garden office roof height

[bolst3r]

I know this is a stupid question(s) to ask – sorry.

I've looked at loads of sites but I just need a sanity check as I seem to be going round in circles...

I have to build a garden office, it's within 2m of my boundary and will have a single flat roof.

All the things I've read say the maximum overall height is 2.5m. Is this from ground level or the height of the building as I was planning on raising it off the ground on piles to encourage air flow and deter water ingress. I was also planning on giving it a warm deck roof as it's more thermally efficient however by the time the floor and roof are insulated i'll be left with a really low ceiling height of 2m

I'm not missing something here am I? I've seen loads of prefab garden offices and they all come in at the 2.5m level... Guess they might be skimping slightly on the thermal efficiency and also going for cold deck roof to overcome the ceiling height problem.

Any guidance would be appreciated.

 

[HERTS P&D]

From what I remember when I built one in my old house was:

3m from ground to top of roof height - flat roof.

4m from ground to top of roof height- pitched roof.

Also it has to be a minimum 1m from all boundary fences if made from timber.

Andy