Tar and gravel is the oldest flat roof system still being installed in Texas, and owners keep asking whether it belongs on a 2026 building or in a museum. The honest answer is that it depends far less on the roof than on the building underneath it. Here is how we decide.
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Is built-up roofing still a good option in 2026?
Built-up roofing is still a good option in 2026, but only for a narrow set of buildings. It earns its place on structures that can carry the weight, roofs that see constant foot traffic or equipment service, and buildings in hail country.
Single-ply membranes took most of the low-slope market over the last three decades, and for good reason. They are lighter, faster to install, cheaper per square foot, and they arrive at the job site already reflective. That shift was real, and it is not reversing.
What did not happen is BUR disappearing. It is still a code-compliant, warrantable, Class A system with a hundred-year performance record. The useful question is not whether built-up roofing is good. It is whether your building is a built-up roofing building. Most in Texas are not. Some very much are.
What is a built-up roof made of?
A built-up roof is a membrane assembled on site from alternating layers of hot bitumen and reinforcing felt. A typical system is a base sheet, three or four plies of fiberglass felt, and a surfacing layer of either gravel set in a flood coat of asphalt or a granule-surfaced cap sheet.
The redundancy is the whole point. A single-ply roof has one waterproofing layer and a seam network. A four-ply BUR has four, bonded into one mass. Puncture one ply and there are three more underneath.
If you have been told BUR is obsolete, it is worth knowing that four-ply aggregate-surfaced built-up roofing is still written into the federal Unified Facilities Guide Specifications used by the Army Corps of Engineers, NAVFAC, the Air Force and NASA, for slopes from a quarter inch to three inches per foot. That specification also requires a twenty-year no-dollar-limit manufacturer warranty on larger and mission-critical roofs. Systems that are genuinely obsolete do not stay in federal construction criteria.
How long does a built-up roof last in Texas?
A properly installed built-up roof commonly runs twenty to thirty years in Texas, and aggregate-surfaced systems on well-drained decks sometimes go longer. Age is a poor predictor on its own. Drainage, deck type and flood coat condition decide the outcome.
Heat is the variable most Texas owners underestimate. Asphalt is graded by softening point, and the same federal specification directs designers toward the hardest grade, Type IV, in locations where ambient temperature frequently exceeds 100 degrees. Specify a softer grade on a West Texas roof and the bitumen will creep on the slopes and bleed at the laps long before the felts wear out.
The other killer is standing water. Asphalt BUR needs positive drainage because ponding leaches the oils out of the bitumen and leaves the membrane dry and cracked exactly where water sits longest. If your roof holds water 48 hours after a storm, that is a drainage project first and a roofing project second.
Does gravel BUR handle hail better than single-ply?
Aggregate surfacing genuinely does improve hail resistance, and it is one of the few claims in roofing with federal test data behind it. In ice-sphere impact testing, a slag-surfaced built-up roof took no membrane damage from stones up to two and a half inches, while smooth-surfaced BUR cracked at two inches.
Those figures come from the National Bureau of Standards, now NIST, which fired cast ice spheres at roof assemblies at free-fall terminal velocity and recorded what broke. The published hail resistance testing of roofing products found that the aggregate absorbed the impact by scattering, leaving nests in the stone instead of fractures in the felts.
Two findings in that report matter more than the headline number, and almost nobody quotes them. First, what sits under the membrane matters as much as what sits on top. The same assembly that survived two and a half inch stones over a dense deck cracked at one and three quarter inches when it was laid over soft insulation. Second, coal tar pitch systems cracked at every hailstone size tested, because coal tar is more brittle than asphalt.
Be fair about the limits of this. The testing dates to 1969, single-ply formulations have improved substantially since, and modern impact-rated membranes are a serious option in hail country. If hail is your driving concern, the more useful lever in 2026 is usually a tested assembly rather than a system category, which is why we point owners toward FM Global approved roofing assemblies and cover board.
Will a new built-up roof pass the energy code in Texas?
A dark aggregate roof does not meet the prescriptive reflectance requirement in most Texas jurisdictions, so it has to reach compliance another way. That is a solvable design problem, but it needs solving before the bid, not after plan review.
Most of the state sits in Climate Zone 2 or 3, and the 2021 International Energy Conservation Code requires low-slope roofs over cooled conditioned space in those zones to hit a three-year aged solar reflectance of 0.55 with an aged thermal emittance of 0.75, or an aged solar reflectance index of 64. The City of Lubbock adopted the 2021 IECC by ordinance in March 2024 and did not amend that section, so it applies as written here. The Panhandle, in Zone 4, falls outside the requirement.
There is a ballast exception, but it does not rescue a normal gravel roof. It requires at least 17 pounds per square foot of stone, and standard BUR aggregate is applied at roughly a tenth of that. The realistic compliance routes are a reflective granule-surfaced cap sheet instead of gravel, a reflective top coating over the flood coat, or the insulation and whole-building performance paths.
This is also where the operating cost conversation belongs. If your goal is lower summer load rather than maximum durability, look at ENERGY STAR roof certification in Texas and at how a new commercial roof lowers energy bills before you settle on a system.
Is a built-up roof too heavy for your building?
Weight is the most common reason a built-up roof gets ruled out, and it is a structural question, not a roofing question. Surfacing alone adds roughly 60 pounds of flood coat and 400 pounds of gravel per hundred square feet, before any plies, insulation or existing layers.
That is around four and a half pounds per square foot of dead load added to the deck. On a 1970s concrete or heavy timber structure it is a non-issue. On a lightweight steel deck with long bar joist spans, or on any building already carrying an old roof that was recovered once, it needs an engineer’s sign-off rather than a roofer’s opinion.
The same weight shows up again at the end of the roof’s life. Gravel tear-off is slow, dirty and expensive, and disposal volume is high. Price that into the twenty-year number, not just the installation.
BUR compared with the systems it competes against
| Factor | Built-up (aggregate) | Modified bitumen | TPO / PVC single-ply |
| Hail behavior | Aggregate absorbs impact, damage often hidden | Good with polyester reinforcement | Depends heavily on cover board and rating |
| Load on deck | Highest | Moderate | Lowest |
| Energy code path in Zones 2 and 3 | Needs cap sheet, coating or performance path | Reflective cap sheet available | Meets it off the roll in white |
| Foot traffic and equipment | Excellent | Very good | Needs walk pads and care |
| Leak location and repair | Hardest, gravel hides the source | Straightforward | Easiest, heat weld patch |
| Tear-off burden | Heavy and costly | Moderate | Light |
| Best fit | Heavy structures, industrial roofs, service traffic | Most West Texas re-roofs | Cooling-driven buildings, weight-limited decks |
For most Texas re-roofs the practical middle ground is modified bitumen roofing in West Texas, which keeps multi-layer redundancy without the gravel. If reflectivity and speed matter more, compare TPO roofing and TPO vs EPDM before deciding.
When is built-up roofing the wrong choice?
Rule BUR out when the building is occupied and sensitive to fumes, when wind can scour the aggregate, when the deck cannot carry the load, or when the roof is headed for equipment or solar in the next few years.
Hot asphalt application means kettles, open flame and fumes near air intakes. On a hospital, school, restaurant or occupied office, that alone often ends the conversation. Federal criteria go further and direct designers to use a granule cap sheet instead of gravel wherever wind-blown aggregate could put property or people at risk. In a market with our wind, parapet height and roof edge detailing decide whether loose stone stays put.
Two more disqualifiers come up regularly. Gravel makes leak tracing genuinely difficult, since water travels between plies and surfaces far from the breach, which is why infrared thermal roof inspection earns its cost on these roofs. And if you are planning to install solar panels on a commercial flat roof, racking, ballast and future roof access all get complicated on an aggregate surface.
You already have a built-up roof. Repair, recover, or replace?
Base this decision on core samples and moisture scanning, not on the roof’s age. If the insulation is dry and the failures are at flashings and penetrations, repair or restore. If the insulation is wet across a meaningful share of the roof, replace it.
Wet insulation is the deciding factor because it never dries out, it destroys R-value permanently, and it corrodes steel deck underneath. Coating over it just buys a warranty on a saturated assembly. Cutting cores and running a moisture scan costs a fraction of a re-roof and settles the argument with facts.
On a sound old gravel roof, restoration is often the better economics, and the trade-offs are worth reading in commercial roof coating vs replacement. Also check the details before you commit, because on most aged BUR roofs the leaks are not in the field at all. They are at flashings and HVAC curb flashings.
Frequently asked questions
Can you install a TPO roof over an existing gravel roof?
Yes, but the gravel has to be removed or spudded and a cover board installed first, which erases much of the cost savings of a recover. Verify the existing insulation is dry before committing, because a recover locks that moisture in permanently.
Can you still get a manufacturer warranty on a new BUR system?
Yes. Major manufacturers still issue no-dollar-limit warranties on built-up systems, typically ten to twenty years, provided an approved applicator installs the full assembly.
Is coal tar pitch roofing still available?
It is still manufactured and remains the only membrane the building code recognizes for dead-level slopes, but it is rare and specialized in Texas. Its brittleness in impact and the handling requirements make it a poor default choice here.
How much does a built-up roof cost compared with single-ply?
Installed cost per square foot generally runs above single-ply, and the gap widens once tear-off and disposal of the old system are included. Get the deck load and drainage evaluated first, since either one can change the system before price does.
The short version
Built-up roofing in 2026 is a specialist choice, not a default one. It still makes sense on heavy structures, industrial roofs and buildings that see constant rooftop traffic, and its aggregate surfacing carries real hail performance behind it. For most Texas commercial buildings, a modified bitumen or single-ply assembly will serve better for less weight and less money.
If you are weighing a re-roof, start with core samples, a moisture scan and a look at the deck capacity. Choose the roofing contractor before the roofing system, and read how to choose the right commercial roofing contractor in Texas if you are gathering bids.
