Cloaks And Claddings For Buildings

The term 'cladding' refers to components that are attached to the primary structure of a building to form non-structural, external surfaces. This is as opposed to buildings in which the external surfaces are formed by structural elements, such as masonry walls, or applied surfaces such as render. While the least important structurally, sometimes the most important step in finishing a building construction project is the outer skin. These coverings, known as cloaks, cladding's, and/or facades, can be a welcome sight when selected and applied correctly, or a dangerous eyesore otherwise. 

Whilst cladding is generally attached to the structure of the building, it typically does not contribute to its stability. However, cladding does play a structural role, transferring wind loads, impact loads, snow loads and its own self-weight back to the structural framework. In particular, wind causes positive and negative pressure on the surface of buildings and cladding must have sufficient strength and stiffness to resist this load, both in terms of the type of cladding selected and its connections back to the structure.

Beautiful Skin, Not Too Deep
An important finishing step in building construction is to apply cladding materials as an exterior skin or facade. While these materials may improve building aesthetics they can also function to control environmental elements such as air, temperature, water, and light. Improperly selected or placed they can also become a hazard, such as striped glass panels in high wind or falling masonry siding during earthquakes. It becomes important then to choose cladding treatments with proper consideration to function, aesthetics, cost, and environment.

Choices And Then Some
Although the available selection of specific materials is quite large they can be collected into several broad categories:

One of the most diverse materials, wood cladding may consist of natural or sawn products such as clapboards, shingles, and planks; composites such as plywoods, chipboards, and fiberboards; and veneers. Natural wood products typically are more demanding to install and maintain but can lend a more desirable appearance in certain cases. Composite wood has greater installation flexibility but typically requires a finishing layer of paint, veneer, or resin. Veneers are rarely used but can affect the look of natural, rare, and/or exotic wood while avoiding excessive consumption. Wood products in general are considered sustainable, durable, and weather resistant. They will also require greater maintenance for appearance and resistance to damage by insects.

Natural stone is one of the oldest types of this cladding material. There are also fired masonry products such as brick and tiles, cast materials such as stucco, concrete blocks and panels, and veneers of brick and stone. Masonry products typically have high initial material and installation costs but also comprise some of the most durable and low maintenance selections available.

Thin skins of aluminum, steel, and copper are the typical materials used for cladding. No longer limited to corrugated products there are also molded panels, shingles, trims, and of course gutters and flashing produced from these metals. While also low maintenance and durable these skins tend to be initially expensive and more vulnerable to damage from hail or wind blown projectiles.

One of the most visually diverse products, this category includes tiles and panels made of fired ceramic clays. Just as in pottery, various dyes, glazes, and finishes can be combined in an almost infinite display of color and patterns. Quality ceramic materials are also very durable and almost maintenance free. These properties also dictate higher material and installation costs, however, and are typically reserved for commercial buildings.

Traditionally used for windows and window walls, glass used as cladding lends a dramatic, modern look to buildings. Available as hardened glass tiles and panels but also as an even tougher laminate “sandwich" of metal, colorizing layers, and glass. Again, very durable and low maintenance but with higher material and installation costs.

The thinnest cladding skins of all consisting of paints, spray applied coatings, and molded or extruded panels. With almost endless colorizing schemes available along with toughening fillers and additives, paints have become much more durable and versatile compared to the original whitewash. While costs have risen as a result, paint is still the most cost effective cladding available today. Slightly thicker and longer lasting are spray applied coatings such as epoxies and low VOC urethane's, although cost is higher as well. Finally, extruded or molded polymer panels are one of the most cost effective cladding materials in this category. Vinyl siding is perhaps the most well known example but others are available as well such as ABS and poly carbonate. Longer lasting and more attractive than earlier products, polymers have a good sustainability rating due to their recycling potential.

Finally, almost all the materials in the previous categories can be combined into composite products to lower weight, increase insulation ratings, and improve versatility. Exterior Insulation and Finish Systems (EIFS), insulated concrete forms, expanded foam core vinyl, laminates, and many other combinations are available as cost effective additions to the listing. Even high tech combinations are becoming available like photo voltaic panels and color changing tiles.

The Importance of Being Tenacious: Application Systems & Fasteners
Even the best cladding material becomes worth less and even dangerous if the connection system employed is not appropriate to the application. In seismic zones where buildings must be designed to flex the cladding fastening system must be able to take the excess movement as well. Hurricane and other high wind areas require applications that can withstand the extraordinary air pressure changes during these weather events. Flying panes of glass and falling concrete panels are not items the Civil Engineer wants to see on the news. Or anyone else, for that matter. But designed and installed correctly, cloaks and cladding's are usually a welcome finishing touch to building construction.

When selecting or designing a suitable cladding, designers should pay particular attention to:
  1. Design detailing.
  2. Control of air leakage.
  3. Control of condensation.
  4. Integrity and continuity of Insulation.
  5. Prevention of water penetration, or provision of drainage.
  6. Control of thermal movement.
  7. Spread of fire.
  8. Ease of installation.
  9. External attachments and fixings.
  10. Cleaning.
  11. Maintenance, remedial work and renewal.
  12. Resilience, strength and durability.
High-quality, well-designed, properly-installed cladding can help maximise thermal performance, minimise air leakage, and optimise natural daylighting. This can help reduce the need for mechanical and electrical building services, and so improve energy efficiency and lower capital and running costs. Poor design detailing or installation may compromise cladding performance and can result in safety problems such as cladding collapse or cladding panels pulling away from the structure.

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