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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 c ...
s in cold and temperate climates. Such roofs are built with mostly
timber Lumber is wood that has been processed into uniform and useful sizes (dimensional lumber), including beams and planks or boards. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, window frames). ...
, take a number of different shapes, and are covered with a variety of
materials A 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 ge ...
.


Overview

Modern timber roofs are mostly framed with pairs of common rafters or prefabricated wooden trusses fastened together with truss connector plates. 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 eac ...
es. Roofs are also designated as ''warm'' or ''cold roof'' depending on the way they are designed and built with regard to thermal
building insulation Building insulation is material used in a building (specifically the building envelope) to reduce the flow of thermal energy. While the majority of insulation in buildings is for thermal insulation, thermal purposes, the term also applies to ...
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 *** Respirator, 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 inst ...
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 List of roof shapes, sloped roofs. The slope of a roof is properly known as its Roof pitch, pitch and flat roofs have up to approximately 10°. Flat roofs are an anci ...
s actually slope up to approximately ten degrees to shed water. Flat roofs on houses are primarily found in
arid Aridity is the condition of geographical regions which make up approximately 43% of total global available land area, characterized by low annual precipitation, increased temperatures, and limited water availability.Perez-Aguilar, L. Y., Plata ...
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 ant ...
or
hurricane A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its ...
may make landfall, the main
engineering Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...
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 thr ...
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 typical ...
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 O ...
. 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 Beam (structure), steel beams that extend from the ridge or hip to the wall plate, downslope perimeter or eave, and that are designed to support the roof Roof shingle, shingles, ...
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 m ...
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. P ...
s are fixed to the rafters; or boards,
plywood Plywood is a composite material manufactured from thin layers, or "plies", of wood veneer that have been stacked and glued together. It is an engineered wood from the family of manufactured boards, which include plywood, medium-density fibreboa ...
, or
oriented strand board Oriented strand board (OSB) is a type of engineered wood, 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. OSB may have a rough and ...
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 serves a decorative purpose. There are various types of walls, including border barriers between countries, brick wal ...
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 mechanical load (more generally a force) applied to Structural engineering#Structural elements, structural elements. A load causes stress (physics), stress, deformation (engineering), deformation, displa ...
'' 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 construction objects such as buildings and non-building structures. Buildings must conform to the code to obtain planning permis ...
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 shingles, but some have other types of
roof shingle A roof’s 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 joint ...
s or
metal roof A metal roof is a roofing system featuring metal pieces or tiles exhibiting corrosion resistance, impermeability to water, and long life. It is a component of the building envelope. The metal pieces may be a covering on a structural, non-waterpro ...
s.
Tile Tiles are usually thin, square or rectangular coverings manufactured from hard-wearing material such as ceramic, Rock (geology), stone, metal, baked clay, or even glass. They are generally fixed in place in an array to cover roofs, floors, wal ...
and
thatch Thatching is the craft of building a roof with dry vegetation such as straw, Phragmites, water reed, Cyperaceae, sedge (''Cladium mariscus''), Juncus, rushes, Calluna, heather, or palm branches, layering the vegetation so as to shed water away fr ...
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. 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 ...
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 (expanding foam in the UK) is a chemical product used in construction and engineering primarily as Building insulation, insulation and as a filler material. It is produced as a liquid but quickly expands and hardens into a stiff, ligh ...
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 () is a transcontinental region around the Eastern Mediterranean encompassing the historical Fertile Crescent, the Levant, Anatolia, Egypt, Mesopotamia, and coastal areas of the Arabian Peninsula. The term was invented in the 20th ...
, 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), 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 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'' or ''papyruses'') can a ...
, palm fronds and
tree bark Bark is the outermost layer 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'' 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. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...
,
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 Dictionar ...
, crushed potsherds and
straw Straw is an agricultural byproduct consisting of the dry wikt:stalk, stalks of cereal plants after the grain and chaff have been removed. It makes up about half of the crop yield, yield by weight of cereal crops such as barley, oats, rice, ry ...
. This type of roofing material is well-equipped to withstand wetness and rain downpours. In
Sanaa Sanaa, officially the Sanaa Municipality, is the ''de jure'' capital and largest city of Yemen. The city is the capital of the Sanaa Governorate, but is not part of the governorate, as it forms a separate administrative unit. At an elevation ...
,
Yemen Yemen, officially the Republic of Yemen, is a country in West Asia. Located in South Arabia, southern Arabia, it borders Saudi Arabia to Saudi Arabia–Yemen border, the north, Oman to Oman–Yemen border, the northeast, the south-eastern part ...
, 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 () was a region of Western Europe first clearly described by the Roman people, Romans, encompassing present-day France, Belgium, Luxembourg, and parts of Switzerland, the Netherlands, Germany, and Northern Italy. It covered an area of . Ac ...
,
Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
,
Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...
and
Aquitaine Aquitaine (, ; ; ; ; Poitevin-Saintongeais: ''Aguiéne''), archaic Guyenne or Guienne (), is a historical region of southwestern France and a former Regions of France, administrative region. Since 1 January 2016 it has been part of the administ ...
, 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 herpes zoster or zona, 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. T ...
or thatched. The
Colchians In classical antiquity and Greco-Roman geography, Colchis (; ) was an exonym for the Georgian polity of Egrisi ( ka, ეგრისი) located on the eastern coast of the Black Sea, centered in present-day western Georgia. Its population, the ...
in Pontus made their roofs by "cutting away the ends of crossbeams, and ymaking 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, HEN or Hens may also refer to: Places Norway *Hen, Buskerud, a village in R ...
cover it with leaves and mud." In
Marseilles Marseille (; ; see below) is a city in southern France, the prefecture of the department of Bouches-du-Rhône and of the Provence-Alpes-Côte d'Azur region. Situated in the Provence region, it is located on the coast of the Mediterranean S ...
, 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. Ancient Greek authors used "Phrygian" as an umbrella term t ...
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 26th parallel south, 26° and all of the Northern Territory. Those local government areas of Western Australia and Q ...
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, also called ferroconcrete or ferro-concrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ...
block wall. This system is typically in place every around
perimeter A perimeter is the length of a closed boundary that encompasses, surrounds, or outlines either a two-dimensional shape or a one-dimensional line. The perimeter of a circle or an ellipse is called its circumference. Calculating the perimet ...


See also

*
Dropped ceiling A dropped ceiling is a secondary ceiling, hung below the main (structural) ceiling. It may also be referred to as a drop ceiling, T-bar ceiling, false ceiling, suspended ceiling, grid ceiling, drop in ceiling, drop out ceiling, or ceiling tile ...
*
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 hip roof, hipped roof with steeply pitched slopes rising to a peak.W. Dean EastmanHometown Handbook: Architecture./ref> Tented roofs, a hallmark of medieval religious archite ...
*
Building construction Construction are processes involved in delivering buildings, infrastructure, industrial facilities, and associated activities through to the end of their life. It typically starts with planning, financing, and design that continues until the a ...
*
Building envelope A building envelope or building enclosure 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 ...
* 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 encompass a broad range of designs, including flat (or shed roof, shed), gabled, hip roof, hipped, arched, domed, and a wide variety of other configurations An essential aspect of roof design is the roof angle or roof pitch, pitch, w ...
*
Metal Roofing Alliance 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 through marketing, education and selective action on public policies that affect metal ...
* Roof cleaning * Roofer * Roofing felt * Tensile architecture * Thin-shell structure * Pahuichi


References


External links

* {{Authority control Roof construction Structural system