# Built-Up Roofing (BUR)

Built-up roofing is the oldest of the modern methods, dating to the early 1800s — and still the system Lloyd Roofing applies most. A roof that is literally built by adding layers.

**Provider:** Lloyd Roofing Company, Inc., Greenwood SC. Commercial and industrial only. 1-800-421-3830.

- **Typical life:** 10 – 20 years
- **Plies:** 2 · 3 · 4
- **Surfacing:** Gravel · coating · mineral

## How a built-up roof works

Formerly the membrane was the waterproofing agent and the bitumen was the adhesive. With the advent of synthetic fibers the roles reversed: today the bitumen is the waterproofing agent and the membrane holds it in place.Built-up roofs can be installed with coal tar pitch, asphalt, cold-application adhesive or modified asphalt. Every system uses some combination of base sheet, ply sheets (felts) and cap sheet, then a surfacing: gravel, asphalt, coatings or mineral granules.

## Reinforcement: what's between the bitumen

### Glass-fiber mats
Glass-fiber redefined the built-up roof and has almost completely replaced organic felt across the United States. It reduces blistering and ridging, and unlike organic felt it does not absorb water — so moisture doesn't get trapped in a new roof system.
### Organic felts
Cellulose fibers, shredded wood and felted papers. Susceptible to water absorption, which leads to increased blistering and ridging.
### Saturated, coated and mineral-surfaced sheets
Saturated felts are bitumen-impregnated and generally serve as base sheets. Coated felts add finely ground minerals for durability and cold-weather resistance. Mineral-surfaced sheets take that a step further, embedding granules in the topside — the cap sheet.

## The bitumens

- Asphalt — the dense residue left from petroleum distillation. Types run from I (dead level) to IV (special steep). Generally Type II in the field of the roof and Type III on penetrations and base flashings.- Coal tar pitch — distilled from high-temperature coke oven tar. Naturally resistant to temperature change, water, moisture and vapor transmission. Its low melt point makes it self-healing. It must be surfaced with gravel to hold the bitumen in place, and is not recommended above ½" in 12" slope.- Cold process — an inexpensive tar/asphalt semi-liquid, applied by brush or roller. Used mainly on smaller jobs where a more substantial roof isn't required.

## Frequently asked questions

**How long does a built-up roof last?**

Each ply is said to represent roughly five years of service — a 3-ply roof indicates a 15-year system and a 4-ply a 20-year system. That holds only if the roof is properly installed and maintained across its life span.

**Is BUR better than single-ply?**

They solve different problems. A built-up roof gives you multiple redundant layers of waterproofing; a single-ply gives you one, installed faster and lighter. For buildings where a leak is expensive — healthcare, institutional, industrial — the redundancy of BUR is usually worth its cost.

**What is the difference between asphalt and coal tar pitch?**

Asphalt is the residue of petroleum distillation. Coal tar pitch comes from coke oven tar and has a low melt point that lets it self-heal minor splits. Coal tar must be gravel-surfaced and is limited to very low slopes.

**Can a built-up roof be recovered instead of torn off?**

Sometimes. It depends on the condition of the insulation and deck, the number of existing roof layers, and local code. Lloyd Roofing assesses the whole assembly before recommending recover versus tear-off.


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**Lloyd Roofing Company, Inc.** · 2415 Montague Avenue Ext., Greenwood, SC 29649 · 1-800-421-3830 · Mon–Thu 7:00am – 5:00pm · Fri 7:00am – 12:00pm
Commercial and industrial roofing only. Serving South Carolina, North Carolina and Georgia since 1965.
SC contractor license CLG10175 · USDOT 483661