Basement

However, the use of basements depends largely on factors specific to a particular geographical area such as climate, soil, seismic activity, building technology, and real estate economics.

Basements in small buildings such as single-family detached houses are rare in wet climates such as Great Britain and Ireland where flooding can be a problem, though they may be used in larger structures.

Their use may be restricted in earthquake zones, because of the possibility of the upper floors collapsing into the basement; on the other hand, they may be required in tornado-prone areas as a shelter against violent winds.

Subbasements are even more susceptible to flooding and water damage than basements and are therefore rare, except in dry climates and at higher elevations.

A cellar is intended to remain at a constant cool (not freezing) temperature all year round and usually has either a small window/opening or some form of air ventilation (air/draught bricks, etc.)

In the United Kingdom, almost all new homes built since the 1960s have no cellar or basement due to the extra cost of digging down further into the sub-soil and a requirement for much deeper foundations and waterproof tanking.

For this reason, especially where lofts have been converted into living space, people tend to use garages for the storage of food freezers, tools, bicycles, garden and outdoor equipment.

However, full basements are commonplace in new houses in the Canadian and American Midwest and other areas subject to tornado activity or requiring foundations below the frost line.

An underground crawl space (as the name implies) is a type of basement in which one cannot stand up—the height may be as little as one foot (30 cm), and the surface is often soil.

Care must be taken in doing so, however, as water from the damp ground, water vapour (entering from crawl space vents), and moisture seeping through porous concrete can create a perfect environment for mold/mildew to form on any surface in the crawl space, especially cardboard boxes, wood floors and surfaces, drywall and some types of insulation.

Mould spores, decomposition odours, and material from dust mites in the crawl space can come up with the air, aggravating asthma and other breathing problems, and creating a variety of health concerns.

[citation needed] Dry rot and other conditions detrimental to buildings (particularly wood and timber structures) can develop in enclosed spaces.

Such vents are usually fitted with metal grating, mesh, or louvers which can block the movement of rodents and vermin but generally not insects such as termites and carpenter ants.

In places with oddly stratified soil substrata or high water tables, such as most of Florida, Texas, Oklahoma, Arkansas, and areas within 50 miles (80 km) of the Gulf of Mexico, basements are usually not financially feasible unless the building is a large apartment or commercial structure.

Some designs elect to simply leave a crawl space under the house, rather than a full basement due to structural challenges.

For large office or apartment buildings in prime locations, the cost of land may justify multi-storey basement parking garages.

Even if unfinished and unoccupied, basements are heated in order to ensure relative warmth of the floor above, and to prevent water supply pipes, drains, etc.

In Canada, the walls of a finished basement are typically insulated to the floor with vapor barriers to prevent moisture transmission.

However, a finished basement should avoid wood or wood-laminate flooring, and metal framing and other moisture resistant products should be used.

Health Canada advocates the use of special radon gas traps for floor drains that lead to soil or to a sealed sump pump.

Even with functioning sump pumps or low water tables, basements may become wet after rainfall, due to improper drainage.

One usually finds within it a water heater, various pipes running along the ceiling and downwards to the floor, and sometimes a workbench, a freezer or refrigerator, or a laundry set (usually found in older homes).

Boxes of various materials, and objects unneeded in the rest of the house, are also often stored there; in this regard, the unfinished basement takes the place both of the cellar and of the attic.

In this case the space has been designed, either during construction or at a later point by the owners, to function as a fully habitable addition to the house.

The main point of distinction between this type of basement and the two others lies in its being either entirely unmodified (unlike the finished basement) beyond the addition of furniture, recreational objects and appliances, and/or exercise equipment on the bare floor, or slightly modified through the installation (besides any or all of the aforementioned items) of loose carpet and perhaps simple light fixtures.

In both cases, the objects found there—many of which could be found in a finished basement as well—might include the following: weight sets and other exercise equipment; the boom boxes or entertainment systems used during exercise; musical instruments (which are not in storage, as they would technically be in an unfinished basement; an assembled drum set would be the most easily identified of these); football tables, chairs, couches and entertainment appliances of lesser quality than those in the rest of the house; refrigerators, stand-alone freezers, and microwaves (the first and the second being also sometimes used as supplementary storage units in an unfinished basement); and sports pennants and/or other types of posters which are attached to the walls.

It is also common to have a secondary (or primary) home office in a partially finished basement, as well as a workbench and/or a space for laundry appliances.

In London the construction of finished retrofit basements is big business with a large number of projects in the 100–200 square meter bracket.

[20] Hospitals often place their nuclear chemistry and radiation therapy and diagnostic resources in basements to utilize the shielding from the earth.

In Canada, historically the basement area was excluded from advertised square footage of a house as it was not part of the living space.