, wood or plaster. Later bricks were placed around liners.  Chimney pots or venting caps were placed on top to control downdrafts.  During the Middle Ages in Western Europe the design of crow – stepped gables allowed maintenance access to the chimney tops of Castles or Manor Houses.  The production of ventilation shafts produced with clay, metal or masonry isolated the hot toxic exhaust smoke or gases from fireplaces.  Vertical Chimneys drew air in the combustion known as stack to ensure smooth flow of gases.  There are several photos on this link including one by Gaudi in Barcelona. (Jan 2021) [viii]


This publication ‘Chimney Pots and Stacks’ 1968 Fletcher Valentine is believed to have been the first specialized book on the subject. [ix]

This is an Irish publication; ‘Béaloideas Hearth and Chimney in the Irish House’ Ó Danachair Caoimhín June – December 1946 Pages 91 – 107 An Cumann le Béaloideas Éireann / Folklore of Ireland, one may read a preview or download at this link;

One may view several chimney pots at this link:

This site has an image from Dublin by Mark Sawyer:

On this site it states that there Open Flues are known as Conventional Flues (CF) while Closed Flues are Balanced Flues (F B) or Fanned Flues ( F F.) (Chrishutt 8th December 2005):


[i] Chimney Stacks & Pots ( (assessed 12th September 2020)

[ii] Chimney Stacks & Pots ( (assessed 12th September 2020)

[iii] Chimneys ( (assessed 12th September 2020)

[iv] Irish Cottage History ( (assessed 12th September 2020)

[v] Traditional Buildings ( (assessed 12th September 2020)

[vi] Old House Repairs ( [assessed 5th January 2021]

[vii] Pumice Systems ( [assessed 5th January 2021]

[viii] Chimney ( [assessed 5th January 2021]

[ix] Chimney Stacks & Pots ( (assessed 12th September 2020)


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