Evalon Explained

The base material for the Evalon Polymer Membrane System is a heavily modified PVC (Polyvinyl Chloride) compound. PVC in its many different forms is widely utilised throughout construction and manufacturing, where it is recognised for its durability, flexibility and resistance to ultra-violet radiation (UV). PVC has now in fact replaced many more construction materials than most of us realise. In our homes traditional (and expensive) copper water piping has become obsolete, with flexible PVC piping supplied in coils up to 30 metres long resulting in fewer joints and greater heat retention. The properties of PVC are such that these pipes are designed to carry water from a boiler at up to 82 degrees under high pressure, without adverse effects over the lifetime of a building. In its more rigid form PVC is also responsible for carrying waste from our sinks, toilets, baths and showers whilst being maintenance free and never requiring painting. This doesn't stop at the soil pipe dissapearing into the ground at the side of your house, thanks to its toughness and long term durability PVC has also replaced heavy and expensive cast iron as the material of choice for sewage, storm water, and underground drainage piping.

In fact the vast majority of us already rely on PVC to keep the rain, wind and intruders out of our homes. Over the last 30 years U-PVC (unplasticised-PVC) doors, windows, fascia boards and guttering etc have made our homes infinitely more secure, warm, comfortable and attractive, whilst eliminating the need for maintenance.

The use PVC polymers for flat roofing was pioneered in Germany and Switzerland in the 1960s, and arrived in the the UK in the 1970s. Specialising in flat roof membranes since 1964, Alwitra GmbH is one of the longest established companies in this field. Recognising the unbeatable attributes of PVC, Alwitra in co-operation with Du-Pont developed a rugged, highly flexible plasticized PVC Polymer which fights weathering and chemical attack, withstands extremes of temperature, and remains flexible down to -30 degrees. Evalon is now regarded as the ultimate in flat roof waterproofing, and is produced in rolls up to 2 metres wide, all site seams consist of a minimum 50 mm overlap, the two sides of which are homogenously welded and permanently become one, creating a double layer which is stronger than the membrane itself, and does not involve any other substances such as glues etc. A good indication of the strength of an Evalon weld is the fact that U-PVC doors and window frames etc are simply made from lengths of U-PVC cut to length and welded together at the corners by the same principle as Evalon PVC is welded together on a flat roof.

Over 90% of flat roof leaks and failures are a result of defective edge details, many systems do not include edge trims and require "improvised" details to be produced on site, where edge trims are included most systems use plastic. The forces of expansion and contraction between differing materials also play a large part in such problems. For these reasons Alwitra has designed a range of edge trims and wall flashings fabricated solely from light gauge galvanized steel, which are laminated in Evalon to allow a homogenous seam weld between the membrane and edge trims, creating an airtight seal. These are mechanically fixed in to the roof deck (and brickwork where flashings are involved) using approved fasteners, and can realistically be expected to outlive the structure they are attached to.

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