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Commercial · Traditional BUR Systems

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Built-up roofing (BUR) — alternating layers of bitumen and reinforcing fabric topped with gravel or a cap sheet — has been the workhorse of commercial flat-roof systems for over a century.

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Built-Up Roofing San Jose

Built-Up Roofing
Done Right Since 1952

Built-up roofing (BUR) — alternating layers of bitumen and reinforcing fabric topped with gravel or a cap sheet — has been the workhorse of commercial flat-roof systems for over a century. While single-ply systems (TPO, EPDM) have taken the larger share of new commercial installations, BUR remains the right answer for specific applications: long-lifespan durability requirements, high foot-traffic roofs, certain retrofit scenarios, and some historical or preservation contexts. Keith Roofing has been installing BUR since the 1950s and we still do BUR work when it's the right technical answer.

BUR is a time-proven system. Installed properly, BUR regularly delivers 25-35+ years of service life. The multi-ply structure provides redundancy — multiple waterproof layers rather than a single membrane. The gravel or cap-sheet surface provides UV protection and extends field membrane life. For high-wear applications where single-ply membranes can suffer punctures, BUR's robustness matters.

Our BUR work covers: new BUR installation on appropriate commercial projects; BUR replacement for end-of-life systems where BUR makes sense for the replacement (often matching existing for consistency); BUR repair for localized failures; and evaluation of existing BUR for either continued service, coating restoration, or replacement to single-ply.

Built-Up Roofing project by Keith Roofing Company in San Jose
Complete Guide

Understanding BUR Systems

The Structure of a BUR System

A traditional BUR system has several components: base sheet (mechanically fastened or adhered layer directly on the deck or insulation); ply sheets (multiple layers of reinforcing fabric — originally asphalt-saturated felt, now often fiberglass — installed between layers of hot asphalt or cold-applied adhesive); flood coat (final layer of hot asphalt over the top ply sheet); and surfacing (mineral-surfaced cap sheet, loose-laid gravel, or other protective surface).

The multi-ply structure provides redundancy — water breaching one layer must also breach subsequent layers to cause interior damage. The gravel or cap sheet surfacing protects the flood coat from UV degradation and impact damage.

When BUR Makes Sense

BUR is the right choice when: long-term durability is prioritized over initial cost (BUR typically outlasts single-ply systems when properly installed); high foot traffic is expected (BUR gravel surface handles wear better than single-ply membranes); retrofitting existing BUR where matching the existing system for consistency makes sense; and specialty applications like some historical preservation work or specific commercial requirements.

BUR is not the right choice for most modern new construction commercial work — TPO or EPDM typically deliver comparable performance at lower cost and with better energy characteristics (particularly for Title 24 cool-roof compliance).

BUR Installation Process

BUR installation is labor-intensive and requires specialized equipment. Hot-applied BUR uses melted asphalt (typically in a kettle or tanker on-site) applied between ply sheets. This is the traditional method and provides the strongest bond but requires specialized equipment and operator training. Cold-applied BUR uses liquid-applied cold adhesive between plies — simpler and safer but sometimes delivers slightly reduced performance.

Proper BUR installation requires: appropriate insulation and cover board (same as single-ply systems), mechanically-fastened or adhered base sheet, ply sheets installed with proper asphalt application temperatures and coverage rates, flood coat at specified thickness, and gravel or cap sheet surfacing at proper coverage. Flashings at all penetrations must be detailed with compatible BUR flashing materials.

When to Consider

Signs You Need
Built-Up Roofing

01

Existing BUR at End of Service Life

30+ year old BUR systems showing widespread deterioration typically need replacement. Decision: another BUR system, conversion to single-ply, or coating restoration.

02

High Foot-Traffic Application

Buildings with significant rooftop foot traffic (HVAC service, rooftop equipment, occupied rooftop space) benefit from BUR durability.

03

Preservation/Historical Consistency

Some historical or preservation contexts benefit from maintaining existing BUR system type rather than converting to modern alternatives.

04

Long-Term Hold Commercial Property

Owners planning multi-decade hold periods may benefit from BUR's long service life despite higher upfront cost.

05

Specific Technical Requirement

Some applications have specific technical requirements (chemical exposure, mechanical wear, code requirements) that favor BUR over single-ply alternatives.

06

Retrofit Matching Existing

Repair and partial replacement scenarios often benefit from matching existing BUR for consistency and proper interface at transitions.

BUR Systems

Built-Up Roof
Options

GAF BUR Systems

Industry-leading BUR product line with extensive accessories and warranty programs.

Johns Manville BUR

Traditional BUR with solid Bay Area distribution. Reliable performance across decades of use.

Hot-Applied Asphalt

Type III or Type IV asphalt kept molten in on-site kettles during installation. Temperature-controlled for proper application and cure.

Ply Sheets (Fiberglass)

Modern BUR typically uses fiberglass reinforcement ply sheets rather than traditional asphalt-saturated felt. Better durability and moisture resistance.

Mineral-Surfaced Cap Sheet

Cap sheet option for BUR systems — smoother aesthetic than gravel surface, easier long-term maintenance.

Surfacing Aggregate

Loose-laid stone gravel for traditional BUR aesthetic. Various sizes and colors available.

Our Process

How We Handle
Your Built-Up Roofing

01

System Design & Deck Review

BUR is heavy — structural capacity must support the system. We verify deck capacity and recommend engineering review if needed.

02

Insulation & Base Sheet

Polyiso insulation installation, cover board, mechanically-fastened or adhered base sheet.

03

Ply Sheet Installation

Multiple plies installed with hot asphalt (or cold-applied adhesive). Proper asphalt temperature, application coverage, and ply overlap critical for performance.

04

Flood Coat & Surfacing

Final flood coat of hot asphalt, then surfacing (gravel or cap sheet). Surfacing coverage rate matters for UV protection and long-term performance.

05

Flashings & Final Inspection

Flashings at all penetrations using BUR-compatible materials. Final inspection for complete coverage and proper detailing.

Why Keith Roofing

Why Homeowners Choose Us
for Built-Up Roofing

01

70+ Years of BUR Experience

We've been installing BUR since mid-century. That experience delivers proper technique, realistic performance expectations, and pattern recognition for what works long-term.

02

Hot-Applied Equipment & Training

Hot-applied BUR requires specialized equipment (kettles) and operator training. We maintain the equipment and crew capability for this work.

03

Honest System Recommendation

Most modern commercial projects are better served by single-ply systems. We tell you honestly when BUR is the right answer and when another system would serve better.

04

Historical Repair Capability

For aging BUR systems still serving buildings, we do proper repair work that extends life rather than forcing replacement. BUR often has more remaining life than contractors without BUR experience assume.

Industrial Building — BUR Replacement Matching Existing — Keith Roofing Company case study
Featured Project

Industrial Building — BUR Replacement Matching Existing

Milpitas Industrial

A 65,000 sq ft industrial building in Milpitas with a 1985 BUR roof at end-of-service required replacement. Owner evaluated TPO conversion vs. another BUR system. Decision factors: existing rooftop equipment staging required foot-traffic tolerance throughout the building's operational life, and two adjacent buildings on the property retained BUR — maintaining system consistency simplified long-term maintenance. We installed a new GAF BUR system matching the existing configuration: polyiso insulation to current Title 24 R-value, mechanically-fastened base sheet, 3-ply hot-applied fiberglass ply sheets, flood coat, and mineral-surfaced cap sheet. Project completed over 4 weeks. Expected service life: 30+ years.

Built-Up Roofing Portfolio

Recent Built-Up Roofing
Projects

Keith Roofing Built-Up Roofing project 1
Keith Roofing Built-Up Roofing project 2
Keith Roofing Built-Up Roofing project 3
Keith Roofing Built-Up Roofing project 4
Common Questions

Built-Up Roofing
Answered

No, though it's less common for new commercial installations than single-ply systems. BUR still performs well for specific applications — high foot traffic, long-term durability requirements, some retrofit scenarios, and certain specialty projects.
Properly installed BUR regularly lasts 25-35+ years. Some 40+ year BUR roofs are still in service. Main failure modes are usually flashings and surface deterioration rather than field membrane issues.
Usually comparable or slightly higher per square foot installed. Total cost of ownership over the roof's lifespan depends on application and service life.
Often yes. BUR is well-suited to localized repair — seam restoration, flashing renewal, patch repairs all work well. A BUR in otherwise-sound condition often has more remaining life than you'd think.
Gravel-surfaced BUR has loose stone over the flood coat — traditional appearance, excellent UV protection, but can complicate maintenance and drain maintenance. Cap-sheet BUR uses a mineral-surfaced final ply — cleaner appearance, easier maintenance, typical choice for modern BUR work.
Commercial re-roof projects in California must meet Title 24. BUR with white surfacing (coated cap sheet or reflective coating application) meets cool-roof requirements. Traditional gravel-surfaced BUR may require alternative compliance paths or reflective coating.
Depends on application. If your building has low foot traffic, benefits from cool-roof energy performance, and you're replacing anyway, TPO is usually the better choice. If high foot traffic is a factor or matching existing system matters, another BUR may be right.
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