The project scope included the demolition of an old annex building to the School , the construction of a new 24 – classroom extension block , and conversion works at the existing premises of the School to provide additional facilities . The main building of St . Paul ‘ s Primary Catholic School is a Grade 2 historic building . Therefore the project was subject to a Heritage Impact Assessment ( HIA ) in which the construction works and further maintenance have to comply with relevant requirements . Caltite waterproofing has been used in the no – membrane design for the pile cap and slab , for the permanent DRY ! protection for the special building .