engineering

Lime-ash floor

Lime-ash floor is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lime-ash floor rather than just read about it. In short: 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 or chalk were easily available. They were strong, flexible, and offered good heat and sound insulation.

Key takeaways

Lime-ash floor belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Lime-ash floor to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lime-ash floor from memory before moving on to harder problems.

Reference excerpt

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 or chalk were easily available. They were strong, flexible, and offered good heat and sound insulation.

History Lime-ash is the residue found at the bottom of a wood-fired lime kiln, 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 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 joists 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 – 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. It contains burnt wood or coal. Gypsum, to help with set Clay with fragments of broken brick and tile, another pozzolanic material Silica 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 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 (natural) or sodium citrate (manufactured). The bedding material is repaired with water reed 5 feet (1,500 mm), or combed winter wheat which is the strongest form of straw, and chestnut laths which can be obtained in 4 feet (1,200 mm) 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, Derbyshire Newton's house at Woolsthorpe, Lincolnshire Gainsborough Old Hall

See also Cob (material) Rammed earth Straw-bale construction

References

Bibliography

Worked examples

Example 1 — a first encounter with Lime-ash floor

Start with the simplest possible case. Write down what Lime-ash floor claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lime-ash floor before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lime-ash floor ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lime-ash floor

In research: Lime-ash floor appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lime-ash floor in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lime-ash floor is common in secondary-school and first-year university syllabi. It links to neighbouring topics Floors, Recycled building materials, Sustainable building, so understanding it makes those chapters shorter.
In everyday life: Look for Lime-ash floor outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Lime-ash floor in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lime-ash floor means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lime-ash floor out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lime-ash floor in simple terms?

Why does Lime-ash floor matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lime-ash floor?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lime-ash floor.