Waterproof or water-resistant describes objects relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environments or under water to specified depths. Waterproofing describes making an object waterproof or water-resistant (such as a camera or watch).
"Water resistant" and "waterproof" often refer to penetration of liquid water. Permeation of water vapor is reported as a water vapor transmission rate. Also, water from condensation is usually separate from "water resistant".
The hulls of boats and ships were once waterproofed by applying tar or pitch. Modern items may be waterproofed by applying water-repellent coatings or by sealing seams with gaskets or O-rings.
In construction, a building or structure is waterproofed with the use of membranes and coatings to protect contents underneath or within as well as protecting structural integrity. The waterproofing of the building envelope in construction specifications is listed under '07 - Thermal and Moisture Protection' within MasterFormat 2004, by the Construction Specifications Institute, and includes roofing material as well as waterproofing materials.
Waterproofing is used in reference to building structures (basements, decks, wet areas, etc.), watercraft, canvas, clothing (raincoat, waders) and paper (e.g., milk and juice cartons).
Waterproofing should not be confused with roofing, as roofing cannot necessarily withstand hydrostatic head, and waterproofing can.
The standards for waterproofing bathrooms in domestic construction have improved over the years, due in large part to the general tightening of building codes.
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In building construction, a structure needs waterproofing since concrete itself will not be watertight on its own (but note concrete is easily waterproofed with additives). The conventional system of waterproofing involves 'membranes'. This relies on the application of one or more layers of membrane (available in various materials: e.g., bitumen, silicate, PVC, EPDM etc.) that act as a barrier between the water and the building structure, preventing the passage of water. However, the membrane system relies on exacting application, presenting difficulties. Problems with application or adherence to the substrate can lead to leakage. In the UK these membranes are rarely allowed below ground below the water table.
Over the past two decades, the construction industry has had technological advances in waterproofing materials, including integral waterproofing systems as well as more advanced membrane materials.
Integral systems work within the matrix of a concrete structure, giving the concrete itself a waterproof quality. There are two main types of integral waterproofing systems: the hydrophilic and the hydrophobic systems. A hydrophilic system typically uses a crystallization technology that replaces the water in the concrete with insoluble crystals. Various brands available in the market claim similar properties, but not all can react with a wide range of cement hydration by-products, and thus require caution. Hydrophobic systems use fatty acids to block pores within the concrete, preventing water passage.
New membrane materials seek to overcome shortcomings in older methods like PVC and HDPE. Generally, new technology in waterproof membranes relies on polymer based materials that are extremely adhesive to create a seamless barrier around the outside of a structure.
Basement waterproofing once completed becomes very difficult since the water pressure is from the negative side (from outside coming inside), the difficulty arises when a membrane cannot withstand hydrostatic pressure from within the substrate and therefore fails. Water may enter a basement through various means including through joints, walls, or floors. Various basement waterproofing systems address these problems. There are many systems available of varying cost, effectiveness, and installation invasiveness. Specially used membranes in this field are protection board sheets. Basement waterproofing may be done internally and externally. Because basement foundations can be brick, block, concrete, and even wood, it is important to pick the right waterproofing system for the right foundation. One effective way to waterproof cracks in poured concrete walls is by epoxy injection.