Sprung floor

A sprung floor is a floor that absorbs shocks giving it a softer feel. Such floors are considered the best available for dance and indoor sports and physical education.They enhance performance and greatly reduce injuries. Modern sprung floors are supported by foam backing or rubber feet, while the traditional floors are cushioned mechanically. Many dance halls with sprung hard wood floors date back to the early 20th century, such as the Willowbrook Ballroom in Chicago (1921) and the Crystal Ballroom in Portland, OR (1914).

This article deals mainly with the basic requirements and construction of sprung floors. See performance surface for more on customization for different activities.

Terminology

A sprung floor is also sometimes referred to as a floating floor. That term though more often refers to a floor that insulates against noise or a raised floor with ducts and wires underneath as in computer halls.

The top layer of a sprung floor is a performance surface. In dance this may be replaceable to suit different styles, such surfaces are often also called marley floors or dance floors. Here the term "floor surface" or just "surface" is used for this.

A sprung floor excluding the surface is often referred to as the "sub-floor", though this may also refer to the concrete or other floor under a sprung floor.

The term "speed" refers to the traction (kinetic friction) of performance surfaces: "fast" describes slippery surface, and "slow" higher-traction surface, like a gym floor.

Requirements

The basic requirements for a sports floor or a dance floor are the same. They should encourage optimum performance and be safe. There are many differences between what would be the best floor for various sports and forms of dance. [ [http://www.danceuk.org/metadot/index.pl?id=24220&isa=Category&op=show Harlequin article on basic considerations for dance floors] ] However the requirements are similar enough that one can have a floor suitable for general use; and any exceptions like judo would expect to put down their own mats anyway. [ [http://www.judoinfo.com/tatami.htm The Quest for the Perfect Judo Floor] ]

This article deals mainly with requirements which are common across different disciplines. The performance surface article deals more with customization for different activities.

These basic requirements are covered in more detail in the standards listed below.

* Like a good race track it should have just the right amount of give; it should not be too hard which causes repetitive strain injuries or too soft which is tiring.
* It should be even and flat with only small variation in characteristics across it.
* It should be springy and return energy to lift the feet when moving, but not too springy like a trampoline.
* It should absorb the energy of falls and reduce injuries.
* It should have appropriate traction: too much and the foot might twist when turning, too little and it can be dangerously slippery.
* There should not be any sideways movement. Sideways movement hampers balance, this is why very thick pile carpeting can be dangerous for the elderly (thick underlay however is good).
* It should be primarily ‘area elastic’ rather than ‘point elastic’. It should depress more like a wooden floor than a sponge rubber one – but the effect should not extend too far and the surface layer can be point elastic.
* It should be easy to see action on the floor: it should not be too light or dark.
* It should not be either too noisy or too quiet in use.
* It should not become very dangerous if liquid is spilled on it and it should be easy to clear up any such spillage. This is a major cause of injury.

Additionally many such floors are multipurpose. For instance a community hall might be used for playgroups and old age groups, for dances, aerobics and sports, and for seating for plays. It may have to carry heavy objects like pianos. There may also be requirements for ease of cleaning and maintenance. Cost of repair after damage by vandals or stiletto heels is also a consideration. Note the requirement to host public events can often be eased by the use of a gym floor cover to protect the floor.

There is no combined standard covering playgrounds and sprung floors or for use in old age centres but one that conforms to a full minimum sports or dance standard should be adequate to prevent serious injuries (e.g. broken bones) for children falling from 2 feet (0.6 meter) as from a toddlers table, or hip injuries in the elderly. [ [http://www.en1177.com/ Safety surfacing] ] [ [http://www.rospa.com/homesafety/info/flooring.pdf Can flooring and underlay materials reduce the number of hip fractures in the elderly?] ]

Construction of a sprung floor

There is a FAQ on 'Build your own dance floor' on the web. [ [http://www.eijkhout.net/rad/dance_offnet/floor.html Build your own dance floor] part of the FAQ list for the newsgroup rec.arts.dance]

Sprung floors come in a few major types: [ [http://www.calarts.edu/~dk/flooring.html Dance Floors] including a FAQ]

* Traditional wood basketweave
* Wood with high durometer neoprene pads. Sometimes both basketweave and neoprene pads are used.
* Foam rubber with a wood or other area elastic layer on top
* A few sprung floors use actual springs! The special floors used by cheerleaders and tumblers often have coil springs under them.

The construction may be built into the area, or composed of modules that slot together and can be disassembled for tours.

Halls should be designed and built with sprung floors in mind leaving at least 10cm for the floor. The depth is a major constraint when laying a sprung floor in a hall not designed for it. About 5cm is about the maximum one can normally accommodate, and some sprung floors designed for refurbishments are as low as 3cm. [ [http://www.boen.com/ Boen Sports Floors] Their Boflex range of floors are only 28mm high] Ramps for wheelchairs will be needed at the doors, and if as is usually desirable the ramp is outside the hall the doors will need the bottoms trimmed off (easing), and so their height will be reduced. Ramps can have a 1 in 12 incline at most and they may also need a safety zone round them. Thus if the floor is 5cm deep the ramp needs to be 60cm long or more.

The underfloor needs to be made flat either with levelling cement, very careful trowelling, or by using shims or a layer of masonite. Any new cement must be left at least a month to dry. A membrane vapour barrier must be used to prevent damp from the ground.

A semi-traditional floor would have wood battens laid on neoprene pads. Neoprene lasts much better than rubber, they are typically laid 40cm-50cm apart and are 1cm-2.5cm thick. Then more wood battens are put on top at right angles half way between the pads. A traditional floor might have three layers of this springing. Then two layers of plywood at 45 degrees or maybe 90 degrees are placed on top making sure the joins don't match up. The plywood spreads the load. And lastly a layer of good durable wood like oak, beech or maple provides the surface - or less good wood covered with a vinyl surface. There may also be provision to stop the floor depressing too much if a very heavy weight is placed on it.

There should normally be a fairly wide gap between the floor and the wall to allow for expansion and to allow air to circulate. This will be covered by a skirting board or moulding and so is not normally evident. It is because the floor is free standing rather than being connected to walls or joists that it is also referred to as a floating floor.

The performance surface is normally of vinyl or hardwood, engineered wood or laminate. For dance the surface may be replaceable so for instance a theatre can adapt easily to either ballet or tap dance.

Generating power from dance

A number of green nightclubs have installed sprung floors which generate some of the power for the music and lights. The floors are sprung using actual springs, the floors are also suspended on tranducers that act like shock absorbers but using piezoelectric crystals to absorb the energy. These crystals generate electricity when compressed and then released, this charges nearby batteries. The batteries smooth the power so the lights don't go off between beats! [ [http://www.huffingtonpost.com/2008/06/20/green-nightclubs-harness_n_108266.html Green Nightclubs Harness Sustainable Power Of Dance] Huffington Post June 20, 2008] [ [http://www.treehugger.com/files/2006/10/the_sustainable_4.php The Sustainable Dance Club] Video]

Open and closed cells

The neoprene pads used in sprung floors may be described as having open cells or closed cells. A cell is a void inside the neoprene, there may be just one big one or many small ones.

A closed cell is like a balloon - the air inside cannot escape and the pad is bouncy and returns most of the energy put in. A pad with many small closed cells may also be referred to as a foam, but typically only a single large closed cell is used as the cell can expand sideways and so provides characteristics more like a long spring.

Open cells have small holes which let the air inside escape and tend to dissipate the energy input. A pad with many open cells may also be referred to as a sponge.

As with everything to do with sprung floors a compromise of both is often used. A core of softer durometer may have a harder outer layer shaped so that heavy falls encounter more resistance instead of 'bottoming out' to a concrete subfloor. This also protects against deformation by heavy weights like pianos.

Standards

The same standards are applicable to dance as to sport. These describe minimum standards suitable for a general purpose hall. The ranges of parameters are wide enough to cover optimizing most special purpose halls as well:

* DIN 18032 part 2 is the German standard and is generally considered current best practice. [ [http://de.wikipedia.org/wiki/DIN_18032 DIN 18032] German wiki]
* BS 7044 part 4 is the British standard for artificial sports surfaces. [ [http://www.bsistandards.co.uk BSiStandards] ] The Sports Council only supports indoor activities on a BS 7044 approved floor and have a good description of them. [ [http://www.sportengland.org/floors.pdf British Sports Council: Floors for Indoor Sports. Design Guidance Note] ]
* EN 14904 is a new European standard which will replace European national standards. [ [http://webstore.ansi.org/ansidocstore/product.asp?sku=DIN+EN+14904%3A2006 From Ansi, EN14904 Surfaces for sports areas - Indoor surfaces for multi-sports use - Specification (FOREIGN STANDARD)] ] This was used for the World Cup in Germany, and covers both sports and dance halls. It also deals explicitly with some special purpose floors.

History

There doesn't seem to be a researched history of sprung floors. There would not have been much perceived need till recently when concrete slabs started being generally used for sub-floors. Before then floors were mainly either earthen or used wood on joists, both of which provide some cushioning from shocks. Early sprung floors often used leaf or coil springs whence the name, these floors tended to bounce, modern floors have suppressed this 'trampoline' effect and so are often called "semi-sprung".

The earliest references on the web seem to be:

*The New Zealand Prime Ministerial home was rebuilt soon after 1872. The rebuild included a ballroom with a sprung floor and New Zealand's first lift. [ [http://www.primeminister.govt.nz/premierhouse.html Premer House - Echoes of the past] New Zealand 1872]
*A purpose built dance hall with a still functioning sprung floor was built in Over-the-Rhine in 1885. [ [http://www.uc.edu/news/NR.asp?id=1382 Students Step in to Help Preserve Historic Dance Hall] Germany 1885]

Many sprung floors were installed for dance soon after 1900 in places like embassies, hotels, and private clubs. Use of sprung floors exploded with the opening of large public dance halls between 1920 an 1945.

The use of sprung floors for sport date to the 1936 Olympics in Berlin, before then floor exercises were performed on grass [ [http://www.gymmedia.com/ag/history/appa/floor/history_fx.htm History of FLOOR EXERCISES] ] [ [http://www.acrobaticsports.com/detail.do?noArticle=1705&id_key=0 Through The Years: How the Competitive Tumbling Floor Evolved] by Jim Bertz] Platforms with springs for professional acrobats probably date long before this.

ee also

* Dance floor
* Floor (gymnastics)
* Performance surface

References

* http://www.dancing-times.co.uk/DT200405/dancingtimes200405-1.html