Built-Up Composition Roof (also called BUR) remains a durable and cost-effective choice for low-slope commercial and residential roofs. This article explains materials, installation, maintenance, costs, and pros and cons to help property owners and facility managers make informed decisions.
| Aspect | Key Takeaway |
|---|---|
| Materials | Multiple layers of felt and bitumen with surfacing |
| Typical Lifespan | 20–35 Years With Proper Maintenance |
| Best Use | Low-Slope Commercial Or Multi-Unit Residential Roofs |
| Average Cost | Moderate — Varies By Location And Layers |
What Is A Built-Up Composition Roof?
A Built-Up Composition Roof (BUR) is a layered roofing system composed of alternating plies of roofing felt and bitumen, finished with a protective surfacing such as gravel, slag, or a coating.
The system is installed on low-slope or flat roofs, creating multiple waterproof layers that resist punctures, UV, and weathering.
Components And Materials
Primary components of a BUR include bitumen (asphalt or coal tar), roofing felt or fiberglass felts, and a surfacing layer. Each component contributes to waterproofing, structural integrity, and UV protection.
Bitumen Types
Asphalt is the most common bitumen for BUR, offering good adhesion and flexibility. Coal tar pitch is more resistant to oils and chemicals but has environmental and odor considerations.
Reinforcement Felts
Felt layers are made from organic fibers or fiberglass. Fiberglass felts
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Surfacing Options
Common surfacings include embedment of aggregate like gravel or slag, mineral-surfaced cap sheets, and reflective coatings. Gravel ballast
How Built-Up Composition Roofs Are Installed
BUR installation involves multiple steps: substrate preparation, vapor barrier or insulation placement, hot mopping or cold adhesive application of bitumen, layering felts, and final surfacing application.
- Deck Preparation: Clean, dry deck free of debris; repair any structural issues.
- Vapor Barrier/Insulation: Install insulation and secure per design to prevent condensation and thermal movement.
- Base Sheets: Apply the first felt layer embedded in hot bitumen or cold adhesive.
- Plies: Add two or more additional plies of felt and bitumen to achieve specified thickness and performance.
- Cap Sheet/Surfacing: Finish with gravel, mineral cap sheet, or coating to protect from UV and mechanical wear.
Advantages Of Built-Up Composition Roofs
Durability is the hallmark of BUR systems; multiple plies offer redundancy so punctures seldom cause immediate leaks.
BUR provides excellent waterproofing, thermal mass benefits from ballast, and proven fire resistance when mineral-surfaced or gravel is used.
Limitations And Considerations
Installation of traditional BUR often requires hot asphalt mopping, which raises concerns about fumes, fire risk, and requires skilled applicators. Weight of gravel-balled BUR may require structural assessment.
BUR can be more difficult to repair neatly compared with single-ply membranes for localized damage, though repairs are still straightforward for experienced contractors.
Maintenance Best Practices
Regular inspections increase service life. Suggested intervals include semi-annual inspections and after major storms. Focus on flashings, drains, and seams where water commonly infiltrates.
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- Keep drains and scuppers clear to avoid standing water.
- Remove debris and vegetation that can trap moisture.
- Inspect and reseal flashings, counterflashing, and penetrations annually.
- Replace or replenish gravel surfacing where loss exposes membrane.
Common Repairs And Patch Techniques
Minor punctures and seam failures are typically repaired using compatible bitumen, new felt patches, and proper embedment. Surface blisters
For widespread deterioration, roof resurfacing or a full tear-off may be more cost-effective than repeated patches.
Comparing Built-Up Composition Roofs To Other Systems
| Feature | Built-Up Roof (BUR) | Single-Ply Membranes |
|---|---|---|
| Durability | High, Multiple Layers | Good To High, Depends On Membrane |
| Installation | Labor-Intensive, May Use Hot Asphalt | Quicker, Often Mechanically Attached Or Adhered |
| Weight | Heavy (Gravel Ballast) | Lightweight |
| Repairability | Repairable But Less Neat | Easy To Patch Seam Areas |
Cost Factors And Lifespan
BUR costs vary by region, roof complexity, number of plies, and surfacing type. Initial cost is moderate
With routine maintenance, a well-installed BUR can last 20 to 35 years
When To Choose Built-Up Composition Roofing
BUR is recommended for low-slope commercial buildings, warehouses, and residential flat roofs that need proven waterproofing and fire resistance. It suits owners prioritizing longevity and redundancy over lightweight installation.
It is less suited for roofs where weight is restricted or where rapid, low-odor installation is required.
Energy Efficiency And Cool Roof Options
Traditional BUR with dark surfacing absorbs heat, but reflective coatings and light-colored cap sheets can transform a BUR into a cool roof, improving energy performance and reducing cooling load.
Adding insulation beneath the BUR also increases thermal performance, reduces HVAC costs, and mitigates condensation risks.
Code, Safety, And Environmental Considerations
Local building codes often specify fire performance, ballast requirements, and slope tolerances for BUR. Proper permitting and compliance
Environmental factors include fume control during hot mopping and proper disposal of removed roofing materials. Recycled aggregate and low-VOC coatings can reduce environmental impact.
Selecting A Contractor And Warranty Options
Choose contractors with BUR-specific experience, licensed credentials, and references. Request examples of completed BUR projects and details on warrantee coverage.
Warranties vary: manufacturer warranties may cover materials, while installer warranties cover workmanship. Combined warranties provide the best protection
Signs It May Be Time To Replace A BUR
- Chronic leaks despite repeated repairs.
- Significant loss of gravel or surfacing exposing felt.
- Widespread blistering, splitting, or multiple damaged plies.
- Roof age beyond expected lifespan with increased maintenance costs.
Retrofitting And Overlay Options
In some cases, BUR can be overlaid with a new BUR cap sheet or converted to a single-ply system depending on substrate and structural capacity. Overlay work can save tear-off costs
Consultation with a roofing engineer will determine suitability for overlays or hybrid solutions combining BUR with modern membranes or coatings.
Frequently Asked Questions
Is A Built-Up Roof Fire Resistant?
When finished with mineral-surfaced cap sheets or gravel, BUR provides strong fire resistance. Coal tar pitch systems historically had better flame resistance
Can BUR Be Installed Without Hot Asphalt?
Yes, cold-applied adhesives and modern cold-process systems reduce fume and fire risk, though traditional hot mopping remains common for certain project requirements.
How Long Should Maintenance Take Each Year?
Annual inspections with minor repairs typically require a few hours for a commercial roof of moderate size; severe issues will demand more time and budget.
Key Takeaways For Property Managers
Built-Up Composition Roofs Offer Proven Longevity, Redundancy, And Strong Waterproofing for low-slope buildings, provided proper installation and routine maintenance are observed.
Consider structural load, local climate, code requirements, and long-term lifecycle costs when specifying BUR versus alternative roofing systems.
For tailored assessments, engaging a qualified roofing contractor or building envelope consultant ensures the right balance of performance, cost, and longevity for each property.
How to Get the Best Roofing Quotes
- Prioritize Workmanship
A roof is one of your home’s most important investments. Always choose a contractor based on experience and reputation — not just price. Poor installation can lead to expensive problems down the road. - Compare Multiple Estimates
Don’t settle for the first quote you receive. It’s always a smart move to compare at least three bids from local roofing professionals. You can 877-801-4315 to get local quotes from roofing contractors in your area, available across the United States. - Use Negotiation Tactics
After selecting a trusted roofer, be sure to use our proven tips — How to Negotiate with Roofing Contractors — to secure the best possible final price without cutting corners.