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House numbering is the system of giving a unique number to each building in a street or area, with the intention of making it easier to locate a particular building. The house number is often part of a postal address. The term describes the number of any building (residential or not) or vacant lot with a mailbox.
House numbering schemes vary by place, and in many cases even within cities. In some areas of the world, including many remote areas, houses are not numbered but named.
Australia and Oceania 
Australia and New Zealand 
In Australia and New Zealand, the current standard (Australia / New Zealand joint standard AS/NZS 4819:2003) for numbering newly created streets is to assign odd numbers to sites on the left and even numbers to the right when facing in the direction of increasing numbers (the European system). This standard came into force in 2003. Some exceptions exist where the road forms part of the boundary between different council areas or cities. For example, Underwood Road in Rochedale South has non-standard numbering, as it forms part of the boundary between Logan City and the city of Brisbane.
In New South Wales, the vast majority of streets were numbered before 2003 with odd numbers assigned to houses on the right of the street when facing in the direction of increasing numbers, and there is no plan to re-assign these numbers.
On some urban roads (e.g. Parramatta Road in Sydney) numbers will typically ascend until the road crosses a council or suburb boundary, then commence again at 1 or 2. Long roads can thus have several occurrences of each number. In semi-rural and rural areas, where houses and farms are widely spaced, a numbering system based on tens of metres or (less commonly) metres has been devised. Thus a farm 2300m from the start of the road, on the right-hand side would be numbered 230.
Hong Kong 
In Hong Kong, the British and European norm to number houses on one side of the street with odd numbers, and the other side with even numbers, is generally followed. Some roads or streets along the coastline may however have numbering only on one side, even if the opposite side is later reclaimed. These roads or streets include Ferry Street, Connaught Road West and Gloucester Road.
Japan and South Korea 
In Japan and South Korea, a city is divided into small numbered zones. The houses within each zone are then labelled in the order in which they were constructed, or clockwise around the block. This system is comparable to the system of sestieri (sixths) used in Venice.
Taiwan's "61, Alley 351, Lane 410, Gongguan St." allows direct navigation from Gongguan St., whereas in North America, one would need to know where the intervening, say, Jefferson Lane and Williams Alley, are.
The above navigation being: on Gongguan St. turn right the lane at house number 410, then left at the alley at house number 351, proceed to house number 61.
An example of the house numbering in rural area of Taiwan
In Europe the most common house numbering scheme is to number each plot on one side of the road with ascending odd numbers, from 1, and those on the other with ascending even numbers, from 2 or sometimes 0. The odd numbers are usually on the left side of the road, looking in the direction in which the numbers increase. Where additional buildings are inserted or subdivided, these are often suffixed a, b, etc. (in Spain and France, bis, ter, quater). Where buildings are later combined, they may use just one of the original numbers, combine them ("13/15"), or give their address as a range (e.g. "13–17"; not to be construed as including the even numbers 14 and 16). Where some plots are not built upon, there may be considerable gaps in the numbering scheme. If a lot of buildings are later built along a stretch of the street, either a range of unused numbers above the current highest house number may be used, introducing confusing discontinuities, or the remainder of the street must be renumbered.
In Venice, houses are numbered within districts known as sestieri, resulting in just six series for the entire city. In Genoa and in Florence houses are marked with black (sometimes also blue in Florence) numbers while businesses are usually (but not always) given red numbers, resulting in two distinct series for every street. The street numbers of businesses are denoted in writing (e.g., documents, online directories, etc.) by the addition of the letter "r" -- e.g., Via dei Servi 21r.
Double numbering 
The basic house number is the "old" or "descriptive number" (Czech popisné číslo, Slovak súpisné číslo). The descriptive number is unique within the municipal part (a village, a quarter, mostly for one cadastral area) or within a whole small municipality.
For makeshift and recreational buildings in the Czech Republic, "registration number" (evidenční číslo) from a separate number series is used instead of the descriptive number. Somewhere, this number begins with zero or with the letter "E" or has different colour to distinction or contains words like "nouzová stavba" (= makeshift structure), "chata" (= ca. weekend house) etc.
In some of settlements where streets have their names (mostly in cities), there are used also the "new" or "orientation numbers" (Czech orientační číslo, Slovak orientačné číslo) concurrently. The orientation numbers are arranged sequentially within the street or square. If the building is on a corner or has two sides, it can have two or more orientation numbers, one for each of the adjacent streets or squares. Solitary houses distant from named streets often have no orientation number. In some places, the name of a small quarter is used as a street name. If there is a new building between two older numbered ones, the orientation number is distinguished with an additional lower case letter (the sequence could be 5, 7, 9, 9a, 9b, 9c, 11, 13). In the 1930s–1950s in Brno, lower case letters were used for separate entrances of modern block houses perpendicular to the street.
Either number may be used in addresses. Sometimes, businesses will use both numbers to avoid confusion, usually putting the descriptive (or registration) number first: "Hlavní 20/7." The two (or three) types of numbers are commonly distinguished by colour of the sign. Each municipality can have its own traditional or official rules and colours. In Prague and many other Bohemian cities, descriptive numbers are red, orientation numbers are blue and "evidential" numbers are green or yellow or red. In many Bohemian municipalities, descriptive numbers are blue, black or are not unified. In Brno and some Moravian and Slovak cities, descriptive numbers are white-black signs, orientation numbers are red-white signs. Many cities and municipalities have different rules.
Formerly, Roman numerals signifying the city district were added to the description number: e.g. "125/III" means descriptive number 125 in district number III (in Prague, this was Malá Strana). Roman numerals were used both in cities and in village municipalities with more settlements. Nowadays, the name of the settlement is preferred instead of Roman numerals.
The first descriptive numbering was ordered by Maria Theresa in 1770 and implemented in 1770–1771. The series was given successively as the soldiers went through the settlement describing houses with numbers. Thereafter, every new house was allocated the next number sequentially, irrespective of its location. Most villages still use their original number series from 1770–1771. In cities, houses have been renumbered once or more often in order to be sequential – the first wave of renumbering came in 1805–1815. In 1857, the Austrian Emperor allowed a new system of numbering by streets. This new system was introduced in the biggest cities (Prague, Brno) in the 1860s. In 1884, land registration books were introduced and they used the old (description) numbers as a permanent and stable identifier of buildings. The new (orientation) numbers continue to be used concurrently.
The double numbering also existed in some Austrian cities.
Typical Prague combination: red descriptive number above, blue orientation number below
The city of Hostivice nearby Prague has blue descriptive numbers and red orientation numbers
Prčice, Central Bohemia. The descriptive number is blue, the orientation number negative blue.
In Prague-Chodov, both the old descriptive and the new orientation number are blue.
In Prague-Zbraslav both the old orientation and the new descriptive number are red
In Klikov, South Bohemia, most of house numbers are ceramic. Such villages use only descriptive numbers.
Yellow registration ("evidenční") number beginning with zero used instead of red. Prague-Komořany. The orientation number is blue.
Prague-Záběhlice, registration ("evidenční") number distinguished with green colour
Registration ("evidenční") number distinguished with the letter "E". Hradec Králové-Třebeš, Eastern Bohemia
Registration ("evidenční") number distinguished with words "provisorní stavba" (provisional structure). Prague-Hostivař.
Russia and former USSR countries 
In Russia and many other former USSR countries, the European style is generally used, with numbers starting from the end of the street closest to the town center. Buildings or plots at street intersections may be assigned a composite number, which includes the number along the intersecting street separated by a slash (Russian: дробь), like in Нахимова, 14/41 (14 is the number along Nakhimova street and 41 is the number along intersecting street).
The odd numbers are usually on the left side of the road, looking in the direction in which the numbers increase; though in some cities (including Saint Petersburg) the odd numbers are on the right side.
In some cities, especially hosting large scientific or military research centers in Soviet time, the numbering might be different: houses may have numbers related to the block rather than the street, thus 12-й квартал, дом 3 (Block 12, House 3), similar to the Japanese and Korean systems (see below). Aktau is one example of this.
When a numbered plot contains multiple buildings, they are assigned an additional component of the street address, called корпус (building), which is usually a sequentially assigned number unique within the plot (but sometimes contains letters as in 15а, 15б, 15в and so on). So, a Russian street address may look like Московское шоссе, дом 23, корпус 2 (Moscow Street, plot 23, building 2), or Льва Толстого, дом 14б (Leo Tolstoy Street, plot 14, building b).
On very long roads in suburban areas kilometer numbering system also may be used (like Australian rural numbering system). For example, 9-й км Воткинского шоссе (9th kilometer of Votkinsk Highway), and Шабердинский тракт, 7-й км (7th kilometer of Shaberdy Road).
Composite house numbers on street intersection, Veliky Novgorod
United Kingdom 
British houses started being numbered with the Postage Act of 1765. In many areas, particularly those in rural areas, many houses remain named but un-numbered. The odd numbers will typically, although not always, be on the left-hand side as seen from the centre of the town or village, with the lowest numbers at the end of the street closest to the town centre. Intermediate properties usually have a number suffixed A, B, C, etc., but there are several that have been given a half number, e.g. the old police station at 20½ Camberwell Church Street. At least one property (built next to no.2 after the street had been numbered) has been numbered zero.
Before the early/mid nineteenth century, it was common in England for numbering to proceed sequentially along one side of the road and then back down the other (in a similar way to "boustrephedon" writing). Subsequent changes to local numbering can present pitfalls to researchers using historic street directories, for instance.
This approach – numbering all plots on one side of a street consecutively, continuing clockwise back down on the opposite side of the street – still exists, for example in Pall Mall, culs-de-sac, streets with buildings only on one side, some new towns, and in many villages in Wales. For instance, 10 Downing Street, the official home of the First Lord of the Treasury (usually the Prime Minister), is next door to 11 Downing Street, the home of the Second Lord of the Treasury (usually the Chancellor of the Exchequer). Houses which surround squares are usually numbered consecutively clockwise.
Consecutive numbering is also used in some cases where only one side of the road is built up, as in Crayfield Road, Levenshulme, whose southern side is a former railway (now a cycle track).
Latin America 
Some[where?] countries in Latin America use systems similar to those in Europe. Houses are numbered in ascending order from downtown to the border of the city. In Mexico, the cities are usually divided in Colonias, which are small or medium areas. The colonia is commonly included in the address before the postal code. Sometimes when houses merge in a street or new constructions are built after the numbering was made, the address can become ambiguous. When a number is repeated a letter is added to the newest house. For example, if there are two 35's, one remains as 35 and the second one becomes 35A or 35Bis.
It is sometimes common that in remote towns or non-planned areas inside the cities that the streets do not have any name and the houses do not have numbers. In these cases the address of the houses are usually the name of the person or family, the name of the area or town, and "Dirección Conocida" (Known Address), which means that the house of the family is known by almost all the community. This kind of addressing is only used in remote towns or small communities near highways.
For people living near highways or roads the usual address is the kilometer of the road in which the house is established; if there's more than one, some references might be written or the "Dirección Conocida" may be added. In countries like Brazil and Argentina, but also in some villages in France, this scheme is used also for streets in cities, where the house number is the distance, measured in meters, from the house to the start of the street.
United States and Canada 
On most streets in the United States and Canada, odd numbers are on one side and even numbers on the other. Often, the number assigned is proportional to the distance from some baseline, so not all numbers are used. On very long roads, four- or five-digit addresses are common. In some places, such as Loudoun County, Virginia, almost all addresses contain five numbers.
In cities with a grid plan of streets, addresses often increase by 100 for each cross street, though in some cities they are consecutive within each block, so that a block where one side is numbered 501, 503, 505, 507, 509, 511 is followed by a block beginning with 601. Generally, within a single city there is a single base point used for all addresses; numbering of all streets therefore reflects its distance from that base point, and directionals (north, south, east, west) are used to refer to buildings on streets which run in that direction and are in that direction from the base point. Most cities start their numbering from the base point in either single-digits or at 100. For example, if an address is located six blocks north of a city's base point, it would likely be numbered in either the 600 or 700 range and often the designator "north" added to the street name. This is often omitted if the street does not cross beyond the base point or changes names when doing so.
In some cases, this base point may be theoretical, especially in the case of cities located on a coastline or otherwise having an irregular shape. For example, most of central and southern San Diego, California, as well as the suburb of La Mesa, is numbered from the theoretical intersection of First Street and Imperial Avenue; however, this location is actually in San Diego Bay, both streets ending at the waterfront several blocks away (with numbering in the 600s on (North) First and 1200s on (East) Imperial).
In the Phoenix Metropolitan Area, Arizona, addresses are coordinated in a grid. The origin of the addresses is the intersection of Central Avenue and Washington Street, in Phoenix. At this point, E. Washington St. goes out to the east, W. Washington St. goes out to the west, N. Central Ave. goes out to the north, and S. Central Ave. goes out to the south. The addresses increase outward from these "baselines." Even numbered addresses are always on the north and west sides of the roads, while odds are always on the south and east sides. Outward from Central Avenue, the North/south bound roadways are named as a numbered street or avenue. One block east of Central Avenue, is 1st Street. One block west of Central Avenue, is 1st Avenue. The numbers increase as one travels further east or west, away from Central Avenue. The grid allows for easy block/address locating, For example, the blocks between Central Avenue and 1st Avenue would be the 0 West Blocks. Likewise, the blocks between 5th Street and 6th Street would be the 500 East Blocks. East/west bound roadways in the Phoenix area are not named as consecutive numbers. Rather, they are named after notable landmarks or people. However, each block is still worth or assigned 100 addresses. Many cities in the area have long since modified their addresses to relate to Phoenix's baselines. For example, the lowest numbered avenue in Glendale is 43rd Avenue, as 43rd Avenue is the most easterly border that Glendale shares with Phoenix. Major roadways in Phoenix are near-exactly one mile apart. Formed intentionally, as these sites of major roads once were routes for irrigation lines that divided vast farmland into square miles. In most cases, major north/southbound roadways are 8 Avenues/Streets is a mile. In other words, 19th Avenue and 27th Avenue are 1 mile apart. There are some exceptions to this, but it is true in most cases. For instance, 7th Street and 7th Avenue, are one mile apart, although they are about 14 numbers apart. The grid allows for easy navigation. Baseline Road, despite its misleading name, is about 7600 S (76 blocks south of Washington Street.)
Addresses may also correlate with a street-numbering system. Thus, in Cleveland, Ohio, a building with the address 900 Euclid Avenue would be at the corner of Euclid Avenue and 9th Street. Similarly, in Philadelphia, a building whose address is "1610 Walnut Street" would be located on Walnut Street between 16th and 17th streets, more-or-less across the street from 1609. In San Diego, California, the numbered streets 28th-73rd were originally laid out farther apart than streets in the downtown business district (First-28th), and named streets later inserted in between; thus house numbering often increases by only 50 per block, as the hundreds numbers match the locations of the numbered streets, which alternate with named streets. In Queens, New York City, a so-called "Philadelphia Plan" uses a dash to separate the cross street number from the rest of the house number, as in 34-55 107th Street, which was once the home of Louis Armstrong.[vague]
San Francisco has several numbering systems in different districts; where these systems meet, parallel streets may be numbered in opposite directions. For example, the streets parallel to and east of Masonic Avenue are numbered northward, while Masonic and parallel streets to the west are numbered southward.
Along the Overseas Highway in the Florida Keys, house numbers indicate their distance from Mile Marker 0 in Key West. The mileage is found by dividing the house number by 1000 (for example, 77220 Overseas Highway is 77.2 miles from Mile Marker 0).
Buildings in many rural areas in the United States used to lack these kind of addresses. Instead, an old rural address might have been simply "Rural Route 3, Box 15." However, the adoption of 9-1-1 emergency systems has required the adoption of street names and house numbers in rural areas, typically numbering 1000 for each mile from the nearest town center.
In areas of rural Wisconsin, the address layout of many counties features a baseline in one corner of the county, with numbers increasing from that point and appended with a cardinal direction; for instance, an address on a north-south road 45 blocks north from the baseline is written as 'N4500', while an address 45 blocks west from the baseline on an east-west road is shown as 'W4500'. Some counties and suburban communities (such as Waukesha and the Town and City of Cedarburg) use a two-part address for both directions for easier referencing within a map and the numbering system (N4500-W4500 for instance).
Carmel-by-the-Sea, California lacks any house numbering whatsoever. Houses are referred to, instead, as (for example) "Junipero 3 SW of 10th", meaning "The third house on the west side of Junipero, south of 10th."[vague]
Block numbers 
Block numbers are a system of assigning numbers based on distance rather than strictly sequentially. Typically, each block is assigned 100 numbers, such that the building numbers on that block vary only in the last two digits. For example, in Washington, D.C., the block of 7th Street, N.W., between D and E streets, N.W., is designated as the 400 block, meaning that building numbers on that block are in the range from 400 to 499 inclusive. It is common to indicate block numbers on street signs.
Often, when numbered streets are used, the address numbers on perpendicular streets will use the number of the lower-numbered cross street as the "hundreds" portion of the number for each block.
Some localities, such as the Borough of Queens in New York City, use a block numbering system in which a hyphen separates the hundreds digit from the tens digit. For example, a building number that might elsewhere be written 16709 is instead written 167-09. In most cases, the first number refers to the street, avenue, drive, etc. where the numbering begins. For example 99-40 63rd Road is numbered because the starting point was 99th Street. Likewise, an address on a perpendicular block would have its number starting with 63-XX. In Queens (unlike other areas, such as Los Angeles, where one may see numbers such as 16700 Sunset Blvd.) rarely is the 00 number used to refer to an address, but rather the numbering starts at -01 or -02 depending on the side of the block.
Some localities in Utah and Wisconsin have a more elaborate system of block numbering. Such localities use compound block numbers to indicate the number of blocks from both the north-south and the east-west dividing lines. For example, an address in Utah might be of the form "226 N 3300 W" where other systems might use "226 33rd Ave NW". In this case, 226 N is the house number, and "3300 W" expresses the actual street name. Such an address is in the northwest quadrant of the addressing system. Another system, used in Wisconsin, might use "N112 W16709 Mequon Rd" rather than "16709 W. Mequon Rd". This numbering system is based on the southeast corner of each county and is based on a grid that will increase when traveling in a northerly or westerly direction using N and W, respectively. In Illinois, specifically in DuPage and Kane counties near Chicago, addresses in unincorporated and newly annexed areas are given according to their placement in a square mile section relative to downtown Chicago, specifically, the intersection of Madison St and State St. North-south streets use an address number beginning in N or S, and east-west streets use an address number beginning in W. The three-digit unique number that follows is assigned according to distance from the beginning of the quadrant. For example, "30W221 Butterfield Road" is in Naperville, 30 miles west of downtown Chicago. Addresses in adjoining suburban Cook County and Will County do not use this system, and instead use addresses that simply increase in number rather than have a letter such as "W" or "S" in the address. For example: "16701 South 96th Avenue" would be just south of 167th Street, and "9603 West 191st Street" would be just west of 96th Avenue.
- "Street Addressing Working Group and the National Street Addressing Standard". Intergovernmental Committee on Survey and Mapping. March 19, 2008. Retrieved February 24, 2010.
- 台灣的英文住址 Taiwan English postal addresses
- New York Times, July 16, 1898. http://query.nytimes.com/mem/archive-free/pdf?_r=2&res=9803EEDB1139E433A25755C1A9619C94699ED7CF&oref=slogin
- Related discussion, additional text.
- Bowlby, Chris. "Would you buy a number 13 house?". BBC News. December 12, 2008. Retrieved February 24, 2010.
- The Fanlight Number Company, July 19, 2009. http://www.fanlightnumbers.co.uk/history.html
- Navigating Utah's Streets - Salt Lake City
- Lincoln County Government - Merrill Wisconsin » Services » Rural Address Information
- History of DuPage County