Built-up Roofs / Modified Roofs
Built-up roofs (BUR’s) consist of multiple plies of roof felts laminated together with bitumen. Built-up roof material can consist of bitumen-saturated felt, coated felt, polyester felt or other fabrics. A surfacing is generally applied and can be asphalt, aggregate (gravel or slag), emulsion or a granule-surfaced cap sheet.
Built-up roofs can be installed over just about any type of roof deck as long as the proper substrate is used. BUR’s can’t be mopped to a wood roof deck. In this case a rosin sheet and base sheet are needed first. With steel roof decks, the thickness of the deck should be a minimum of 22 gauge and some type of approved insulation should be mechanically-attached to the deck to provide a substrate.
BURs are the toughest of the roofing systems. Where pedestrian traffic is high, a BUR roof system has no equal. A BUR roofing membrane is constructed on the roof by combining layers of materials (roll goods) together and in their total they act as the roofing membrane.
In the matrix of a traditional BUR membrane, tar or asphalt act as not only the glue which binds or adheres together the three to four layers of sheet-fabric roll goods, but that very tar or asphalt also acts as the main waterproofing component/ingredient which is being held/contained in place by those three to four layers of sheet-fabric. Hot tar, also known as coal-tar-pitch, has been virtually replaced by hot asphalt, but hot tar remains an outstanding product because of its ability – after it has been installed – to easily melt and flow into voids giving it the title “self-mending.”
Over the last three decades, the roofing industry has developed a variety of built-up roof types and Southern Coatings is certified to install all the various built-up materials offered by major roofing manufacturers. The key benefit to a built-up roof is the redundancy it provides due to its multiple layers. These types of roof are time-tested and most commonly used on facilities with more foot traffic or multiple penetrations on the roof.