Cladding is the application of one material over another to provide a skin or layer. In

construction Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and com ...

, cladding is used to provide a degree of

thermal insulation Thermal insulation is the reduction of heat transfer (i.e., the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with s ...

and

weather resistance Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...

, and to improve the appearance of buildings. Cladding can be made of any of a wide range of materials including wood, metal, brick,

vinyl Vinyl may refer to: Chemistry * Polyvinyl chloride (PVC), a particular vinyl polymer * Vinyl cation, a type of carbocation * Vinyl group, a broad class of organic molecules in chemistry * Vinyl polymer, a group of polymers derived from vinyl m ...

, and composite materials that can include aluminium, wood, blends of cement and recycled

polystyrene Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...

, wheat/rice straw fibres. Rainscreen cladding is a form of weather cladding designed to protect against the elements, but also offers thermal insulation. The cladding does not itself need to be

waterproof Waterproofing is the process of making an object or structure waterproof or water-resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environme ...

, merely a control element: it may serve only to direct water or wind safely away in order to control run-off and prevent its infiltration into the building structure. Cladding may also be a control element for noise, either entering or escaping. Cladding can become a fire risk by design or material.

Description

Cladding in construction is material applied over another to provide a skin or layer and used to provide a degree of

and

, and to improve the appearance of buildings. Between the cladding and the wall there is a cavity where rain can run down.

Design

Materials

Cladding can be made of any of a wide range of materials including wood, metal, brick,

, and composite materials that can include aluminium, wood, blends of cement and recycled

, or wheat/rice straw fibres. Materials used for cladding affect vulnerability to fire.

Purposes

Rainscreen cladding is a form of weather cladding designed to protect against the elements, but also offers thermal insulation. The cladding does not need, itself, to be

, merely a control element: it may serve only to direct water or wind safely away in order to control run-off and prevent its infiltration into the building structure. Single-skin metal panels are pre-formed wall panels made from metal that are one of the most commonly available types of cladding for industrial and commercial projects. Their high durability and easy installation make them ideal for low maintenance builds. Cladding may also be a control element for noise, either entering or escaping. Cladding applied to windows is often referred to as

window capping In construction, capping or window capping (window cladding, window wrapping) refers to the application of aluminum or vinyl sheeting cut and formed with a brake to fit over the exterior, wood trim of a building. The aluminum is intended to make a ...

and is a specialized field.

Vulnerability to building fires

Tower block with cladding exposed in Sheffield 2017

Between the cladding and the wall there is a cavity where rain can run down. In the event of a fire this draws hot air up like a

chimney A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typic ...

, intensifies the fire, and spreads it to the top of the clad area. The fire can then get inside the building through open windows, for example to curtains blowing through windows. In addition to the chimney effect, the cladding material itself can contribute to a fire. Brick has excellent fire resistance; planks or

weatherboard Clapboard (), also called bevel siding, lap siding, and weatherboard, with regional variation in the definition of these terms, is wooden siding of a building in the form of horizontal boards, often overlapping. ''Clapboard'' in modern Americ ...

s made from

fibre cement Fibre cement is a composite building and construction material, used mainly in roofing and facade products because of its strength and durability. One common use is in fiber cement siding on buildings. Material description The term "cement" ori ...

or steel have high fire resistance;

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

and reconstituted timber products have good fire resistance, and timber weatherboards and

plywood Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another. It is an engineered wood from the family of manufactured ...

sheets have poor fire resistance. Composite cladding typically consists of panels thick made of a core material sandwiched between two aluminium faces. The core material may be

polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including bo ...

(which is

combustible A combustible material is something that can burn (i.e., ''combust'') in air. A combustible material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable mat ...

), a mineral-based material, or a combination of both. Panels of the same appearance may have different core materials; those with a higher proportion of mineral core withstand fire better, but can still be considered combustible. Fire will be spread ''by'' the cladding if the core is combustible. In the wake of the

Grenfell Tower fire On 14 June 2017, a high-rise fire broke out in the 24-storey Grenfell Tower block of flats in North Kensington, West London, at 00:54 BST and burned for 60 hours. 72 people died, two later in hospital, with more than 70 injured and 223 escapin ...

London London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a majo ...

, and similar fires in

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

Dubai Dubai (, ; ar, دبي, translit=Dubayy, , ) is the most populous city in the United Arab Emirates (UAE) and the capital of the Emirate of Dubai, the most populated of the 7 emirates of the United Arab Emirates.The Government and Politics of ...

, and elsewhere, great attention has been paid to the

fire protection Fire protection is the study and practice of mitigating the unwanted effects of potentially destructive fires. It involves the study of the behaviour, compartmentalisation, suppression and investigation of fire and its related emergencies, as we ...

qualities of cladding used in tower-blocks and similar high-rise multiple-occupancy housing and, in particular, the use of

aluminium composite material A sandwich panel is any structure made of three layers: a low-density core ( PIR, mineral wool, XPS), and a thin skin-layer bonded to each side. Sandwich panels are used in applications where a combination of high structural rigidity and low ...

(ACM) and ACM panels (ACP). Grenfell Tower was clad with composite panels with a polyethylene core which contributed to the fire; these panels cost about £2 less than ones with incombustible core. There are estimated to be about 600 high-rise blocks of flats in the UK that have "similar" cladding and some fire safety tests—not full BS 8414 tests—were carried out on panels; of the first 75 tested, 100% failed. Updated as information becomes available.

References