Commercial Roof Types: An Overview

Commercial buildings in Massachusetts and Rhode Island typically have flat or low-slope roofs that require fundamentally different waterproofing systems than residential sloped roofs. This overview covers the primary commercial roofing systems, their characteristics, and how they perform in New England.

Single-Ply Membrane Systems

Single-ply systems are now the dominant commercial roofing technology, having largely displaced built-up roofing in new construction.

EPDM (Ethylene Propylene Diene Monomer)

A synthetic rubber membrane, typically black, with the longest track record of any modern flat roofing system.

**Key specifications:**

• •Thickness: 45-mil or 60-mil (60-mil recommended for Massachusetts)
• •Seam method: Tape adhesive or liquid adhesive
• •Color: Standard black (white-coated available)
• •Lifespan: 20-30 years

**Why it works in New England:** EPDM's cold-temperature flexibility (maintaining pliability to -40°F) makes it well-suited to Massachusetts winters. The carbon black that gives EPDM its color also provides inherent UV resistance.

**Primary challenge:** Tape-bonded seams require periodic inspection. EPDM can also shrink over time, causing tension at edges and penetrations.

**Best applications:** Budget-conscious projects, cold climates, re-roofing over existing EPDM, buildings with minimal air conditioning where white color's energy benefits are less relevant.

TPO (Thermoplastic Polyolefin)

The fastest-growing commercial roofing membrane, available in white and light colors, with heat-welded seams.

**Key specifications:**

• •Thickness: 45-mil, 60-mil, or 80-mil
• •Seam method: Hot-air heat welding
• •Color: White (standard), gray, tan
• •Lifespan: 20-30 years

**Why it works in New England:** White surface reflects solar radiation, reducing cooling loads on conditioned buildings. Heat-welded seams, when properly executed, are among the strongest seam systems available.

**Primary challenge:** Seam quality is highly dependent on installer skill and equipment calibration. Under- or over-welded seams are a leading cause of TPO failures.

**Best applications:** Climate-controlled buildings seeking energy efficiency, new construction, ENERGY STAR compliance projects.

PVC (Polyvinyl Chloride)

A premium single-ply thermoplastic membrane with excellent chemical resistance and the longest commercial track record among thermoplastic systems.

**Key specifications:**

• •Thickness: 50-mil, 60-mil, or 80-mil
• •Seam method: Hot-air heat welding
• •Color: White (standard), gray, tan
• •Lifespan: 20-30+ years

**Why it works in New England:** Similar energy benefits to TPO. Superior chemical resistance makes PVC the clear choice for restaurants or industrial facilities. Dimensional stability better than EPDM.

**Primary challenge:** Higher cost than EPDM or TPO. Older-generation PVC had plasticizer migration issues; modern formulations are greatly improved.

**Best applications:** Restaurants, food processing, chemical or grease exposure environments, premium specifications where maximum seam strength and chemical resistance are required.

Modified Bitumen Systems

Modified bitumen uses polymer-modified asphalt applied in multiple layers, similar in concept to traditional built-up roofing but with improved flexibility and performance.

APP-Modified Bitumen

Atactic polypropylene-modified bitumen, typically torch-applied. Produces a tough, durable multi-layer system.

SBS-Modified Bitumen

Styrene-butadiene-styrene-modified bitumen, more flexible than APP. Can be torch-applied, self-adhered, or cold-applied.

**Applications:** Smaller flat sections on residential properties (porch roofs, additions), re-roofing over existing modified bitumen, situations where contractor familiarity with the system is high.

**Limitation:** Torch application requires careful fire precautions and is prohibited in some jurisdictions without special permits. Shorter lifespan than single-ply membranes (15-20 years).

Built-Up Roofing (BUR)

Traditional built-up roofing uses alternating layers of roofing felt and hot-applied asphalt or cold adhesive, topped with aggregate (gravel) or cap sheet. Once the dominant commercial system, BUR has been largely displaced by single-ply membranes in new construction.

**Remaining applications:** Re-roofing or repair on existing BUR systems where matching the existing system is preferred.

Coatings and Recovery Systems

For aging but structurally sound flat roofs, coatings and recovery systems can extend service life without full replacement:

**Elastomeric coatings:** Applied over existing membranes to restore waterproofing and add UV protection. Cost-effective alternative to full replacement when the existing membrane is intact but aged.

**Re-cover systems:** New single-ply membrane installed over existing membrane (with proper recovery board to address moisture and flatness). Applicable when the existing membrane passes core testing.

Choosing the Right System

The right system depends on:

• •Budget and ownership timeline
• •Building use (chemical/grease exposure, climate control, foot traffic)
• •Existing roof condition and compatibility
• •Energy efficiency priorities
• •Contractor expertise available

Roofing Doctors has experience with all major commercial roofing systems and can recommend the right approach for Massachusetts and Rhode Island commercial properties.