Liquid roofing is the process of

waterproofing Waterproofing is the process of making an object or structure waterproof or water-resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environme ...

roof A roof ( : roofs or rooves) is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of t ...

by the application of a specialist hydrophobic

liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, ...

roof coating A roof coating is a monolithic, fully adhered, fluid applied roofing membrane. Many roof coatings are elastomeric, that is, they have elastic properties that allow them to stretch and return to their original shape without damage. Typical roof coa ...

. It can be applied to most roof styles, including flat, pitched, and domed ones.

History

The concept of liquid roofing has existed since the early 1800s, when natural

bitumen Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...

was combined with

jute Jute is a long, soft, shiny bast fiber that can be spun into coarse, strong threads. It is produced from flowering plants in the genus ''Corchorus'', which is in the mallow family Malvaceae. The primary source of the fiber is '' Corchorus ol ...

straw Straw is an agricultural byproduct consisting of the dry stalks of cereal plants after the grain and chaff have been removed. It makes up about half of the yield of cereal crops such as barley, oats, rice, rye and wheat. It has a number ...

, rag felt and other man-made materials to provide a waterproofing solution for roofs. In the early 20th century, the manufacture of liquid roof coatings became a commercial activity, with the earliest coatings being based on liquefied rubber. The 1960s and 1970s saw the introduction of acrylics, acrylic

emulsions An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althoug ...

, Styrene-butadiene and unsaturated

polyester Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natura ...

s, which led to improved quality and durability of the coatings. In 1975, the first water based

elastomeric An elastomer is a polymer with viscoelasticity (i.e. both viscosity and elasticity) and with weak intermolecular forces, generally low Young's modulus and high failure strain compared with other materials. The term, a portmanteau of ''elast ...

roof coatings were introduced; in the late 1980s, single component moisture-cured

polyurethane Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced from ...

coatings were developed; they remain the basis of the majority of today's cold liquid applied roof coating technologies.

Concept

Liquid roofing involves the application of a monolithic, fully bonded, liquid based coating to a roof. The coating cures to form a rubber-like

waterproof

membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. ...

, capable of stretching and returning to its original shape without damage. Such coating systems are usually reinforced with secondary materials such as

glass-reinforced plastic Fiberglass (American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass clo ...

to provide additional

tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials ...

. The coatings can be applied over most traditional roofing materials, including

felt Felt is a textile material that is produced by matting, condensing and pressing fibers together. Felt can be made of natural fibers such as wool or animal fur, or from synthetic fibers such as petroleum-based acrylic or acrylonitrile or wood ...

asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...

, bitumen, and

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

. Liquid spray-applied roofing membranes have been one of the fastest growing roofing systems in North America and Europe.

Benefits

Cost-effectiveness

The process of liquid roofing provides a cost-effective method of making a new or existing roof waterproof because it's estimated 70% less expensive than overall roof replacement for refurbishment.

High performance

Liquid roofing can be undertaken with high performance materials. Many of the products used in the liquid roofing process have been independently tested and their performance verified.

Safety

Unlike the installation of felt, asphalt and bitumen membranes, liquid roofing does not involve hot works. Hot work on roofs is an extremely high-risk process that poses a significant fire risk to contractors as well as to the building and its occupants. The coating material used in the liquid roofing process is applied cold, thus negating any fire risk.

Encapsulation

When applied, liquid roofing systems encapsulate the surface they are applied to, preserving whatever is underneath and protecting it from weathering. This is especially desirable when dealing with

asbestos Asbestos () is a naturally occurring fibrous silicate mineral. There are six types, all of which are composed of long and thin fibrous crystals, each fibre being composed of many microscopic "fibrils" that can be released into the atmosphere b ...

roofs, as attempted removal of asbestos roofing can damage it, releasing material that can trigger

asbestosis Asbestosis is long-term inflammation and scarring of the lungs due to asbestos fibers. Symptoms may include shortness of breath, cough, wheezing, and chest tightness. Complications may include lung cancer, mesothelioma, and pulmonary heart ...

. Using a liquid coating system instead seals the asbestos, thus making disturbance of the material more difficult.

Easy application

Application is simplified by fast curing as well as a high resistance to extreme temperatures (between -40 °C and +80 °C). Minimal equipment is needed in installation.

References

{{Reflist Roofs