Built-up roofing is one of the oldest flat (low-slope) roofing type because it is proven to be a durable roofing system. There are still BUR roofs today that were originally constructed in the 1900s, and there are also new BUR still being built today despite the rise of other popular roofing materials (like TPO and EPDM).
Built-up roofs start at the roof deck (either metal, concrete, or wood), add a layer of insulation based on local building code, and are then “built-up” from there. The roofing material itself consists of layers (“plies”) of waterproof material, usually felt/tar paper, with hot tar applied in between the plies. A typical BUR system includes four plies, but can be less or more based on the building needs and property owner’s budget. It is common to add a layer of gravel rock on top of the final layer to protect the roofing system from harmful UV rays.
Pros of BUR systems
- Gravel acts as a terrific fire retardant.
- Pleasing aesthetics for windows that have a view of the roof.
- Budget-friendly, more than other flat roof systems.
Cons of BUR systems
- Very heavy weight, roof joists sometimes have to be reinforced.
- Odor and mess during installation.
- Property should be vacated during installation.
- Not a DIY project, must be done by a professional.
- Gravel can plug and clog guttering system.