Another specialized area of waterproofing is rooftop decks and balconies. Waterproofing systems have become quite sophisticated and are a very specialized area. Failed waterproof decks, polymer or tile, are one of the leading causes of water damage to building structures, and of personal injury when they fail. Where major problems occur in the construction industry is when improper products are used for the wrong application. While the term "waterproof" is used for many products, each of them has a very specific area of application, and when manufacturer specifications and installation procedures are not followed, the consequences can be severe. Another factor is the impact of expansion and contraction on waterproofing systems for decks. Decks constantly move with changes in temperatures, putting stress on the waterproofing systems. One of the leading causes of waterproof deck system failures is the movement of underlying substrates (plywood) that cause too much stress on the membranes resulting in a failure of the system. While beyond the scope of this reference document, waterproofing of decks and balconies is a complex of many complimentary elements. These include the waterproofing membrane used, adequate slope-drainage, proper flashing details, and proper construction materials.