Roofing Material
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Domestic roof construction is the framing and roof covering which is found on most detached
house A house is a single-unit residential building. It may range in complexity from a rudimentary hut to a complex structure of wood, masonry, concrete or other material, outfitted with plumbing, electrical, and heating, ventilation, and air condi ...
s in cold and temperate climates. Such roofs are built with mostly
timber Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, wi ...
, take a number of different
shapes A shape or figure is a graphical representation of an object or its external boundary, outline, or external surface, as opposed to other properties such as color, texture, or material type. A plane shape or plane figure is constrained to lie on ...
, and are covered with a variety of
materials Material is a substance or mixture of substances that constitutes an object. Materials can be pure or impure, living or non-living matter. Materials can be classified on the basis of their physical and chemical properties, or on their geologic ...
.


Overview

Modern timber roofs are mostly framed with pairs of common rafters or prefabricated wooden trusses fastened together with
truss connector plate A truss connector plate, or gang plate, is a kind of tie. Truss plates are light gauge metal plates used to connect prefabricated light frame wood trusses. They are produced by punching light gauge galvanized steel to create teeth on one side. ...
s. Timber framed and historic buildings may be framed with principal rafters or
timber roof truss A timber roof truss is a structural framework of timbers designed to bridge the space above a room and to provide support for a roof. Trusses usually occur at regular intervals, linked by longitudinal timbers such as purlins. The space between each ...
es. Roofs are also designated as ''warm'' or ''cold roof'' depending on how they are designed and built with regard to thermal
building insulation Building insulation is any object in a building used as insulation for thermal management. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insul ...
and
ventilation Ventilation may refer to: * Ventilation (physiology), the movement of air between the environment and the lungs via inhalation and exhalation ** Mechanical ventilation, in medicine, using artificial methods to assist breathing *** Ventilator, a ma ...
. The steepness or
roof pitch Roof pitch is the steepness of a roof expressed as a ratio of inch(es) rise per horizontal foot (or their metric equivalent), or as the angle in degrees its surface deviates from the horizontal. A flat roof has a pitch of zero in either insta ...
of a sloped roof is determined primarily by the roof covering material and aesthetic design.
Flat roof A flat roof is a roof which is almost level in contrast to the many types of sloped roofs. The slope of a roof is properly known as its pitch and flat roofs have up to approximately 10°. Flat roofs are an ancient form mostly used in arid c ...
s actually slope up to approximately ten degrees to shed water. Flat roofs on houses are primarily found in
arid A region is arid when it severely lacks available water, to the extent of hindering or preventing the growth and development of plant and animal life. Regions with arid climates tend to lack vegetation and are called xeric or desertic. Most ar ...
regions. In high wind areas, such as where a
cyclone In meteorology, a cyclone () is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above (opposite to an anti ...
or
hurricane A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...
may make landfall, the main
engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...
consideration is to hold the roof down during severe storms. Every component of the roof, as of course the rest of the structure, has to withstand the uplift forces of high wind speeds. This is accomplished by using metal ties fastened to each rafter or truss. This is not normally a problem in areas not prone to high wind or extreme weather conditions. In the UK, a concrete tiled roof would normally have rafters at centers, roof battens at centers and ceiling joists at centers. The United States still uses
imperial units The imperial system of units, imperial system or imperial units (also known as British Imperial or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed thro ...
of measurement and framing members are typically spaced sixteen or twenty-four inches apart. The roof framing may be interrupted for openings such as 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 ...
or
skylight A skylight (sometimes called a rooflight) is a light-permitting structure or window, usually made of transparent or translucent glass, that forms all or part of the roof space of a building for daylighting and ventilation purposes. History Open ...
. Chimneys are typically built with a water diverter known as a ''cricket'' or ''saddle'' above the chimney. Flashing is used to seal the gap between the chimney and roofing material.


Construction of a rafter roof

A simple rafter roof consists of
rafter A rafter is one of a series of sloped structural members such as wooden beams that extend from the ridge or hip to the wall plate, downslope perimeter or eave, and that are designed to support the roof shingles, roof deck and its associated ...
s that the ''rafter foot'' rest on horizontal
wall plate A plate or wall plate is a horizontal, structural, load-bearing member in wooden building framing. Timber framing A plate in timber framing is "A piece of Timber upon which some considerable weight is framed...Hence Ground-Plate...Window-plat ...
s on top of each wall. The top ends of the rafters often meet at a ''ridge beam'', but may butt directly to another rafter to form a pair of rafters called a ''couple''. Depending on the roof covering material, either horizontal
lath A lath or slat is a thin, narrow strip of straight-grained wood used under roof shingles or tiles, on lath and plaster walls and ceilings to hold plaster, and in lattice and trellis work. ''Lath'' has expanded to mean any type of backing mate ...
s,
batten A batten is most commonly a strip of solid material, historically wood but can also be of plastic, metal, or fiberglass. Battens are variously used in construction, sailing, and other fields. In the lighting industry, battens refer to linea ...
s, or
purlin A purlin (or historically purline, purloyne, purling, perling) is a longitudinal, horizontal, structural member in a roof. In traditional timber framing there are three basic types of purlin: purlin plate, principal purlin, and common purlin. Pu ...
s are fixed to the rafters; or boards,
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 ...
, or
oriented strand board Oriented strand board (OSB) is a type of engineered wood similar to particle board, formed by adding adhesives and then compressing layers of wood strands (flakes) in specific orientations. It was invented by Armin Elmendorf in California in 1963. ...
form the ''roof deck'' (also called the sheeting or sheathing) to support the roof covering. Heavier ''under purlins'' or ''purlin plates'' are used to support longer rafter spans. Tie beams, which may also serve as ceiling joists, are typically connected between the lower ends of opposite rafters to prevent them from spreading and forcing the walls apart.
Collar beam A collar beam or collar is a horizontal member between two rafters and is very common in domestic roof construction. Often a collar is structural but they may be used simply to frame a ceiling. A collar beam is often called a collar tie but this ...
s or collar ties may be fixed higher up between opposite rafters for extra strength. The rafters, tie beams and plates serve to transmit the weight of the roof to the
wall A wall is a structure and a surface that defines an area; carries a load; provides security, shelter, or soundproofing; or, is decorative. There are many kinds of walls, including: * Walls in buildings that form a fundamental part of the supe ...
s of the building


Construction of a truss roof

Pre-manufactured roof trusses come in a wide variety of styles. They are designed by the manufacturer for each specific building. Timber trusses also are built in a variety of styles using wood or metal joints. Heavy timber rafters typically spaced to apart are called ''principal rafters''. Principal rafters may be mixed with ''common rafters'' or carry ''common purlins''.


Design loads

Roof framing must be designed to hold up a ''
structural load A structural load or structural action is a force, deformation, or acceleration applied to structural elements. A load causes stress, deformation, and displacement in a structure. Structural analysis, a discipline in engineering, analyzes the ef ...
'' including what is called ''dead load'', its own weight and the weight of the roof covering, and additional loading called the ''environmental load'' such as snow and wind. Flat roofs may also need to be designed for ''live loads'' if people can walk on them. In the United States,
building code A building code (also building control or building regulations) is a set of rules that specify the standards for constructed objects such as buildings and non-building structures. Buildings must conform to the code to obtain planning permission ...
s specify the loads in pounds per square foot which vary by region. The load and ''span'' (distance between supports) defines the size and spacing of the rafters and trusses.


Roof covering

The roofing material, including underlayment and roof covering, is primarily designed to shed water. The covering is also a major element of the architecture, so roofing materials come in a wide variety of colors and textures. The primary roof covering on houses in North America are
asphalt shingle An asphalt shingle is a type of wall or roof shingle that uses asphalt for waterproofing. It is one of the most widely used roofing covers in North America because it has a relatively inexpensive up-front cost and is fairly simple to install. ...
s, but some have other types of
roof shingle Roof shingles are a roof covering consisting of individual overlapping elements. These elements are typically flat, rectangular shapes laid in courses from the bottom edge of the roof up, with each successive course overlapping the joints below. ...
s or
metal roof A metal roof is a roofing system made from metal pieces or tiles characterized by its high resistance, impermeability and longevity. It is a component of the building envelope. Zinc, copper and steel alloys are commonly used. History Copper has pla ...
s.
Tile Tiles are usually thin, square or rectangular coverings manufactured from hard-wearing material such as ceramic, stone, metal, baked clay, or even glass. They are generally fixed in place in an array to cover roofs, floors, walls, edges, or o ...
and
thatch Thatching is the craft of building a roof with dry vegetation such as straw, water reed, sedge (''Cladium mariscus''), rushes, heather, or palm branches, layering the vegetation so as to shed water away from the inner roof. Since the bulk of ...
roofs are more common in Europe than North America. Some roofing materials help reduce air conditioning costs in hot climates by being designed to reflect light. Asphalt shingles is the most used roofing material in North America, making up as much as 75% of all steep slope roofs. This type of material is also gaining popularity in Europe due to lower installation costs. Asphalt shingles dominate the North American residential roofing market, because they are typically less expensive compared to other materials. In the southern US and Mexico, clay tile roofs are also very popular, due to their longevity, and ability to withstand hurricane winds with minimal or no damage. In Europe, slate and tile roofs are very popular. Many slate roofs in Europe are over 100 years old, and typically require minimal maintenance / repairs.


Ventilation and insulation

Roof space ventilation is needed to regulate the temperature within the roof space. Without proper ventilation, humidity can cause interstitial condensation within the roof fabric; this can lead to serious structural damage, wet or dry rot, and can ruin insulation. Condensation within the roof space is much more of a problem today due to: much less fortuitous ventilation due to tighter building envelopes with high performance windows and door and no chimneys leading. This tighter envelope means the air temperature in buildings has risen, the warmer the air in the building is, the more water vapour the air can carry. As the occupied part of the building has become warmer, the roof space has become colder, with high performance insulation and roofing membranes leading to a cold roof space. When the warm, moist air from below rises into the cold roof space; condensation begins as the air temperature drops to the ‘dew point’ or as the warm air comes into contact with any of the cold surfaces in the roof. Most building materials are permeable to water vapour; brick, concrete, plaster, wood and insulation all can fall victim to
interstitial condensation Interstitial condensation is a type of condensation that may occur within an enclosed wall, roof or floor cavity structure, which can create dampening. When moisture-laden air at dew point temperature penetrates inside a cavity of the structure, ...
, this is why UK Building Regulations require roofs to be ventilated, either by the use of soffit vents, ridge vents, or replacement ventilation slates or tiles. Ventilation of the roof deck speeds the evaporation of water from leakage or
condensation Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor to ...
and removes heat which helps prevent ice dams and helps asphalt shingles last longer. Building codes in the U.S. specify ventilation rates as a minimum of of opening per (1:150) with a ratio of 1:300 in some conditions. Warm air rises, so ceiling insulation is designed to have a higher r-value and the insulation is often installed between the ceiling joists or rafters. A properly insulated and ventilated roof is called a ''cold roof''. A ''warm roof'' is a roof that is not ventilated, where the insulation is placed in line with the roof pitch. A ''hot roof'' is a roof designed not to have any ventilation and has enough air-impermeable insulation in contact with the sheathing to prevent condensation such as when
spray foam Spray foam is a chemical product created by two materials, isocyanate and polyol resin, which react when mixed with each other and expand up to 30-60 times its liquid volume after it is sprayed in place. This expansion makes it useful as a specia ...
insulation is applied directly to the under-side or top-side of the roof deck or in some cathedral ceilings. A more recent design is the installation of a roof deck with foil-backed foam along with a second deck that is air-gapped away from the foil-backed foam to allow air to flow vertically to a ventilation outlet at the peak of the roof—it is a double-deck design with an air gap. This design improves efficiency.


Primitive roofing techniques

In the
Near East The ''Near East''; he, המזרח הקרוב; arc, ܕܢܚܐ ܩܪܒ; fa, خاور نزدیک, Xāvar-e nazdik; tr, Yakın Doğu is a geographical term which roughly encompasses a transcontinental region in Western Asia, that was once the hist ...
, from Roman times, throughout the Middle Ages and up to the start of the 20th-century, roofs of houses were constructed in the following manner: They first arranged the wooden rafters over the walls, at a distance of about 60 cm. between each rafter; over which rafters they laid down horizontally thin strips of wood, or boards (
purlins A purlin (or historically purline, purloyne, purling, perling) is a longitudinal, horizontal, structural member in a roof. In traditional timber framing there are three basic types of purlin: purlin plate, principal purlin, and common purlin. Pu ...
), in close proximity to each other, each board having a thickness of 3 finger-breadths (6.75 cm), or a little less. Over these boards they then firmly secured in place a matting material made of natural plant fibers woven together, such as cane reeds, leaves of
rush Rush(es) may refer to: Places United States * Rush, Colorado * Rush, Kentucky * Rush, New York * Rush City, Minnesota * Rush Creek (Kishwaukee River tributary), Illinois * Rush Creek (Marin County, California), a stream * Rush Creek (Mono Cou ...
or
papyrus Papyrus ( ) is a material similar to thick paper that was used in ancient times as a writing surface. It was made from the pith of the papyrus plant, '' Cyperus papyrus'', a wetland sedge. ''Papyrus'' (plural: ''papyri'') can also refer to a ...
, palm fronds and
tree bark Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines, and shrubs. Bark refers to all the tissues outside the vascular cambium and is a nontechnical term. It overlays the wood and consist ...
., s.v. ''
Kelim A kilim ( az, Kilim کیلیم; tr, Kilim; tm, Kilim; fa, گلیم ''Gilīm'') is a flat tapestry-woven carpet or rug traditionally produced in countries of the former Persian Empire, including Iran, the Balkans and the Turkic countries. Kil ...
'' 20:5
Over this matting material they first placed a thick layer of clay, followed by a layer of soil having a thickness of , after which they daubed the top with a clay aggregate consisting of a cement mixture of
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 par ...
,
rubble Rubble is broken stone, of irregular size, shape and texture; undressed especially as a filling-in. Rubble naturally found in the soil is known also as 'brash' (compare cornbrash)."Rubble" def. 2., "Brash n. 2. def. 1. ''Oxford English Dictionary ...
, crushed potsherds and
straw Straw is an agricultural byproduct consisting of the dry stalks of cereal plants after the grain and chaff have been removed. It makes up about half of the yield of cereal crops such as barley, oats, rice, rye and wheat. It has a number ...
. This type of roofing material is well-equipped to withstand wetness and rain downpours. In
Sanaa Sanaa ( ar, صَنْعَاء, ' , Yemeni Arabic: ; Old South Arabian: 𐩮𐩬𐩲𐩥 ''Ṣnʿw''), also spelled Sana'a or Sana, is the capital and largest city in Yemen and the centre of Sanaa Governorate. The city is not part of the Governo ...
,
Yemen Yemen (; ar, ٱلْيَمَن, al-Yaman), officially the Republic of Yemen,, ) is a country in Western Asia. It is situated on the southern end of the Arabian Peninsula, and borders Saudi Arabia to the Saudi Arabia–Yemen border, north and ...
, in the early 20th-century, twisted mats of palm-leaves were laid over wooden beams used to support the ceilings. These mats were held in place by wooden sticks laid at right angles to the beams. Above these crossing sticks, bushes were spread, and these were again covered with mats. The wooden beams and the mats were overlaid with a very hard lime or mortar coating. The thickness of the ceiling-wall seldom exceeded , excluding the beams. In ancient
Gaul Gaul ( la, Gallia) was a region of Western Europe first described by the Romans. It was inhabited by Celtic and Aquitani tribes, encompassing present-day France, Belgium, Luxembourg, most of Switzerland, parts of Northern Italy (only during ...
,
Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...
,
Portugal Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...
and
Aquitaine Aquitaine ( , , ; oc, Aquitània ; eu, Akitania; Poitevin-Saintongeais: ''Aguiéne''), archaic Guyenne or Guienne ( oc, Guiana), is a historical region of southwestern France and a former administrative region of the country. Since 1 January ...
, houses were constructed with peaked roofs daubed with lumps of dried mud and covered with reeds and leaves, while other roofs made with oak
shingles Shingles, also known as zoster or herpes zoster, is a viral disease characterized by a painful skin rash with blisters in a localized area. Typically the rash occurs in a single, wide mark either on the left or right side of the body or face. ...
or thatched. The
Colchians In Greco-Roman geography, Colchis (; ) was an exonym for the Georgian polity of Egrisi ( ka, ეგრისი) located on the coast of the Black Sea, centered in present-day western Georgia. Its population, the Colchians are generally though ...
in Pontus made their roofs by "cutting away the ends of crossbeams, and making them converge gradually as they lay them across, they bring them up to the top from the four sides in the shape of a pyramid. They
hen Hen commonly refers to a female animal: a female chicken, other gallinaceous bird, any type of bird in general, or a lobster. It is also a slang term for a woman. Hen or Hens may also refer to: Places Norway *Hen, Buskerud, a village in Ringer ...
cover it with leaves and mud." In
Marseilles Marseille ( , , ; also spelled in English as Marseilles; oc, Marselha ) is the prefecture of the French department of Bouches-du-Rhône and capital of the Provence-Alpes-Côte d'Azur region. Situated in the camargue region of southern Franc ...
, during classical antiquity, tiles were not used on the roofs of houses, but rather only earth mixed with straw. The ancient
Phrygians The Phrygians (Greek: Φρύγες, ''Phruges'' or ''Phryges'') were an ancient Indo-European speaking people, who inhabited central-western Anatolia (modern-day Turkey) in antiquity. They were related to the Greeks. Ancient Greek authors used ...
built a pyramidal roof of logs fastened together, and covering them over with reeds and brushwood, upon which was heaped up very high mounds of earth.


Gallery

File:大工と屋根造作・垂木構造P8020029.jpg, A steeply pitched, timber framed roof under construction in Japan File:Hrebenova vaznice.jpg, A heavy ridge beam and rafters. A tie or joist visible in foreground File:Trusses LeBlanc Construction.jpg, A set of trusses placed atop a home under construction File:FEMA - 1135 -Project Impact principles - roof reinforcements.jpg, A strongly reinforced roof structure in a cyclone-prone area File:Custom-orb.jpg, Applying corrugated iron sheeting to a house under construction. Shows two gables and external cyclonic fastenings File:Oklahoma-roofing-contractors.jpg , Example of architectural roof designs File:Hip-roof.jpg, A hip roof construction in
Northern Australia The unofficial geographic term Northern Australia includes those parts of Queensland and Western Australia north of latitude 26° and all of the Northern Territory. Those local government areas of Western Australia and Queensland that lie p ...
showing multinail truss construction. The blue pieces are roll formed metal roof battens or purlins. This roof is built with purpose-made steel hook bracket which is bolted to the truss with M16 bolt. The bracket is bolted to an M16 bolt cast in situ, embedded into the
reinforced concrete Reinforced concrete (RC), also called reinforced cement concrete (RCC) and ferroconcrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having hig ...
block wall. This system is typically in place every around
perimeter A perimeter is a closed path that encompasses, surrounds, or outlines either a two dimensional shape or a one-dimensional length. The perimeter of a circle or an ellipse is called its circumference. Calculating the perimeter has several pract ...


See also

* Interior protection *
Roof garden A roof garden is a garden on the roof of a building. Besides the decorative benefit, roof plantings may provide food, temperature control, hydrological benefits, architectural enhancement, habitats or corridors for wildlife, recreational oppo ...
*
Tented roof A tented roof (also known as a pavilion roof) is a type of polygonal hipped roof with steeply pitched slopes rising to a peak. W. Dean EastmanHometown Handbook: Architecture./ref> Tented roofs, a hallmark of medieval religious architecture, wer ...
*
Building 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 ...
*
Building envelope A building envelope is the physical separator between the conditioned and unconditioned environment of a building including the resistance to air, water, heat, light, and noiseSyed, Asif. ''Advanced building technologies for sustainability''. Hoboke ...
* Copper roofing *
Green roof A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage ...
*
List of roof shapes Roof shapes include flat (or shed), gabled, hipped, arched, domed, and a wide variety of other configurations detailed below. Roof angles are an integral component of roof shape, and vary from almost flat to steeply pitched. Roof shapes diffe ...
*
Metal Roofing Alliance The Metal Roofing Alliance (MRA) was formed by the Metal Construction Association The Metal Construction Association (MCA) is an industry organization in the US that was formed in 1984 with a focus on expanding the use of metal in construction th ...
*
Roof cleaning Roof cleaning is the process of removing algae, mold, mildew, lichen and moss from roofs. Also cleaning oxidation on metal roofs. Cleaning can extend the duration of a roof's ability to function. Algae and other types of build-up often form on t ...
*
Roofer A roofer, roof mechanic, or roofing contractor is a tradesperson who specializes in roof construction. Roofers replace, repair, and install the roofs of buildings, using a variety of materials, including shingles, bitumen, and metal. Roofin ...
*
Roofing felt Bituminous waterproofing systems are designed to protect residential and commercial buildings. Bitumen (asphalt or coal-tar pitch) is a mixed substance made up of organic liquids that are highly sticky, viscous, and waterproof. These systems ar ...
*
Tensile architecture A tensile structure is a construction of elements carrying only tension and no compression or bending. The term ''tensile'' should not be confused with tensegrity, which is a structural form with both tension and compression elements. Tensile st ...
* Thin-shell structure *
Pachuichi ''Pahuichi'', sometimes spelled ''pagüichi'', is a term of uncertain origin used in the Spanish of Bolivia and northern Argentina to refer to a rustic domiciliary structure with a roof made of straw or dried palm fronds. History of use The pri ...


References


External links

* {{Authority control Roofs Construction Structural system