Commercial Roofing Systems: The Complete Guide for Building Owners and Facility Managers

Commercial roofing decisions carry stakes that residential decisions do not. A failed commercial roof means interrupted business operations, damaged inventory, potential tenant disputes, and liability exposure — not just a home repair inconvenience. Building owners and facility managers who understand their roof system’s design, maintenance requirements, and failure modes make better decisions on every front: contractor selection, maintenance spending, insurance coverage, and capital planning.

This guide covers the full range of commercial roofing systems installed by our team at Lifetime Construction Builders’ commercial roofing division, with specific attention to the Arkansas and Michigan markets where building codes, climate demands, and available labor differ meaningfully. For residential and agricultural sloped metal roofing, see our metal roofing guide.

Types of Commercial Roofing Systems

Commercial roofing systems divide into two broad categories by application: membrane systems for flat and low-slope structures, and panel systems for sloped commercial and industrial buildings.

Membrane Systems (Flat and Low-Slope)

Single-ply membranes (TPO, EPDM, PVC), multi-ply systems (BUR, modified bitumen), and spray-applied systems cover flat and low-slope commercial structures. These systems rely on continuous membrane integrity rather than gravity drainage — the membrane is the waterproofing layer, and any penetration or seam failure immediately compromises the entire system at that location.

Panel Systems (Sloped Commercial)

Metal panel systems — R-panel, standing seam, and structural insulated panels — are appropriate for commercial buildings with pitches above approximately 1.5:12. Agricultural, light industrial, and commercial retail buildings are the primary applications. We install 26-gauge R-panel and 24-gauge standing seam commercial systems.

Single-Ply Membranes: TPO, EPDM, PVC

TPO (Thermoplastic Polyolefin)

TPO is currently the most commonly installed commercial roofing membrane in the United States, accounting for approximately 40% of new commercial flat roof installations. TPO membranes are heat-weldable thermoplastics — the seams between sheets are fused by hot air at temperatures around 1,000°F, creating a continuous watertight bond that is typically stronger than the parent membrane material.

Available thicknesses: 45 mil, 60 mil, and 80 mil. We specify 60-mil minimum for new commercial installations in both Arkansas and Michigan. 45-mil membranes are adequate for low-traffic roofs with controlled penetration counts, but the 15-mil thickness difference provides meaningful puncture resistance and seam integrity improvement for the modest cost premium. 80-mil is specified for high-traffic areas, mechanical equipment zones, and re-cover applications over existing single-ply systems.

Installation methods: Mechanically attached (fastened through membrane into decking or insulation with fastening plates), fully adhered (bonded to substrate with TPO adhesive), and ballasted (held in place by river rock or concrete pavers at 10 lbs/sq ft). Mechanically attached is the most common installation method in our markets — it tolerates more substrate imperfection than fully adhered, accommodates thermal movement without membrane stress, and does not require the additional structural capacity that ballasted systems need.

Reflectivity: White TPO achieves a solar reflectance index (SRI) of 80-90, making it one of the most energy-efficient commercial roofing options available. White TPO is ENERGY STAR qualified and qualifies for cool roof credits in both Arkansas and Michigan. In central Arkansas, where commercial cooling accounts for 40-60% of building energy use, white TPO can reduce HVAC loads by 15-30% compared to dark-surfaced built-up roofing systems.

EPDM (Ethylene Propylene Diene Monomer)

EPDM is a thermoset rubber membrane — it cannot be heat-welded and instead requires adhesive or tape seaming systems. EPDM has been commercially available since the 1960s and has the longest field performance record of any single-ply membrane. Fully adhered EPDM systems from the 1980s are still performing in many markets.

Available thicknesses: 45 mil and 60 mil. 60 mil is our standard specification. EPDM is inherently black (the base material is carbon-black stabilized); white EPDM is available but at a premium, and reflectivity remains lower than white TPO.

Installation methods: Fully adhered, mechanically attached, or ballasted. EPDM’s flexibility at extreme temperatures makes it particularly appropriate for Michigan installations where winter temperatures of -20°F are possible — EPDM maintains flexibility at temperatures that would stress TPO seams. For Michigan commercial projects with frequent freeze-thaw cycling, EPDM is our preferred membrane over TPO.

Performance in Michigan: EPDM’s low-temperature flexibility advantage is well-documented. At -40°F, EPDM remains flexible; some TPO formulations begin to lose flexibility below -20°F. For cold-storage facilities, northern Michigan industrial buildings, and any structure where winter temperature extremes are a primary concern, EPDM’s performance advantage is meaningful.

PVC (Polyvinyl Chloride)

PVC membranes are heat-weldable (like TPO) and have excellent chemical resistance properties that make them the correct specification for commercial kitchens, restaurants, chemical processing facilities, and any application where rooftop grease, cooking exhaust, or chemical exposure is present. EPDM and TPO are degraded by grease and many chemicals; PVC is resistant.

Available thicknesses: 50 mil and 60 mil. PVC is typically more expensive than TPO by $0.50-$1.50/sq ft installed. The premium is justified only where chemical resistance is needed — for standard commercial office, retail, and warehouse applications, TPO or EPDM is the more economical choice.

SBS Modified Bitumen

Modified bitumen is a two-ply membrane system using asphalt modified with styrene-butadiene-styrene (SBS) rubber polymer. SBS-modified asphalt remains flexible at low temperatures — the rubber modification is the same technology that makes polymer-modified asphalt shingles outperform standard asphalt in cold climates. Modified bitumen systems are applied in two layers (base sheet and cap sheet), with the cap sheet typically torch-applied or cold-adhesive applied.

SBS modified bitumen is more common in Michigan commercial applications than in Arkansas, primarily because its cold-weather flexibility advantage is a genuine operational benefit in the western Michigan market. It is also the appropriate specification for re-cover applications over existing built-up roofing where complete tear-off is disruptive or cost-prohibitive.

BUR (Built-Up Roofing)

Built-up roofing (BUR) is the traditional flat roof system — alternating layers of reinforcing felt and asphalt or coal tar pitch, surfaced with gravel or mineral cap sheet. BUR systems installed in the 1970s and 1980s remain on many commercial buildings in both our markets. Modern BUR installation has largely been displaced by single-ply membranes in new construction, but BUR remains appropriate for specific applications: historic preservation where the existing system is being maintained, applications requiring maximum ballast mass for wind uplift resistance, and situations where gravel surfacing provides specific foot-traffic protection benefits.

Spray Polyurethane Foam (SPF)

Spray foam is applied in liquid form and self-adheres to the existing roof substrate, expanding to form a closed-cell insulated waterproof layer. SPF provides both insulation and waterproofing in a single application, which is its primary advantage on buildings where adding thermal insulation thickness is the primary goal. SPF requires recoating every 10-15 years with an elastomeric coating to protect the foam from UV degradation. Without the recoat, foam degrades rapidly.

Flat Roof vs. Low-Slope Design

The term “flat roof” is technically inaccurate — all properly designed flat roofs have minimum drainage slope. The distinction in roofing terminology:

• Flat roof: 0:12 to 0.25:12 slope (essentially horizontal). Drainage is provided entirely by internal drains or secondary drainage systems. These roofs require the most sophisticated drainage design and the most robust waterproofing systems.
• Low-slope roof: 0.25:12 to 2:12. Minimum slope drains toward either internal drains or perimeter gutters. Single-ply membranes are appropriate across this slope range.
• Steep-slope commercial: 2:12 and above. Metal panels, modified bitumen with mineral cap sheet, or conventional shingle systems are appropriate at this pitch.

Drainage design on commercial flat and low-slope roofs is as important as membrane selection. Ponding water — water that stands more than 48 hours after rainfall — is a universal commercial roofing warranty exclusion. It concentrates UV exposure at the water-air interface, accelerates seam stress at the edges of ponded areas, and increases structural load beyond design intent if water accumulates from clogged drains. Drainage slope must be designed into the insulation system when the structural deck is flat.

Material Comparison Matrix

Cost Analysis by System Type

Commercial roofing costs are project-specific to a degree that residential roofing is not. The variables affecting commercial pricing are more numerous and carry greater cost weight:

Factors That Drive Commercial Roofing Costs

• Penetration count: Every HVAC unit, pipe, drain, curb, and skylight is a penetration requiring individual flashing work. A commercial building with 40 rooftop HVAC units can have 200+ penetrations requiring detailing. Penetration work drives labor costs far more than membrane material costs.
• Existing conditions: Tear-off costs, decking condition, existing insulation requirements, and code-mandated upgrades all affect total project cost. Commercial buildings often have layered re-cover systems from previous projects — discovering three layers of existing roofing during tear-off increases disposal costs significantly.
• Access and logistics: Multi-story buildings require cranes or material lifts. Occupied buildings require work scheduling that minimizes tenant disruption. Urban sites may require lane closures or special permits for equipment access.
• Insulation thickness: Commercial building energy codes (Arkansas Energy Code and Michigan Energy Code) specify minimum insulation R-values that have increased significantly in recent code cycles. Adding code-required insulation to a re-roofing project is a substantial cost item — R-25 to R-30 in continuous polyisocyanurate insulation above the deck adds $1.50-$3.00/sq ft to the base membrane cost.

Installed Cost Ranges by System (Commercial, per sq ft)

• 60-mil TPO mechanically attached: $5.50-$9.00/sq ft
• 60-mil TPO fully adhered: $7.00-$11.00/sq ft
• 60-mil EPDM mechanically attached: $5.00-$8.50/sq ft
• 60-mil EPDM fully adhered: $6.50-$10.00/sq ft
• 60-mil PVC mechanically attached: $6.50-$10.50/sq ft
• SBS modified bitumen (2-ply): $5.00-$8.00/sq ft
• BUR (4-ply, gravel-surfaced): $7.00-$12.00/sq ft

These ranges do not include tear-off ($0.75-$2.50/sq ft), deck repair, insulation upgrades, or mechanical unit curb flashing — all of which add to total project costs. A complete commercial re-roofing project budget should include a 15-20% contingency for conditions not visible during initial assessment.

Installation Timelines

Commercial roofing timelines depend on building area, system complexity, and weather. General planning parameters:

• Small commercial (under 10,000 sq ft): 3-7 working days for standard single-ply mechanically attached system
• Medium commercial (10,000-50,000 sq ft): 1-3 weeks depending on crew size and penetration complexity
• Large commercial (50,000+ sq ft): Phase planning required — typically 4-12 weeks with sections completed and secured before moving to adjacent areas

Arkansas commercial work is constrained primarily by heat — working on a black membrane surface in August in central Arkansas creates heat illness risk above 95°F ambient temperature. Early morning starts (6 AM) and weather monitoring are standard practice for summer commercial projects in the Bryant/Little Rock market.

Michigan commercial work is constrained by temperature and moisture. TPO heat welding requires minimum ambient temperature of approximately 35-40°F for reliable seam quality. Cold-adhesive systems can be installed at lower temperatures. November through March in western Michigan frequently requires weather monitoring and heated work tents for quality-controlled installation of temperature-sensitive systems.

Maintenance Programs

Commercial roofing maintenance is not optional — it is a warranty requirement and a financial obligation to the asset. Most commercial roofing warranties require documented semi-annual inspections as a condition of warranty validity. We offer structured maintenance programs for our commercial customers in both Arkansas and Michigan:

Basic Annual Program

• Two inspections per year (spring and fall)
• Written inspection report with photographs documenting all findings
• Minor maintenance: re-sealing penetrations, repairing membrane surface blisters, clearing drains
• Drain cleaning (typically 4-6 drains per building)

Comprehensive Program

• All basic program items
• Infrared moisture scan (every 3-5 years) to identify water-saturated insulation before membrane failure spreads
• Seam probing and repair
• Curb flashing inspection and re-seal at all HVAC units
• Detailed condition report with repair recommendations and capital planning guidance

Value of Maintenance Documentation

Documented inspection and maintenance records provide three concrete benefits: warranty compliance (maintaining manufacturer warranty coverage), insurance claim documentation (demonstrating regular maintenance when filing a storm damage claim), and capital planning evidence (providing the data needed to justify budget requests for major roof projects to ownership and boards).

Energy Efficiency and Reflectivity

Commercial roofing’s energy impact is proportionally larger than residential because flat commercial buildings have a higher ratio of roof area to conditioned space volume. The roof surface is the primary solar heat gain pathway for single-story retail, warehouse, and office buildings.

Cool Roof Standards

ENERGY STAR Cool Roof certification requires minimum initial solar reflectance of 0.65 and minimum three-year aged solar reflectance of 0.50. White TPO meets these standards. White EPDM meets initial reflectance but ages to lower reflectance than TPO. Granulated modified bitumen and standard BUR do not meet cool roof standards — their dark surfaces absorb 80-90% of solar radiation.

Arkansas Energy Impact

Central Arkansas’s cooling-dominated climate makes cool roof specification the correct default for commercial buildings. The Arkansas Energy Code (based on IECC 2018) requires cool roof compliance for most low-slope commercial applications. White TPO, beyond code compliance, delivers documented cooling energy reductions of 20-40% compared to dark membrane systems in hot-summer climates. For a 20,000 sq ft warehouse paying $2,000/month in summer cooling costs, a 25% reduction represents $500/month or $6,000 annually — significant enough to justify the modest premium of white over black membrane.

Michigan Energy Impact

Western Michigan’s heating-dominated climate creates less clear-cut cool roof economics. The winter heating penalty of a white reflective roof (losing potential solar heat gain) partially offsets summer cooling savings. For Michigan commercial buildings with significant heating loads, EPDM’s darker surface has a slight energy advantage in the heating season. However, Michigan energy code compliance still requires cool roof metrics for most commercial building types — verify project-specific compliance requirements with the local building department.

Warranty Types

Commercial roofing warranties are structurally more complex than residential warranties. Understanding the distinction between warranty types is essential to knowing what protection you actually have.

Manufacturer Material Warranty (No-Dollar-Limit NDL)

The highest-value warranty in commercial roofing is the manufacturer No-Dollar-Limit (NDL) warranty. An NDL warranty means the manufacturer will pay all costs — materials and labor — to repair any warranty-covered failure, with no cap on the total dollar amount. NDL warranties typically require:

• Installation by a manufacturer-certified contractor
• Pre-installation approval of the project design
• Post-installation inspection and closeout documentation
• Documented semi-annual inspections throughout the warranty period

Standard NDL warranty periods run 10, 15, or 20 years. Extended warranty products (25 and 30 years) are available at premium pricing. We are certified by TPO, EPDM, and PVC membrane manufacturers to issue NDL warranties on qualifying installations.

Material-Only Warranty

Material-only warranties cover membrane replacement but not labor. For a 20-year-old commercial building with a failed membrane, the labor cost to tear off and reinstall is typically 60-70% of the total replacement cost. A material-only warranty provides limited protection against the full replacement cost exposure. Avoid material-only warranties for commercial installations of any significant size.

Contractor Workmanship Warranty

Separate from the manufacturer warranty, a contractor workmanship warranty covers installation defects for a period after completion. Our standard commercial workmanship warranty is 5 years. This covers failures resulting from installation errors that fall outside the manufacturer’s warranty scope. Given that labor defects are the primary failure mode in commercial membrane roofing, a substantial contractor warranty is as important as the manufacturer’s warranty.

Inspection Standards

Commercial roof inspections follow established protocols. An adequate commercial inspection includes these elements:

Exterior Inspection

• Membrane surface condition: blisters, fishmouths, open seams, surface erosion, punctures
• Penetration flashing condition: all HVAC curbs, pipe flashings, drain flanges, wall terminations
• Parapet and coping condition
• Drain and gutter condition: debris accumulation, scupper blockage, gutter alignment
• Adjacent wall and penetration conditions that could affect water infiltration

Interior / Attic Inspection

• Decking condition: visible from below for deflection, staining, or rot
• Insulation moisture: wet insulation is cold to the touch and often visible as dark staining from below
• Condensation evidence at roof-wall intersections

Infrared Moisture Scanning

Infrared thermographic scanning identifies moisture-saturated insulation beneath the membrane by detecting temperature differences between wet and dry insulation. Wet insulation holds heat after sundown (thermal lag) that dry insulation does not, and infrared cameras detect this differential. Infrared scanning identifies insulation that is wet beneath an apparently intact membrane — the most cost-effective tool for targeted repairs before full membrane failure.

Building Codes: Arkansas vs. Michigan

Arkansas Commercial Building Code

Arkansas has adopted the International Building Code (IBC) 2018 and the International Energy Conservation Code (IECC) 2018 as the state baseline, with local jurisdictions permitted to adopt local amendments. Saline County and City of Bryant follow the state baseline with limited local amendments. Key provisions affecting commercial roofing:

• Minimum insulation: Climate Zone 3 (central Arkansas) requires R-20 minimum for low-slope roof assemblies in commercial new construction. Re-roofing projects may have limited insulation upgrade requirements depending on scope — full tear-off typically requires bringing the assembly to current code.
• Wind design: Arkansas commercial buildings in Saline County are typically designed for 115-120 mph basic wind speed (ASCE 7-22 ultimate design wind speed). Roof membrane systems must demonstrate wind uplift resistance meeting FM 1-90 or higher depending on building risk category.
• Contractor licensing: Commercial roofing projects in Arkansas require a licensed commercial contractor. Arkansas Contractors Licensing Board issues separate residential and commercial contractor licenses.

Michigan Commercial Building Code

Michigan has adopted the Michigan Building Code (MBC) based on IBC 2021 with Michigan-specific amendments. Key provisions:

• Minimum insulation: Climate Zone 5 (western Michigan, including Allegan County) requires R-30 minimum for low-slope commercial roof assemblies in new construction. This is 50% more insulation than required in Arkansas — a significant project cost difference.
• Wind design: Western Michigan coastal areas (Lake Michigan shoreline) are designated as special wind speed zones. Allegan County coastal areas may require enhanced FM 1-120 or FM 1-150 wind uplift ratings depending on building exposure category.
• Snow load: Michigan structural designs must account for ground snow loads that exceed national baseline values in lake effect zones. Commercial structures in Allegan County are typically designed for 25-30 psf ground snow load — verify with the structural engineer of record.
• Ice barrier requirements: Michigan building code requires ice barrier membrane at eaves for all roof assemblies — more stringent requirements than Arkansas.

Insurance Considerations

Commercial Property Insurance

Commercial roofing insurance claims differ from residential in several important ways. Commercial policies are typically scheduled property policies with specific coverage limits by building, rather than homeowners policies with open-form coverage. The commercial property insurer’s adjusting process is more technical and documentation-intensive than residential.

For commercial claims, maintain documentation of your roof’s installation date, membrane type, warranty status, and all inspection and maintenance records. A documented maintenance history is the single most effective tool for countering an insurer’s assertion that damage resulted from deferred maintenance rather than a covered storm event.

Business Interruption Coverage

For commercial buildings with occupied tenants or active business operations, roof damage that forces temporary closure generates business interruption losses beyond the physical damage. Most commercial property policies include business interruption coverage, but limits and waiting periods vary. Verify your business interruption limits relative to your actual monthly revenue before a claim scenario — inadequate limits are frequently discovered only after the fact.

Roof Age and Insurability

Commercial insurers in both Arkansas and Michigan increasingly inspect roofs before issuing or renewing commercial property policies. A commercial roof more than 15-20 years old, or showing visible deterioration on aerial imagery, may trigger a required inspection or a policy condition requiring repair or replacement to maintain coverage. Proactive roof maintenance documentation reduces this risk significantly.

Repair, Coat, or Replace Decision

The three options for a deteriorating commercial roof have different economics and risk profiles:

Repair

Appropriate when: The membrane is less than 15 years old, damage is localized to specific areas, insulation moisture content (from infrared scanning) is less than 20% by area, and no systemic seam failure is present. Targeted repairs can extend membrane life by 5-10 years when the base system has remaining integrity.

Coating

Roof coatings (elastomeric acrylic, silicone, or SPF recoat) restore reflectivity, seal minor surface issues, and can extend membrane life by 10-15 years when the base membrane is still structurally intact but showing surface degradation. Coating is not appropriate when the insulation is wet — coating over wet insulation traps moisture, accelerates insulation degradation, and creates conditions for membrane failure. Infrared moisture scanning before coating is essential to verify coating is appropriate.

Silicone coating has become the preferred commercial coating system in recent years: it is UV-stable (does not chalk or degrade under UV like acrylic), performs on wet surfaces and in standing water, and adheres to virtually all membrane types including aged TPO and EPDM. Application rate: typically 1.5-2.5 gallons per 100 square feet. Installed cost: $2.00-$4.00/sq ft for full coating system.

Full Replacement

Appropriate when: Infrared scanning identifies wet insulation covering 25% or more of total roof area, multiple seam failures are present, the membrane has reached its service life (20+ years for standard TPO/EPDM, 30+ for EPDM on well-maintained systems), or energy code upgrades to insulation R-value are required. Full replacement resets the warranty clock and allows insulation upgrade to current code.

Multi-Tenant Considerations

Multi-tenant commercial buildings present specific roofing challenges that single-tenant properties do not:

Lease Clause Review

Commercial leases typically assign roof maintenance responsibility to the landlord but may allocate specific costs (such as HVAC unit flashing repairs or penetration sealing for tenant equipment) to tenants. Before beginning any commercial roofing project on a multi-tenant building, review all active leases for provisions affecting roofing work — tenant notification requirements, work hour restrictions, and maintenance cost allocation language can all affect project planning.

Work Scheduling

Occupied multi-tenant buildings require phased work schedules that minimize disruption to tenants’ business operations. Tear-off and installation over occupied spaces must maintain continuous waterproof protection — partial completion without weather-tight closure creates liability exposure and potential tenant claims for water damage. We schedule commercial projects in phases that allow each section to be completely installed and weather-tight before moving to adjacent areas.

Common Area vs. Tenant Area Responsibility

In multi-tenant commercial buildings, roofing above tenant spaces is typically a common area landlord responsibility, while rooftop HVAC equipment installed by or for specific tenants may be a tenant capital item. The mechanical units’ roof penetrations and associated flashings are the landlord’s responsibility regardless of who owns the equipment. Clarify cost responsibility in writing before work begins.

Frequently Asked Questions

How long does a commercial roof last?

With proper maintenance, 60-mil TPO and EPDM systems regularly achieve 25-30 year service lives. BUR systems in good condition can last 30-40 years. Metal panel systems (R-panel and standing seam) last 30-50 years. The primary variable is maintenance — neglected commercial roofs fail in 10-15 years regardless of the membrane quality; well-maintained systems reach their full potential service life. Our maintenance program documentation supports both warranty compliance and capital planning for building owners.

What is the difference between a commercial and residential roofing contractor?

Commercial roofing requires different licensing, equipment, skills, and system knowledge than residential roofing. In Arkansas, commercial and residential contractor licenses are separate — verify your contractor holds the correct license classification for your project type. Commercial membrane installation requires heat welding equipment (for TPO and PVC), infrared testing equipment, and experience with commercial drainage design that most residential contractors do not have. We hold active commercial contractor licenses in both Arkansas (RR0540591024) and Michigan (252400088).

Do I need a permit for commercial roof replacement?

Yes, in virtually all jurisdictions. Commercial roof replacement is a permitted work scope in Arkansas and Michigan. Permit requirements include code-compliant insulation R-values, wind uplift resistance documentation, and in some jurisdictions, energy compliance verification. We manage permit applications as part of our commercial project process — the building owner should not be chasing permits independently.

What causes ponding water on a flat commercial roof?

Three causes: (1) Clogged internal drains — the most common and most preventable cause; (2) Structural deflection — roof decking that has deflected over time under sustained load, creating low points that collect water; (3) Inadequate original drainage slope design — re-roofing with tapered insulation is the corrective measure for structural or design-origin ponding. Clogged drains are a maintenance issue addressed by drain cleaning (quarterly or semi-annually depending on debris load). Structural deflection and design-origin ponding require engineering evaluation.

How do I know when my commercial roof needs replacement vs. repair?

Infrared moisture scanning provides the most objective data. When wet insulation covers 25% or more of the total roof area, replacement typically costs less than comprehensive repair over the following 5-7 years because wet insulation continues to migrate and will eventually compromise the entire system. We recommend infrared scanning every 5 years on commercial roofs over 10 years old as standard capital planning practice. The scan costs $0.05-$0.10/sq ft and provides data worth far more than its cost in avoided deferred maintenance surprises.

What is a TPO “fish mouth” and why does it matter?

A fish mouth is a small wrinkle or pucker in a TPO seam where the membrane did not lay flat before welding — the seam welds over the wrinkle, leaving a gap beneath the welded area at the seam edge. Fish mouths are a common installation quality indicator — they indicate that the installer did not properly prepare membrane alignment before welding. Fish mouths are a direct water infiltration point and must be cut open, flattened, and re-welded with a patch. Their presence on a new installation is a quality indicator worth noting during acceptance inspection.

Can I install rooftop solar on my commercial building?

Yes, and commercial TPO is one of the best substrates for solar installation. Ballasted solar racking systems sit on top of the membrane with paver or block ballast — no penetrations. Penetration-based racking requires core drilling through the membrane with sealed penetration flashings. For single-ply commercial roofs, ballasted systems are preferred to minimize penetration count. Verify that the added ballast load (typically 3-5 lbs/sq ft for ballasted commercial solar) is within the structural capacity of your roof assembly before installation.