Recently I did a Facebook post in which I assumed a fairly high ground and stated that;
“ At STM Studio supplies we constantly come across people planning to use particle board for their dance floor. I cannot emphasise strongly enough what a bad idea that is. There is no international supplier of performance flooring that will recommend particle board as a sub-floor. By manufacture and intent, chip or particle reconstituted material is very dense and in comparison to plywood “dead” with a much-reduced energy return. Since this energy return and shock absorption is the reason why we are building a sprung floor in the first place, it defies reason to use a material that is going to lessen that.
Plywood, strand-board, sprung battens, or a combination of them are the only way forward. The labour component is the significant cost and this remains largely unchanged. The effective return on the investment in plywood is more than rewarded with the improved quality of the finished floor”
Please listen to those who know rather than builders who profess to.
This created a bit of a fuss, as many studio owners and dancers, pre-committed to particle board flooring, were naturally defensive and requested I support my claims a little more scientifically.
This created more of a challenge than I anticipated. It seems there is little incentive out there to compare the deflection or bending characteristics of the two different materials in a direct comparison. As a bit of background to all this are the relevant standards, or lack of them, relating to dance or “performance floors”.
Australia and New Zealand have no specific guidelines for performance floors but AS 1702.2 relates to timber properties as being discussed here, as does NZS 3604:2011.Both require a KPa of under 3.
kPa refers to the pascal (Pa) or kilopascal (kPa) as a unit of pressure measurement and is widely used throughout the world In this instance as a measure of ground pressure.
So far neither plywood or particle board is offending if it is supported at a minimum of 450 centres as per table 5 In the excellent EWPAA “Commercial and Industrial Flooring Design” article.
The closest we get to a performance floor standard is the Din Standard 1083 part 2 which is the mother of the now widely applied European standard EN1904. As these standards are for sports floors we are only concerned with the elements that directly relate to dance.
One is the area elasticity of the floor which is to do with the area around the point of impact which will, for example affect your partner. Another is shock absorption with a force reduction of between 25% and 75% and in common acceptance regarded as “good” around 53%. Add to this “point load” which is defined as the deflection of a point force only at or close to the point of application of the force. Most relevant to this discussion is “vertical deformation” which indicates the ability of the surface to deform under load.
Obviously as a desirable dance floor is a combination of several factors including thickness, hardness and uniformity of supports but specific to the plywood vs. particle board debate is this issue of vertical deformation.
When tested by the EN 14809 methods, in a general sense, both plywood and MDF fall well below the vertical deformation limit of 5mm. I say in a general sense because there a big range of variables within those two materials. Obviously thickness and composition are part of that difference, however for this application, as dance flooring, we can pretty much limit ourselves to 15-17mm interior plywood and 19mm Yellow tongue flooring whilst not excluding
the excellent birch ply products supplied by both Harlequin and Stagestep.
Information on particle board behaviour wasn’t as difficult as plywood, with an article on shelving properties containing most of the required information. Particleboard, also known
as chipboard and as yellow tongue when used in flooring, is an engineered wood product manufactured from wood chips, sawmill shavings, or even sawdust and a synthetic resin or other suitable binder which is pressed and extruded. Particle board is cheaper more dense and more uniform than conventional wood and plywood and is substituted for them when cost is more important than strength and appearance. A major disadvantage of particleboard is that it is very prone to expansion and discolouration due to moisture. The denseness in this application is also not necessarily a plus as has a lessened ability to return the energy imparted to it.
Particle board is governed by Australian Standards (AS/NZS 1859 Parts 1 and 2 and 1860 Part 1). with testing carried out by Timber & Wood Products Research Centre of the University of Central Queensland, results below were rechecked and updated by additional research projects carried out by the Caulfield Campus, Monash University.
Particle board flooring has a nominal deflection of 1.8mm under a uniform load of 21 KPa.
With the human footprint of a 1.8m male being around 55Kpa this will increase but not necessarily proportionally.
This study also mentions that in tropical areas, with material exposed to the interior effects of weather cycles of temperature and relative humidity, the creep factor is three times initial deflection. If particleboard is exposed to severe tropical weather conditions a creep factor of four should be used. Flooring grade improves on these figures but is still subject to creeping.
Whilst this increased deflection may seem desirable, remember that, what this is describing includes swelling, softening and a non-returning deflection or slump.
Conversely and significantly, interior grade ply flooring plywood manufactured to AS/NZS 2270 because it’s natural wood structure is maintained during manufacture, all moisture movements for practical purposes can be considered reversible.
Plywood is a sheet material manufactured from thin layers or “plies” of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another All ply woods bind resin and wood fibre sheets to form a composite material. This alternation of the grain is called cross-graining and has several important benefits: it reduces the tendency of wood to split when nailed at the edges; it reduces expansion and shrinkage, providing improved dimensional stability; and it makes the strength of the panel consistent across all directions. There is usually an odd number of plies, so that the sheet is balanced—this reduces warping.
Further, plywood’s cross laminated construction makes panels highly resistant to edge and impact damage.
The ability to relocate a plywood floor is also enhanced for this reason, plus the smaller sheet size, weight, and reduced moisture retention.
Additionally, fatigue from cyclic loads is not a problem.
Annoyingly, what deflection information is available was substantially limited to structural plywood, but we could glean that with a uniform load of 3kPa on 17mm radiata plywood had a nominal deflection of 2mm. Once again there is untested proportional decrease in efficiency but suggests there is potentially a 7x gain on the performance of particle board.
Since we didn’t believe this we ran some tests of our own.
Essentially we supported our materials on the perimeter of a 1200 section maintaining a 1m span.
On this stood a 74kg man and we measured the change in level.
– 18mm radiata ply: 18mm
– 19mm yellow tongue: 4mm
– 15mm ply with 5.5mm masonite: 14mm
Significantly, the plywood sprang back into position immediately. Remember that, unlike in this test, the floor is supported at 300mm centres so that dipping is not going to occur.
I reached out to Dr Luke Hopper the ballet dancer turned Biomechanist about this issue. He rightly pointed out that more conventional sports floors do not use particle board and tend to use hardwood strip timber. Those of you that have a church hall or similar know well how satisfactory that can be.
Cost is always going to be an issue. In Australia using Bunnings as a national supplier and as at March 2017, Yellow tongue flooring will cost $13.88/m2 and an equivalent ply $26.04/m2. Although this is roughly double the price on an average 80Mm2 floor this is an added cost of $972.80. Even if the floor should only last 10 years, and expect 20+, then this is $1.87 a week. The other costs such as sprung pads, vinyl and most importantly labour
remain constant across the exercise.
The choice is of course yours but here is what a builder in the UK who does know had to say: “Although you may be enticed by the cheaper chipboard flooring, I have to strongly advise you not to be. Chipboard really doesn’t cut the mustard.” He goes on at length and has a good Q &A as well
Finally may I leave you with this thought from Benjamin Franklin;
“The bitterness of poor quality remains long after the sweetness of low price is forgotten”