Building Department Submission?!

According to s.14(1) of the Buildings Ordinance (Cap. 123), every person intending to carry out building works or street works are required to obtain the prior approval and consent from the Building Authority.
Exceptions to the above are listed out under s.41 of the Buildings Ordinance (Cap. 123), and examples include:
1. Government buildings (s.41(1));
2. Exempted building works, i.e. Building works other than drainage works, ground investigation in the scheduled areas or site formation works not involving the structure of any building (s.41(3))
(Refer to s.41 for details which are too lengthy to reproduce here)
And from s.2 of the Buildings Ordinance (Cap. 123):
Building works includes any kind of building construction, site formation works, ground investigation in the scheduled areas, foundation works, repairs, demolition, alteration, addition and every kind of building operation, and includes drainage works
Street works means any work for the construction, formation or laying out of any private street or access road, including the surfacing, channelling, draining and lighting thereof, or for the reconstruction, alteration or repair thereof
So, if the building of the things you want to build amounts to building works or street works, and does not fall within the exceptions under s.41, you need to submit your proposal to BD and obtain their prior approval and consent before commencement of works.