If you own a commercial building or a home with a flat or low-slope roof, you’ve probably heard the term “build up roofing.” Often shortened to BUR, it’s one of the oldest and most proven flat roofing systems in use. Here is how it works, where it fits, and what to weigh before choosing it.
Build Up Roofing Explained
Build up roofing is a multi-layer system made of alternating layers of waterproofing material and reinforcing fabric. Installers apply hot asphalt, coal tar, or cold-applied adhesive between layers of roofing felt (also called ply sheets). The result is a thick, continuous membrane that is often called “tar and gravel” because of the stone surfacing on top.
A typical system includes:
- Base layer: A base sheet that sits on the roof deck or insulation.
- Reinforcing plies: Usually two to four layers of fiberglass or organic felt, each bonded with asphalt or tar.
- Surfacing layer: Gravel, mineral cap sheet, or a reflective coating that protects the plies from sun, wind, and foot traffic.
Because the layers overlap and bond to each other, a flaw in one layer rarely ruins the whole system. That redundancy is why BUR has a long track record on flat roofs.
Where Build Up Roofing Works Best
BUR is designed for flat and low-slope roofs, so you’ll see it most on commercial buildings, warehouses, schools, and apartment complexes. Some homeowners use it on flat additions, porches, or low-pitch sections. It isn’t suited to steep-slope roofs. Those are better served by shingles or metal, which you can learn about on our shingle roofing page.
Benefits of Build Up Roofing
Durability: With proper installation and upkeep, BUR commonly lasts 20 to 30 years.
Waterproofing: The layered membrane handles standing water better than many single-layer systems, which matters during Florida’s heavy summer rains.
Foot-traffic tolerance: The surfacing layer holds up when HVAC technicians or maintenance crews need to walk the roof.
Added protection: Multiple plies provide insulation value and a buffer against hail, debris, and UV exposure.
Repairability: Damaged areas can usually be patched without replacing the entire roof.
Drawbacks to Consider
No roofing system is perfect. BUR is heavy, so your structure must be able to support it. Installation, especially hot-applied asphalt, involves fumes and safety precautions, which is why it should be left to trained professionals. The system can also be less flexible than modern membranes, and newer options like TPO or modified bitumen may be quicker to install. For some buildings, those are the better fit.
How Much Does It Cost?
Pricing depends on roof size, number of plies, insulation, accessibility, and the condition of the existing deck. BUR often costs more up front than some single-ply membranes but can pay off through its lifespan. The most reliable way to get a real number is a professional inspection.
Keeping a BUR System in Shape
Regular care extends the life of any flat roof. Clear debris and standing water, check seams and flashing, and look for blisters, cracks, or exposed felt. An annual roof inspection after storm season helps you catch small issues early, and prompt roof repairs keep minor leaks from turning into costly deck damage.
Talk to Tallahassee’s Roofing and Gutter Specialists
If you manage a flat-roofed property and wonder whether build up roofing is right for you, GutterHawk can help. With over 20 years serving Tallahassee, we handle everything from inspections to full installations, and we offer free estimates. Explore our commercial roofing services, or call us at 850-779-1081 to schedule a visit.
Frequently Asked Questions
BUR stands for “built-up roofing,” the layered flat roofing system made of alternating bitumen and reinforcing felt plies.
Most last 20 to 30 years, depending on installation quality, climate, and maintenance.
It can perform well because its layered, waterproof membrane resists ponding water, though drainage and regular inspections are important in heavy-rain regions.
Often, yes. Blisters, cracks, and damaged flashing can usually be repaired. A professional inspection will tell you whether repair or replacement makes more sense.
BUR uses multiple on-site layers of felt and asphalt or tar. Modified bitumen is a factory-made sheet with polymers added for flexibility, typically installed in fewer layers.