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Lime-ash floors were an economic form of floor construction from the 15th century to the 19th century, for upper floors in parts of England where
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...
or
chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Cha ...
were easily available. They were strong, flexible, and offered good heat and
sound insulation Soundproofing is any means of impeding sound propagation. There are several basic approaches to reducing sound: increasing the distance between source and receiver, decoupling, using noise barriers to reflect or absorb the energy of the sound w ...
.


History

Lime-ash is the residue found at the bottom of a wood-fired
lime kiln A lime kiln is a kiln used for the calcination of limestone ( calcium carbonate) to produce the form of lime called quicklime ( calcium oxide). The chemical equation for this reaction is : CaCO3 + heat → CaO + CO2 This reaction can take ...
, consisting of waste lime and wood ash. These kilns became common in the early 15th century and continued to be used until newer technology replaced them in the late 19th century. Lime-ash could also be made in coal-fired kilns. In areas where gypsum was common they were known as plaster floors. Lime ash was used on the upper floors of yeomen's houses and in great houses such as
Hardwick Hall Hardwick Hall in Derbyshire is an architecturally significant country house from the Elizabethan era, a leading example of the Elizabethan prodigy house. Built between 1590 and 1597 for Bess of Hardwick, it was designed by the architect Ro ...
in Derbyshire, where the upper surface would be buffed to a fine finish using a mixture of egg-white, curdled milk and fish-gelatine. The underside could be left bare or smoothed with a lime-plaster. Alternatively the floor joist could be concealed with a conventional lath and plaster ceiling. Isaac Ware in his ''A Complete Body of Architecture (1756)'' remarks on "the beauty of floors of plaster mixed with other ingredients", comparing them with those of granite.


Construction

A lime-ash floor typically occurs on the upper floors of a building. One can expect to find construction beams lying the length of the building with flooring
joist A joist is a horizontal structural member used in framing to span an open space, often between beams that subsequently transfer loads to vertical members. When incorporated into a floor framing system, joists serve to provide stiffness to the su ...
s being placed across at intervals of about 400 mm (16 in). A bed of reeds (or similar grasses) is placed on the joists making a tight thatch. They are secured by placing oak laths over them and nailing these to the joists. A 50 mm slurry of ''lime-ash composition'' is poured over the bedding material which supports it until the lime-ash has dried out. The reed bed acts as shuttering and laths add to the rigidity of the floor. However laths that are too tightly fixed to the joists hinder the movement the floor must have to cope with settlement and the structural changes during its lifetime which can be counted in centuries. The lime-ash composition varies according to the materials locally available: *
Lime Lime commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Botany ...
 – acts as a binder and contains particles of raw limestone and over burnt lime. * Fuel ash – this pozzolanic material binds its constituent Si(OH)4 with the Ca² ions in a
pozzolanic reaction The pozzolanic activity is a measure for the degree of reaction over time or the reaction rate between a pozzolan and Ca2+ or calcium hydroxide (Ca(OH)2) in the presence of water. The rate of the pozzolanic reaction is dependent on the intrinsic ...
. It contains burnt wood or coal. *
Gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywa ...
, to help with set *
Clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay parti ...
with fragments of broken brick and tile, another pozzolanic material *
Silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
or sand, which acts as an aggregate * Other debris – vegetable or animal and bubbles of air. Nigel and Mary Kerr in ''Lincolnshire Life'', November 1987, write: "A traditional mix used in Nottinghamshire, Northamptonshire and south Lincolnshire was: 'One third lime, one third well sifted coal ashes and one third loamy clay and horse dung from grasses. They add that ox blood and horse hair were sometimes included.


Problems occurring

After long use the surface can start to break up: this can be ignored, or a further
screed Screed has three meanings in building construction: # A flat board (screed board, floating screed) or a purpose-made aluminium tool used to smooth and to "true" materials like concrete, stucco and plaster after they have been placed on a surface ...
of lime-ash composition can be laid over the original floor. This was often done in the past but does increase the weight of the structure. Damp can cause fungi to rot the bedding material, or insects to gnaw away the laths and indeed the joists, taking with it the floor. Knocking through service ducts without due care can destroy the floor, as can overloading due to change of use or addition of partition walls.


Laying a new floor

Lime-ash is generally no longer available, so repairs and reconstruction are usually done using a mixture of lime putty, coal ash, Gypsum (Class A hemi hydrate fine casting plaster), unburnt loamy clay and burnt crushed tile. To this are added retardants such as
Keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, hor ...
(natural) or
Sodium Citrate Sodium citrate may refer to any of the sodium salts of citric acid (though most commonly the third): * Monosodium citrate * Disodium citrate * Trisodium citrate The three forms of salt are collectively known by the E number E331. Applications ...
(manufactured). The bedding material is repaired with water reed , or combed
winter wheat Winter wheat (usually ''Triticum aestivum'') are strains of wheat that are planted in the autumn to germinate and develop into young plants that remain in the vegetative phase during the winter and resume growth in early spring. Classification ...
which is the strongest form of straw, and chestnut laths which can be obtained in lengths.


Geographical variations

They can be found principally in Derbyshire, Cheshire, Shropshire, Herefordshire and the Welsh borders, Staffordshire, Leicestershire, Worcestershire and Warwickshire; Lincolnshire, Nottinghamshire and many parts of Yorkshire. Some floors are made almost entirely of gypsum, particularly around Newark – plaster floors would be a better description.


Buildings

* Little Morton Hall, Cheshire * Barlborough Old Hall, Derbyshire *
Hardwick Hall Hardwick Hall in Derbyshire is an architecturally significant country house from the Elizabethan era, a leading example of the Elizabethan prodigy house. Built between 1590 and 1597 for Bess of Hardwick, it was designed by the architect Ro ...
, Derbyshire * Newton's house at Woolsthorpe, Lincolnshire *
Gainsborough Old Hall Gainsborough Old Hall in Gainsborough, Lincolnshire is over five hundred years old and one of the best preserved medieval manor houses in England. The hall was built by Sir Thomas Burgh in 1460. The Burghs were rich, flamboyant and powerful. Gai ...


See also

*
Cob (material) Cob, cobb, or clom (in Wales) is a natural building material made from subsoil, water, fibrous organic material (typically straw), and sometimes lime. The contents of subsoil vary, and if it does not contain the right mixture, it can be modified ...
*
Rammed earth Rammed earth is a technique for constructing foundations, floors, and walls using compacted natural raw materials such as earth, chalk, lime, or gravel. It is an ancient method that has been revived recently as a sustainable building method. ...
* Straw-bale construction


References


Bibliography

* * {{refend Floors Recycled building materials Sustainable building Sustainable technologies