Membrane Roofing Materials
For thousands of years man has had to find ways to deflect water off flat roofs to prevent leaks. The most common materials used until about 25-30 years ago were asphalt compounds known as tar and pitch. Asphalts being used are not as common as it once was but it is still used in certain circumstances today.
With advances in roofing technology due to an explosion in the synthetic rubber and plastics industries, advanced membrane products have become more common in the marketplace. First appearing about 40 years ago, these products essentially “shrink-wrap” your roof and keep water from entering. Without this technology we would still be worrying about leaks just as often as our ancestors did.
Three Basic Types of Membrane
The three basic types of roofing membranes are Thermosets, Thermoplastics, and Modified Bitumen Membranes. Thermoset membranes are the most effective and popular.
These membranes are designed with special compounds that actually connect to each other once installed. These membranes chemically link, creating a seam that causes the membrane to act as a single piece of synthetic rubber covering your house. Since these compounds chemically link together, you have a much better seal than with any of the other products. Synthetic rubber roofs (EPDM), CSPE, CR, and ECR membranes all fall into this category. These membranes are between 30-60 mils which is relatively thick for roofing membrane. These membranes offer performance and peace of mind under a variety of circumstances. If installed to the manufacturers’ specifications, they will keep your home leak-free for many years.
Thermoplastic membranes are very similar in nature to Thermoset Membranes, except for the fact that there is no chemical connection. Instead, seams have to be welded together with heat or chemical solvents. If the welds are made properly they will be just as cohesive as the Thermoset membrane but if not, you may be catching water in buckets.
The types of material that compose this group are PVC plastics, CPA, CPE, EIP, NBP, TPO, and PIB. Your roofer knows what all these acronyms stand for so make sure to ask before they install anything so you know what you’re getting.
Modified Bitumen Membranes
These membranes harken back to the old method of water-proofing by combining asphalt with modifiers and other reinforcement materials. These membranes can perform very well if done correctly but they are not as advanced as the other two options. This system works by creating a “sandwiched” roofing material. You may hear your roofer refer to this type of membrane as APP, SBS, or the more popular “torch-down” roof, because a large blow torch is required to melt asphalt to join the seams together properly.