The Stiletto Test

picture of feet in stiletto shoes
picture of feet in stiletto shoes

The Stiletto Test

It is important we know how hard the various timbers are, but with over 1,000 potential species here, many of which are extremely rare, the oft referred to ‘Janka’ hardness test figures cannot provide the data. The Janka test measures the force required to half embed a small steel ball (11.28mm diameter) into a sample of the timber. Depending on which country the data is taken from, it can be measured in different units so the figures may not be comparable, and anyway the same species grown in different places has different hardness ratings. So given there are many different species of each genus (there are more than 50 Oaks with another 17 cultivars; over 48 Maples with a further 45 cultivars), the data could very easily be misrepresented.

So what to do?

Well, as with so many issues, it was time to develop our own test so all species we offer can be tested on exactly the same basis. In this way all are comparable and meaningful.

picture of stiletto heel on timber test panel

The Stiletto test directly compares the damage from an identical force by measuring the depth of the indentation caused – logical as one of the biggest issues will be ladies on stilettos – beautiful as they may look. Simple really, and it can be done on every tree if there is a need.

Rocking Test ImageBut just to be certain how several species will perform – yes you guessed it – we asked a lady in stilettos to walk our planks in 3 ways:

  1. Without haste along them.
  2. Hurriedly along them.
  3. To impose the maximum damage by doing the rocking test – where she put all her weight through just the rear edges of the heels!
    Along with this we tested both steel heels and plastic ones.

To get stilettos into perspective, let’s consider the load she imposes through the heel: [figures for a 50kg or 8 stone lady].

  Tons/sq m Tons/sq ft
• Stood on one foot with the shoe flat down (half stride): 227 25.7
• Landing on the heel with it flat when walking: 554 51.4
• Landing on the heel with the shoe not flat: 2000+ 186+
Elephant Image

So now we can see why the force a high heel can put down is greater than a bull elephant manages! It is enormous, and compares with about 3.5tons/sq m for a flat shoe with instep.

The physical stiletto test was done after the technical test results were known and on 12 selected species from the hardest to one of the softest general softwoods. We found as follows:

Rocking Test Image

  • The rocking test marked everything including timbers harder than oak, but it was with the steel heels.
  • When Jules (the lady) walked as she does [almost perfectly] along the samples – not one marked. But she lands fairly flat without the heel hitting at an angle first.
  • Two samples marked ONLY when the rocking test was done and not even for the hurried walk – sycamore (a maple) and beech. The Oaks did mark.
  • The sample all the photos were taken on was Silver Fir – a softwood – and there are no marks to be found on it in spite of many tests, weight shifts and standing on one leg for some time.
  • The plastic heels were much less damaging than the steel ones, but they were slightly worn and the steel tips were not actually flat as they had small grooves in them. All the harder timbers survived

It is clear, as expected, that wooden floors are not designed for stiletto loads, but if care is taken all but the softer ones are fine. The real problem is when there is grit either on the floor or under the shoes, and there is no timber that can survive such an attack without showing it was abused. Through most of the world nobody expects or allows people to walk around their homes in their outdoor shoes, and across all the old soviet area reaching more than about 2m from the front door with shoes on would seriously offend. It is honestly faintly surprising that we assume we do go from street to floor, and for as long as I can remember I have always taken shoes off inside the door – and everybody does this in Tranquility. Working on this principle there are no timbers you cannot use, and given that the hardest timbers tend to grow in tropical rainforests; grow straight for the light; grow under constant conditions through the year and therefore have no interesting feature or colour – why shouldn’t we enjoy all the beautiful timbers grown in these latitudes and in the UK in particular. See ‘What not to use’ and ‘Softwood v Hardwood’.

The test figures have been translated into hardness figures where no indentation (i.e. extremely hard) scores 100. The scale was taken so that the softest scored 40 and for the technically minded a linear graph was used. The figures are shown against each timber but they can be found below in hardness order which may surprise a few.

So choose your floor timber; look after it and enjoy it.