Built-up roofing, often called BUR, is a traditional flat roofing system consisting of multiple alternating layers of asphalt or coal tar and reinforcing felt, built up in sequence directly on the roof deck to create a thick, durable, multi-ply waterproof membrane.
This layered approach, with each successive layer adding redundancy to the overall waterproofing system, has been used reliably for well over a century, representing one of the oldest continuously used flat roofing techniques still in practice today.
The finished surface is typically topped with a layer of gravel or a reflective coating, both protecting the underlying layers from UV degradation and providing additional weight to help hold the system in place.
What Does Built-Up Roofing Involve?
- Multiple alternating layers of asphalt and reinforcing felt
- Sequential installation building up thickness on site
- A gravel or reflective coating surface layer
- Substantial total system weight compared to single-ply membranes
Why Is Built-Up Roofing Important?
The redundancy inherent in multiple overlapping layers gives built-up roofing genuine long-term reliability, with a well-installed system capable of lasting several decades, a proven track record that has sustained this traditional technique’s relevance even as newer single-ply membrane alternatives have gained market share. This layered redundancy remains a genuine performance advantage some building owners specifically value.
Because installation involves sequential, labor-intensive application of multiple layers, often using hot asphalt requiring specialized equipment and safety precautions, built-up roofing typically takes longer to install and may cost more in labor than a comparable single-ply membrane system. This tradeoff between upfront labor cost and long-term reliability is worth discussing with a roofing contractor. This consideration helps building owners weigh upfront cost against long-term system reliability.
Built-Up Roofing vs. BUR Roofing
These terms describe the identical roofing system, with BUR being simply the common industry abbreviation for built-up roofing, used interchangeably in most professional and everyday contexts.