Keeping the old seal
Roof terraces: pathology of water tightness

In economic terms, it's clear that removing the old waterproofing is a costly operation that can often be avoided. Removal includes tearing out the running parts and upstands, thermal insulation and protection, cleaning and removal of rubble to the public dump. Of course, the supply and installation of a new vapour barrier must be added to this total.

In our experience, a good rainstorm can sometimes cause serious water damage on the top floor, just after the waterproofing and vapour barrier have been removed!