The roofing base sheet is a waterproofing membrane that forms the bottom layer of a multilayer roof membrane system. The base sheet is coated with modified asphalt and made from fiberglass, reinforced polyester or composite reinforcement. Asphalt enhanced with rubber or plastic polymer. The base sheets can be surfaced using heat-weldable films, sand, or release film depending upon the application.
The minimum number of sheets required to cover a low-sloped roof is two: a base and cap sheet. The base sheet is waterproof and has a surface on top that can be bonded with the cap sheet. The cap sheet is used to provide color, UV protection, and mechanical resistance. Base sheet and cap sheets must be designed in a way that they work together.
The base sheets are simple at first glance, but they vary greatly in terms of their materials, installation methods, and even the way they’re manufactured. Base sheets can be part of multi-ply systems with many layers, or a modified bitumen-based system.
Types of Roof Base Sheets
When it comes to roofing base sheets, manufacturers can choose from a variety of materials. There are many different types of roofing base sheets, each with their own characteristics and methods of installation. Here are some of the most common types of roofing sheets:
BUR: Built up roofing systems are made of many layers, so that in the event that one layer fails, there is a backup. These systems have a single base sheet but multiple components.
The base sheet of a BUR can be made from felt, fiberglass, or polyester. BUR base sheets can be impregnated either with asphalt that is unmodified or with modified bitumen. IKO will provide you with guidelines to help you choose the best base sheet for your roof based on its expected lifespan.
Modified bitumen: In essence, modified asphalt is asphalt that has rubber or plastic polymers mixed in. These polymers give the modified bitumen sheets extra flexibility, strength and durability. Modified bitumen sheets come in two main varieties.
- SBS: Styrene-butadiene-styrene (SBS) is a rubber polymer that gives the base sheet extra elasticity, flexibility and durability. IKO’s TF-95 SF-Base is one such SBS-based sheet. This fiberglass base sheet is flexible even in cold weather thanks to SBS. This also increases moisture resistance and durability.
- APP Atactic polypropylene is another rubber polymer that can be used to increase the durability and flexibility of a base sheet. The material is flexible even at low temperatures, which allows roofing contractors to install it more quickly. APP base sheet will require slightly higher temperatures when heated. Armourplast ™ Classic IKO’s base sheet is APP.
Hybrid IKO offers hybrid bituminous roofing systems, which typically combine built-up roofing plays with a modified cap sheet. Specification requirements will determine which products are best suited to achieve desired performance. Hybrid systems that are properly applied offer excellent weatherproofing.
This post was written by professionals at Commercial Roof Services. Commercial Roof Services takes immense pride in being a leading Commercial Roofing Miami Gardens, FL and industrial roofing company dedicated to providing top-tier roofing solutions for businesses and industries of all sizes. With a proven track record and a team of highly skilled professionals, CRS has become a go-to choice for clients seeking unmatched roofing services.
