chemistry

Parapet

Parapet is a chemistry 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 Parapet rather than just read about it. In short: A parapet is a barrier that is an upward extension of a wall at the edge of a roof, terrace, balcony, walkway or other structure. The word derives from the Italian parapetto (parare 'to cover/defend' and petto 'chest/breast').

Key takeaways

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

Reference excerpt

A parapet is a barrier that is an upward extension of a wall at the edge of a roof, terrace, balcony, walkway or other structure. The word derives from the Italian parapetto (parare 'to cover/defend' and petto 'chest/breast'). Where extending above a roof, a parapet may simply be the portion of an exterior wall that continues above the edge line of the roof surface, or may be a continuation of a vertical feature beneath the roof such as a fire wall or party wall. Parapets were originally used to defend buildings from military attack, but today they are primarily used as guard rails, to conceal rooftop equipment, reduce wind loads on the roof, and to prevent the spread of fires.

Parapet types Parapets may be plain, embattled, perforated or panelled, which are not mutually exclusive terms.

Plain parapets are upward extensions of the wall, sometimes with a coping at the top and corbel below. Embattled parapets may be panelled, but are pierced, if not purely as stylistic device, for the discharge of defensive projectiles. Perforated parapets are pierced in various designs such as circles, trefoils, or quatrefoils. Panelled parapets are ornamented by a series of panels, either oblong or square, and more or less enriched, but not perforated. These are common in the Decorated and Perpendicular periods.

Historic parapet walls

The Mirror Wall at Sigiriya, Sri Lanka built between 477 and 495 AD is one of the few surviving protective parapet walls from antiquity. Built onto the side of Sigiriya Rock it ran for a distance of approximately 250 meters (270 yards) and provided protection from inclement weather. Only about 100 meters (110 yards) of this wall exists today, but brick debris and grooves on the rock face along the western side of the rock clearly show where the rest of this wall once stood.

Parapet roofs

Parapets surrounding roofs are common in London. This dates from the Building Act 1707 which banned projecting wooden eaves in the cities of Westminster and London as a fire risk. Instead an 18-inch brick parapet was required, with the roof set behind. This was continued in many Georgian houses, as it gave the appearance of a flat roof which accorded with the desire for classical proportions. In Shilpa Shastras, the ancient Indian science of sculpture, a parapet is known as hāra. It is optionally added while constructing a temple. The hāra can be decorated with various miniature pavilions, according to the Kāmikāgama. In the Bible the Hebrews are obligated to build a parapet on the roof of their houses to prevent people falling (Deuteronomy 22:8).

Firewall parapets Many firewalls are required to have a parapet, a portion of the wall extending above the roof. The parapet is required to be as fire resistant as the lower wall, and extend a distance prescribed by building code.

Bridge parapets

Parapets on bridges and other highway structures (such as retaining walls) prevent users from falling off where there is a drop. They may also be meant to restrict views, to prevent rubbish passing below, and to act as noise barriers. Bridge parapets may be made from any material, but structural steel, aluminium, timber and reinforced concrete are common. They may be of solid or framed construction. In European standards, parapets are defined as a sub-category of "vehicle restraint systems" or "pedestrian restraint systems".

Parapets in fortification

A parapet fortification (known as a breastwork when temporary) is a wall of stone, wood or earth on the outer edge of a defensive wall or trench, which shelters the defenders. In medieval castles, they were often crenellated. In later artillery forts, parapets tend to be higher and thicker. They could be provided with embrasures for the fort's guns to fire through, and a banquette or fire-step so that defending infantry could shoot over the top. The top of the parapet often slopes towards the enemy to enable the defenders to shoot downwards; this incline is called the superior talus.

See also Attic style Baluster Merlon Redoubt

References

Bibliography Senani Ponnamperuma (2013). The Story of Sigiriya. Panique Pty Ltd. pp. 124–127, 179. ISBN 978-0987345141.

External links

Victorian Forts glossary Archived 2016-03-04 at the Wayback Machine Parapet What is a Parapet? Archived 2009-02-01 at the Wayback Machine

Illustrations

Worked examples

Example 1 — a first encounter with Parapet

Start with the simplest possible case. Write down what Parapet claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, 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 Parapet 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 Parapet 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 Parapet

In research: Parapet appears in chemistry 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 Parapet 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: Parapet is common in secondary-school and first-year university syllabi. It links to neighbouring topics Architectural elements, Bridge components, Castle architecture, so understanding it makes those chapters shorter.
In everyday life: Look for Parapet 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Parapet in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Parapet 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 Parapet out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Parapet in simple terms?

Why does Parapet matter?

Because it connects several chemistry 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 Parapet?

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 Parapet.