House numbering

A numbered house in Germany.

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.

House numbering schemes vary by place, and in many cases even within cities. In some, usually remote, areas of the world, houses are not numbered at all, instead simply being named.

Asia

Japan and Korea use a system where the city is divided into small sections each with its own numeric code. The houses within that zone are then labelled based on the order in which they were constructed. This system is comparable to the 'sestriere,' or district, system of Venice.

Australia

In Australia, most addresses follow the European scheme (odd numbers on one side, even on the other). On very long 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 rural areas, where houses and farms are widely spaced, a numbering system based on tenths of kilometres has been devised. Thus a farm 2.3km from the start of the road would be numbered 23, with odds and evens defined as above. [1]

Europe

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, bis, ter). Where buildings are later combined, they may use just one of the original numbers, or give their address as a range (e.g. 13‑15). Note that in this example, this range includes numbers 13 and 15, and does not include number 14. Where some plots are not built upon, there may be considerable gaps in the numbering scheme.

In Britain the even numbers will typically, although not always, be on the lefthand side as one moves in a direction away from the centre of the town or village, with lower numbers at the end of the street closest to the town centre or town hall.

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 cul de sacs, streets with buildings only on one side and in many Welsh villages. For instance, 10 Downing Street, the official home of the First Lord of the Treasury, is next door to 11 Downing Street, the home of the Chancellor of the Exchequer.

Houses which surround squares are usually numbered consecutively clockwise.

In Venice, Italy houses are numbered by district, resulting in just six series for the entire city; in Florence houses are given black numbers and businesses red numbers, resulting in just two series.

In Prague and other Czech cities, two numbering systems are used concurrently. Buildings display both a číslo popisné (descriptive number) in red and a číslo orientační (orientation number) in blue. The red number is unique to the building in its section of town and may not be concurrent with addresses of nearby buildings. The blue number is a simple sequential number, similar to the house numbers used in other European cities. Either number may be used in addresses. Sometimes, businesses will use both numbers to avoid confusion, putting the red number first: "Hlavní 20 / 7."

In Sweden, there is also a system (fastighetsbeteckningar) numbering farms and thereby also the houses on them. The numbering is done per village. When a farm is split, either composited numbers (like 2:1 and 2:2) are made to be able differ the farms, or a completely new number, previously unused, can be given to one or both of the farms.

North America

In much of North America, buildings are not numbered according to a simple sequence but rather according to distance from a given baseline. As a result, four- and five-digit addresses are common. Odd numbers are typically on one side of the street, evens on the other.

In cities with a grid pattern of streets, addresses often increase by 100 for each cross 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.

In San Francisco, parallel streets will sometimes be numbered in opposite directions. As an example, Broderick Street numbers ascend from south to north, while Masonic Avenue, just three blocks away, ascends from north to south.

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 dropping the last three digits in the address (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.

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."

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 two least significant 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; for instance, the article on Pennsylvania Avenue shows a street sign indicating what is probably the most famous block number in the world.

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.

Some localities in the Midwest 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 might be of the form "N112 W16709 Such-and-such Street" rather than "16709 W. Such-and-such Street." Such an address is in the northwest quadrant of the addressing system.