Waterproofing is a means of extending the durability, beauty and usefulness of an object or structure by making it waterproof or water-resistant so that water will have little to no detrimental effect on its usefulness and purpose. Alternatively, waterproofing may be applied to enable an object to contain fluids without seepage or leaking into the surrounding area. The usual sloping roofs of buildings and construction projects are necessarily able to withstand the onslaught and run-off of water, and this is achieved through materials such as thick plastic sheeting laid underneath the roof tiles or aluminium sheeting, as well as flashing which is used around areas such as chimneys, skylights, dormer windows and heat extraction devices which are mounted in the roof. In buildings with flat roofs, specific processes are used to ensure that water has an escape route and that the roof has a waterproof covering which will be impervious to wet conditions.