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Flashings

Flashings are the most common source of leaks in BUR systems. You need to be careful when you are installing flashings so they will not leak. There are two kinds of flashings: vertical and horizontal. Vertical Flashings Remember that vertical means up and down. Vertical flashings are installed at upturned edges, such as walls. Cant
The first part of a vertical flashing is a cant. A cant is a triangular-shaped strip made of perlite, wood fiberboard or wood. It is used to make a smooth, angled surface from the field of the roof to the vertical surface. A Cant is adhered or mechanically fastened. Some flashing materials cannot bend very far or they will tear. You cannot install these flashing materials all the way into corners and then straight up vertical surfaces. Cants are used in corners so that flashing materials do not have to bend too far. Base Flashing The second part of a vertical flashing is called a base flashing. A base flashing is two or more plies mopped onto a vertical surface. Instead of asphalt, flashing cement may be used. Flashing cement is a special kind of asphalt roof cement. This kind of roof cement is also called mastic. A common base flashing has two parts. In the first part, the roofing felt is mopped with asphalt. For the second part, a surfacing sheet is mopped to the felts. Counterflashing The last part of a vertical flashing is called counterflashing. Counterflashing is usally made of metal. It shields the top edges and joints of the base flashing. Horizontai Flashings The second kind of flashing is horizontal. Horizontal flashings have to be installed at drains, roof edges and vents. These flashings are installed around objects on the flat surface of flashing a roof. These flashings are made of felts, asphalt, flashing cement, lead and other metals. Surfacing The third part of a BUR membrane is surfacing. There are three types of surfacing. One type is aggregate. Aggregate means gravel, crushed stone, slag or marble chips. The other two types are called cap sheets and smooth-surfaced Aggregate Aggregate surfacing is gravel, crushed stone or marble chips. This material is set in a flood coat of bitumen. Cap Sheets Cap sheets are felts coated with asphalt. When they are made at a factory, they are surfaced with mineral granules. They are usually set in hot bitumen as the final surfacing.