Built-up roofing, the layered asphalt-and-felt system with a gravel or mineral cap, is still up on plenty of older buildings around downtown Evansville and the University of Evansville campus. It's an older technology, but a properly maintained BUR roof has a real service life left in it, and we still recommend it in specific situations.
Older downtown commercial buildings, many built long before single-ply membranes existed, often carry an original or once-replaced BUR system. On buildings where the structure and deck are sound but budget doesn't stretch to a full modern membrane conversion, a properly detailed BUR recover or replacement is a legitimate option, not a compromise.
Some institutional buildings around the university campuses in this region also still run BUR on original sections, particularly where the roof structure was built to carry the extra weight of a multi-ply gravel system and converting to a lighter membrane isn't necessary.
Some manufacturing buildings from earlier construction eras also carry original BUR sections that have simply never needed full replacement, maintained instead through periodic gravel top-ups and localized ply repairs rather than a wholesale reroof.
A BUR system layers multiple plies of asphalt-saturated felt or fiberglass, each mopped down with hot or cold asphalt, finished with either a smooth cap sheet or a gravel and mineral surface. The number of plies, typically three or four, is a real cost and durability variable, and a contractor who won't specify ply count in writing is leaving room to cut it without you knowing.
The gravel or mineral cap does double duty. It protects the asphalt layers underneath from direct UV exposure, and its weight adds a degree of wind resistance that matters on a roof exposed to the straight-line wind events this region sees during spring and fall storm season.
Base sheet attachment method, whether nailed, mopped, or mechanically fastened to the deck, is another variable that affects both cost and wind performance, and it's worth confirming in writing alongside ply count rather than assuming a standard approach applies to every deck type.
Southern Indiana sits close enough to active severe-weather corridors that wind uplift is a real design consideration, not a formality. A properly installed BUR system, with adequate ballast weight and correctly detailed edge metal and parapet flashing, resists uplift better at the perimeter than some lighter membrane systems do without added fastening.
We pay particular attention to parapet cap flashing on BUR roofs specifically, since a lifted parapet cap during a wind event can pull the membrane's edge termination loose even when the field itself holds up fine.
The perimeter and corners of any flat roof take the highest wind load during a storm, which is where BUR failures we inspect after severe weather events tend to start. On a BUR project we confirm:
Southern Indiana's humid summers create a real blistering risk on BUR roofs, where trapped moisture between plies expands under heat and lifts the surface. Small blisters aren't always urgent, but they're worth tracking on a regular inspection schedule since a blister that ruptures opens a direct path for water into the plies below.
Regular gravel maintenance also matters more than owners tend to expect. Gravel can shift or thin over time from foot traffic and wind, exposing asphalt underneath to UV it wasn't built to handle long-term.
A BUR roof rewards regular attention more than it punishes neglect immediately, which can create a false sense of security. Small issues, a thin gravel spot, a minor blister, an edge seam starting to lift, are inexpensive to address individually but compound if left across multiple seasons.
We recommend at minimum a spring and fall walk on any BUR roof still in active service, timed around the region's two severe-weather seasons so problems get caught before the next round of storms rather than after. A written record from each walk also gives an owner a real maintenance history to reference when budgeting for eventual replacement.
It's an older technology, but a properly maintained BUR system still performs well, especially on buildings where the structure was designed to carry the ballast weight.
It depends on the building's exposure and budget, and we'll put that number in writing rather than leaving it as a vague line item.
Sometimes, if a moisture scan shows the existing plies and deck are dry and sound, and local code allows another layer.
Trapped moisture between plies expanding under summer heat. We track blister size and location on inspections rather than treating every blister as an emergency.
Yes, ballast weight adds meaningful wind resistance, particularly at the roof perimeter where uplift forces concentrate during a storm.