I haven't a clue really but I did a couple of googles and came up with this;

http://www.youtube.com/watch?v=plNtu6j1WHE&feature=related

It doesn't tell you much but the size looks the same size as yours.

Then I found a supplier who sells his trees in five litre pots but did not give a size of the tree but I would guess they would be under 2ft high.

Based on this I would guess a 6ft specimen may have a root system of around four times that much so if it were in a pot it would be around 20-25 litres or if you like the size of a five gallon drum.

So my guess is; a root spread of two to three foot to a depth of around 12" to 18" deep.

But as I have said......its only a guess!

I'd agree with TG's guess and wonder how you actually plan to move...

Thanks for the video and research- i'm sure it will come in handy!:)

I recently moved a 5' monkey puzzle tree. Root ball was not massive, maybe 2' across, 1.5 ft deep, but it also had a single long, fat root, which I followed for as far as possible then chopped it off (at around 5 ft long). It has survived the replanting now for a year and is quite happy.

P.S. Get the elastoplasts ready, it's nearly impossible to avoid injury :-)

Thank you Sophie, thats really helpful, and i will get the plasters at the ready. kind regards. Carol