RCAT Blog: Low & Steep Slope Roofing What Contractors Need to Know

Insights from Mark Graham, NRCA Vice President of Technical Services

Roofing success depends on understanding more than just the products you install. 

Every roofing system comes with its own technical challenges, code requirements, and hidden liabilities.

In this session recap, Mark Graham, Vice President of Technical Services for the National Roofing Contractors Association (NRCA), delivers practical lessons that contractors can apply immediately in the field. 

From safety hazards to specification traps, Graham’s expertise helps roofing professionals make better technical and business decisions.

This article summarizes the most relevant takeaways from his presentation.
 

Watch the full session here: https://www.youtube.com/watch?v=yqMpDB7WcVM 

Understanding Market and Material Trends

Before diving into the technical side, Graham outlined key industry trends contractors should keep an eye on.

• Shingle and low-slope activity continues to hold steady, reflecting strong reroof demand rather than storm-driven spikes.
• Material costs have risen dramatically since 2020, particularly for petroleum-based products and roofing asphalts. Contractors should review pricing structures to ensure costs and revenues stay aligned.
• Backlogs remain common, with many contractors reporting multiple months of work already on the books. This underscores the need for disciplined project selection and margin protection.
   

Rooftop Safety: Hidden Hazards from RF Radiation

One of the most overlooked safety issues today is radio frequency (RF) radiation from rooftop cell antennas. 

With the expansion of 5G networks, antennas are now smaller, stronger, and more widespread—even appearing on two-story commercial and residential structures.

What contractors need to know:

• RF exposure is regulated by the FCC, not OSHA, meaning typical safety inspectors may overlook it.
• Always look for signage near hatches, parapets, or equipment penthouses. Warning colors (blue, yellow, red) indicate exposure zones.
   
• Contact the building owner or leasing company for site-specific RF safety data before starting work.
   
• When exposure is unavoidable, request that antennas be powered down during the project.
   
• In Canada, personal RF monitors are now recommended for roof workers; similar precautions may become best practice in the U.S.
   

RF symptoms can mimic heat stress—headache, fatigue, dizziness—so jobsite awareness and coordination are key to keeping crews safe.

Underlayment Codes: The Details That Matter

The International Building Code (IBC) section 1507.1 specifies underlayment standards for steep-slope roofs, and regional wind speed maps determine which column of the code applies.

For Texas contractors:

• Most inland regions require compliance with 120–130 mph design wind speeds, while coastal zones exceed 140 mph.
   
• This difference dictates whether #15 or #30 felt is the minimum acceptable underlayment.
   
• Higher wind zones require wider laps, closer fasteners, and taped joints to prevent blow-offs.
   
• Synthetic underlayments are officially recognized in the 2024 code update, reducing confusion during inspections.
   

Although these standards seem minor, overlooking them can cause inspection delays or code violations—especially in coastal municipalities.

Nailbase Insulation: Handle with Caution

Nailbase insulation continues to create field headaches, especially when fire-retardant-treated (FRT) or pressure-treated plywood is laminated. Trapped moisture in packaging leads to warping, cupping, and adhesion failure.

Best practice:

• Avoid single-layer nailbase applications when possible. Use two layers—ISO first, then a thinner nailbase—to offset joints and improve thermal continuity.
   
• Be cautious of FRT plywood nailbase systems. If a specification requires it, walk away rather than absorb the liability.
   
• Proper sequencing and moisture control during storage are essential to avoid deformation and warranty disputes.
   

High-Temp Underlayments and Metal Roofs

Many “high-temp” peel-and-stick products fail under metal roofing systems in hot climates. Graham emphasized that “high-temp” is a marketing term, not an engineering standard.

Field experience suggests:

• Temperatures under light-colored metal panels can exceed 120–130°F, easily softening asphalt adhesives.
   
• For these applications, separate the membrane from the deck with a mechanically fastened base sheet before applying the peel-and-stick.
   
• Manufacturers use different formulations, so performance varies widely—always check the product’s data sheet for temperature limits.
   

ISO Insulation: The R-Value Problem

ISO insulation is sold by LTTR (Long-Term Thermal Resistance), but testing cycles are delayed—values reported today may reflect product made six months ago.

Graham’s advice:

• Request current conformance documentation from your distributor before shipment.
   
• Avoid making R-value promises in contracts. Instead, specify thicknesses and performance by assembly type.
   
• Selling “R-30 roofs” invites liability if the product later fails to meet its published value.
   

Fasteners and FM Approvals

Imported fasteners marketed as “FM approved” have caused jobsite failures and liability issues. Bending shanks and shearing heads are common complaints.

Recommendations:

• Always purchase fasteners through membrane manufacturers or approved distributors.

• Confirm current FM listings directly in RoofNav before installation.
   
• Document your submittals—approvals can change, and outdated data is not defensible in warranty claims.
   

Field Uplift Testing: Proceed Carefully

Roof uplift testing in the field often fails to match Factory Mutual’s laboratory results. Independent testing has shown wide variability, even under identical conditions.

Key point:
 

Do not rely on field uplift tests as your final proof of performance. Instead, focus on installation accuracy, fastener spacing, and edge detailing. Misapplied testing criteria can generate false failures and unnecessary legal exposure.

Vapor Retarders and Concrete Decks

NRCA testing confirms that properly applied vapor retarders adhere strongly to cured concrete decks, even under thermal differentials that simulate vapor drive.

Takeaways:

• Always include a vapor retarder over new concrete decks.
   
• Prime when required, roll or broom-in per manufacturer instructions.
   
• Cover promptly with the roof system to prevent blistering.
   
• Temporary exposure is acceptable, but any blisters that form should be cut and patched before final installation.
   

Warranty Wind Speeds vs. Design Requirements

One of the most misunderstood gaps in roofing contracts is the mismatch between warranty wind exclusions and code design wind speeds.

For example, warranties might exclude winds above 60 mph—even though code design in much of Texas exceeds 120 mph. Manufacturers can use this as a reason to deny claims unrelated to actual wind damage.

Contractor checklist:

• Align your contractor warranty with the manufacturer’s exclusion limits.
   
• Keep design calculations and code compliance documentation on file.
   
• Educate building owners upfront to avoid unrealistic expectations.
   

Deck Loading and Material Storage

Material staging remains one of the most frequent—and preventable—causes of deck damage. A single pallet of shingles can weigh more than 4,000 pounds, creating excessive point loads on bar joists or metal deck.

Before loading a roof:

• Confirm joist orientation and spread materials across multiple bays.
   
• Keep heavy rolls and adhesives perpendicular to joists.
   
• Use dunnage to distribute concentrated loads evenly.
   
• Coordinate delivery schedules to minimize on-deck storage.
   

The Bottom Line

Mark Graham’s guidance reinforces one message: technical awareness prevents business problems. From safety to specification to warranties, the best contractors think beyond installation.

Every roof is a system shaped by codes, materials, and human choices. Use these lessons to tighten your practices, protect your crews, and strengthen your reputation.

Credit

This summary is based on a technical session by Mark Graham, Vice President of Technical Services, NRCA.

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Watch the full presentation: https://www.youtube.com/watch?v=yqMpDB7WcVM 

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