Help - digging under the house and how much

I have a 1960's double brick house with brick piers under the house. And the house is on a gently slopping piece of land. At the back the house is almost 1 storey higher than ground level. So I thought it's a good idea to dig out a bit of dirt under the house and I can make a store room out of it.
As I was digging I notice there is a thin layer of white powder (lime???) a few inches under the loose dirt. I did a bit of google and couldn't find any thing useful. What is this white powder layer for? Is there any harm in digging it out?
Can anyone give me some idea on this one please? :confused:

Many thanks.
You found white powder under the house and you want us to tell you what it is? :confused:

Possibilities are endless from "it was a drug house and it is cocaine" to "lime" to "who knows what". Take a sample down to your chemist and he might run some tests for you CSI style. ;)
If it were cocaine that would make me rich. :rolleyes: On a second thought might land me in jail too.:p

But if it was calcium hydroxide what is the purpose of that layer?
Keep pests away? keep ground dry? I am not sure.
Is it an excess sheet of plaster buried there, or is it actually in the foundations? in which case you probably shouldn't dig under them.:)
Hi Battler,

It's definitely not an excess sheet of plaster because it wouldn't be so uniform and in all areas under the house.

If it's in the foundations, what's the purpose of this layer and what bad things might happen if I do?
My only other guess, if it is actually in the constructed foundations, it may be part of a damp course......but I doubt it would be white and powdery.
lime was sometimes used in the past around foundations to deter white ants...not sure if this is what you are faced with though.

similar in fashion to the old chestnut about sprinkling talc across a trail of ants to get rid of them.
lime is used for marking footings , before the excavator starts the cut, be care full not to go past the exclusion zone, which is an imaginary 45 deg line from the bottom edge of the footings, the footings should be about 500mm deep.