Height of an extension - does a single storey always have to start from original ground level?

ChickenLicken12

I have hunted high and low for 100% clarification of these answers and this is my last resort!!.
Does a single storey extension (no other extension in existence) have to start from ground floor level of the original property or
can it start 2m up using an existing window as the doorway that links the house with the extension?
If it starts 2m above the ground  is the overall height from ground level of the original property to which it is attached or from where the extension actually starts to be formed on a plinthe and garden?.
What is the overall height - is it the actual extension to eaves? the actual extension to pitched roof apex or the extension + roof + the additional 2m? 
I have looked everywhere for answers in every document possibly going and I just get the standard answer ...
Thank you for any help - too much lost sleep!

Doozergirl

Any extension has to start from the ground.    The ground level is the ground outside the house presently, where the extension is going to be built.  

What's the purpose of asking?  In planning, both eaves and ridgeline are important, as is the ground level.  

I don't really have an idea of what you're asking or why, I'm afraid.  

twopenny

Have you accounted for the foundations of the extension?

This could affect the damp course and stabliity of the original wall.

This is definitely a job for architects and planners to tell you.

Nearlyold

Is your existing house built on a slope or something, as above don't really understand how can you have a door that starts 2m above the floor level in the original house?

Ectophile

Nearlyold said:

Is your existing house built on a slope or something, as above don't really understand how can you have a door that starts 2m above the floor level in the original house?

Maybe it's an extension on stilts.

Nearlyold

Ectophile said:

Nearlyold said:

Is your existing house built on a slope or something, as above don't really understand how can you have a door that starts 2m above the floor level in the original house?

Maybe it's an extension on stilts.

Maybe its just going to be screwed to the outside wall of the existing building 2m off the ground or perhaps stuck on with Gripfill

silvercar

It is more common in hot countries where the houses are initially built as one storey but on stilts. Both to keep the house cooler and it means that the are under the house remains in the shade. Also, has the benefit that you can infil relatively cheaply at a later date to create a 2 storey home.
I've seen the odd house in the UK where the living areas are upstairs and the bedrooms downstairs, generally because the slope of the land means that the front and drive areas provide easier access to the upstairs. The downstairs often has most of the windows facing rearwards.