N
Newboy
Your OP stated 20 m²
"If
the floor area of the building is between 15 square metres and 30 square metres, you will not normally be required to apply for building regulations approval
providing that the building contains NO sleeping accommodation"
and
is either at least one metre from any boundary
or
it is constructed of substantially non-combustible materials."
It's worth checking that you don't fall foul of the planning rule
"No verandas, balconies or raised platforms."
"If
the floor area of the building is between 15 square metres and 30 square metres, you will not normally be required to apply for building regulations approval
providing that the building contains NO sleeping accommodation"
and
is either at least one metre from any boundary
or
it is constructed of substantially non-combustible materials."
It's worth checking that you don't fall foul of the planning rule
"No verandas, balconies or raised platforms."