What’s a waterproof membrane?

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A waterproofing membrane is a layer that prevents water passage, commonly used in construction and clothing. It is often sandwiched between two layers and can be multiple layers thick. Waterproofing is a matter of degree, and water-resistant materials allow some water penetration. In clothing, the membrane is chemically bonded between two layers of fabric. In construction, membranes are found around foundations and basement walls, and can be made of synthetic or natural materials. Internal membranes are similar to those in clothing, while external ones are stronger and placed directly against the building exterior.

A waterproofing membrane is a layer of material that prevents the passage of water. These materials are used in a wide variety of products, but the term is generally used when referring to construction or clothing. In both cases, the membrane is usually placed between two other layers. This both protects the waterproofing membrane and creates a physical part that separates waterproof and non-waterproof areas. When used in construction, it is not uncommon for there to be multiple layers of waterproofing membrane both within the building and in the surrounding areas.

Waterproofing is often a matter of degree rather than certainty. Two items that are both waterproof can allow small amounts of water to enter them under completely different circumstances. These substances are in contrast to water resistant ones, where water can pass through them to some extent under any circumstances. For example, a waterproof membrane can hold water completely in most situations, but if it’s too hot or too cold, small amounts will pass through. A water resistant layer would allow penetration regardless of temperature.

When a waterproofing membrane is used in clothing, it is usually very light and brittle, similar in thickness and weight to a plastic garbage bag. These layers are sandwiched between two layers of fabric and chemically bonded. It is important that the fabric is not sewn, as this will create non-waterproof holes in the layer. This multi-layered material is then placed within the clothing, usually in conjunction with additional layers of protective padding. These layers are common in jackets and footwear, as they often consist of multiple layers anyway.

In construction, most waterproofing membranes are found around the foundation and basement walls. These layers are usually within concrete walls, along the exterior surface of submerged areas, or strategically placed around the building. Because people don’t need to wear them, they are thicker and more durable than those found in clothing, but are still prone to accidental punctures. In addition to synthetic membranes, some buildings use layers of natural material to discourage water movement or channel it into specific areas.

When placed inside a wall, the actual construction of a waterproofing membrane is nearly identical to inside clothing. The membrane is bonded to other materials, often directly to the wall or a hard secondary material, and placed within a wall cavity. These layers allow water to penetrate half of the wall, but prevent it from penetrating the other half.

External waterproofing membranes are not usually sandwiched like internal membranes and are, therefore, designed to be much stronger. Most are positioned directly against the building exterior, preventing water entry altogether. These are common in most new construction and are considered part of a standard building envelope.




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