Project at a Glance
Project Ref GTR7171NewMarket · Verified 11/2025- Building Type
- Occupied retail center
- Location
- 7171 New Market Ct, Manassas, VA
- Roof Area
- 25,857 SF
- Existing System
- Duro-Last over polyiso on metal deck
- Replacement System
- Elevate UltraPly 60 mil TPO
- Insulation
- R-20 PolyISO
- Attachment
- Mechanically fastened
- Drainage Correction
- 6 major ponding slopes corrected
- Deck Repair
- 240 SF W metal deck replaced
- Drains
- 8 rebuilt, including pipe connections
- HVAC Curbs
- 11 rebuilt
- Penetrations
- 72 pipe and vent
- Warranty Issued
- 20-year Elevate Red Shield NDL
- Start Date
- 12/2023
- Completion Date
- 01/2024
- Duration
- 21 working days
- Building Occupancy
- Fully tenanted throughout
- Recordable Incidents
- 0
Executive Summary
What This Project Involved
The existing roof at this Manassas retail center was a 25,857-square-foot Duro-Last assembly installed over polyisocyanurate insulation board on a metal roof deck. The membrane had reached the end of its service life, with widespread shrinkage, split seams, and extensive prior patching associated with a long leak history. Across approximately 20% of the roof the membrane had lost its protective upper coating entirely, leaving only the middle scrim mesh exposed, so water passed straight through the remaining reinforcement rather than being shed. Six major low areas held standing water well past 48 hours because the original assembly had never been sloped correctly to the drains, and the drain assemblies themselves had deteriorated.
GoTech completely removed the existing membrane and insulation down to the metal deck. Tear-off exposed 240 square feet of W-type metal decking that had rusted completely through beneath the long-leaking membrane, to the point that daylight was visible through the corrosion holes, and that section was cut out and replaced with new decking. The remaining deck showed only light surface rust and was sound, so it was wire brushed with a deck preparation tool and coated with red oxide rust-inhibitive primer to arrest further oxidation before the new system went down. The roofing system was then rebuilt with R-20 polyisocyanurate insulation and a mechanically fastened Elevate UltraPly 60-mil TPO membrane. Tapered insulation and large water-shedding crickets were incorporated into the new insulation layer to correct all six major ponding slopes, so the drainage defect was designed out of the roof rather than carried forward into the new system.
All eight roof drains were rebuilt along with their drain pipe connections, 11 HVAC curbs were reconstructed and reflashed, and 72 pipe and vent penetrations received new pre-molded Elevate flashing. Work was staged so no opened roof section was left exposed overnight and the retail center remained fully tenanted throughout. The completed roof received a 20-year Elevate Red Shield No Dollar Limit warranty, and the project was finished in 21 working days with zero recordable safety incidents.
Starting Point
Existing Conditions
The existing Duro-Last roof was exhibiting system-wide deterioration rather than a single isolated leak condition. Deficiencies included loss of the membrane's protective upper coating over roughly a fifth of the roof, membrane shrinkage and seam splitting, failed flashing at rooftop equipment, deteriorated drain assemblies, rusted-through metal decking beneath long-standing leaks, and persistent ponding across six major low areas created by inadequate slope. The conditions were documented by component so the extent of deterioration could be compared directly with the diagnostic testing that followed.
| Location | Observed condition | Extent | Leak history |
|---|---|---|---|
| Membrane field | Widespread Duro-Last shrinkage, seam splitting, and extensive prior patching | 25,857 SF | Widespread reported leak history |
| Membrane coating loss | Protective upper coating weathered away, leaving only the middle scrim mesh so water passed directly through the membrane | Approx. 20% of roof area | Active leakage through exposed scrim |
| Roof assembly | Duro-Last membrane over polyisocyanurate insulation board on a metal roof deck | 25,857 SF | Associated with active leak conditions |
| Metal roof deck | W-type metal deck rusted completely through beneath long-term leakage, with daylight visible through the corrosion holes; remaining deck lightly surface rusted | 240 SF failed, balance of deck sound | Long-term leakage directly above tenant space |
| HVAC curbs | Failed curb flashing and corroded counterflashing | 11 curbs | Reported at multiple curb locations |
| Drainage | Ponding held well past 48 hours away from the drains due to inadequate slope | 6 major ponding areas | — |
| Drain assemblies | Deteriorated drain bodies and drain pipe connections | 8 drains | Leakage observed at drain connections |
| Penetrations | Aged and failing pipe and vent penetration flashing | 72 penetrations | Reported at multiple penetrations |
How We Know
Investigation & Diagnostics
The investigation focused on identifying the construction of the existing roof assembly, documenting active failure points, measuring retained moisture within the existing system, and separating membrane failure from drainage-design problems. Using multiple methods reduced reliance on any single test and provided the basis for determining whether repair, restoration, recover, or full replacement was appropriate.
| Method | Instrument / reference | Finding |
|---|---|---|
| Core sampling | Full-depth cores cut and patched the same day | Confirmed the assembly in sequence: metal roof deck, polyisocyanurate insulation board, and Duro-Last membrane |
| Capacitance moisture survey | Tramex non-destructive moisture meter | Non-destructive moisture readings were taken across the roof area to map retained moisture within the existing assembly and confirm the roof was not a candidate for recover or localized repair |
| Visual condition survey | Walk-over survey, NRCA inspection practice | Documented widespread Duro-Last shrinkage and seam splitting, loss of the protective upper coating across approximately 20% of the roof leaving only exposed scrim mesh, large seam failures, widespread prior patching, and multiple failed repairs associated with leak history |
| Deck inspection at tear-off | Direct examination of the exposed metal deck | 240 SF of W-type metal deck found rusted through with daylight visible from below and scheduled for replacement; the remaining deck was lightly surface rusted but structurally sound and suitable for wire brushing and rust-inhibitive priming |
| Drainage survey | Post-rainfall observation | Six major ponding areas identified for correction where inadequate slope held water away from the drains |
| Drain assessment | Inspection of drain bodies and pipe connections | Eight drains and their drain pipe connections were deteriorated and required rebuilding |
| Penetration survey | Component count and flashing condition review | 72 pipe and vent penetrations and 11 HVAC curbs required new flashing as part of the replacement |
Decision Record
Options Evaluated
Repair, restoration, recover, and complete replacement were evaluated against the documented membrane condition, the drainage deficiencies, remaining service life, occupant disruption, and availability of a long-term manufacturer warranty. The extent of seam failure, the loss of the membrane's protective coating over roughly 20% of the roof, and the six major ponding areas were primary factors, because installing a coating or recover system would have left the underlying slope defects, the deteriorated drains, and the corroding deck uncorrected and concealed.
| Option | Est. added service life | Tear-off | Disruption to occupants | Warranty available | Outcome |
|---|---|---|---|---|---|
| Continued repair | 1–3 years | None | Recurring above occupied tenant space | Workmanship only | Not selected |
| Coating restoration | Not viable | n/a | n/a | Not available at this seam condition | Not selected |
| Single-ply recover | 10–15 years | None, leaves slope defects in place | Moderate | Would not correct ponding or drains | Not selected |
| Full tear-off and TPO replacement | 20–25 years | Full, phased daily | Managed, no interior exposure | 20-year Red Shield NDL | Selected |
A membrane-only solution would have left the root causes in place: complete tear-off was the only approach that exposed the rusted-through deck for replacement and allowed the six major ponding slopes to be corrected and all eight drains and drain pipe connections to be rebuilt as part of a warranted assembly.
What Was Installed
Specified System
The replacement roof was designed as a complete system rather than a membrane-only installation. After removal of the existing Duro-Last and insulation to the metal deck, deteriorated decking was replaced and the remaining deck was prepared and primed, the thermal assembly was rebuilt with R-20 polyisocyanurate insulation, and tapered insulation and crickets were incorporated to correct six major ponding areas. Eight drain assemblies and their drain pipe connections were rebuilt, and 11 HVAC curbs and 72 pipe and vent penetrations were reflashed so the field membrane and roof interfaces functioned as one warranted assembly.
| Component | Installed work | Purpose / result |
|---|---|---|
| Tear-off | Existing Duro-Last membrane and polyisocyanurate insulation removed to the metal deck | Exposed the deck for inspection and removed the failed membrane and insulation across 25,857 SF |
| Deck replacement | 240 SF of rusted-through W-type metal decking cut out and replaced with new deck | Restored a sound structural substrate where long-term leakage had corroded the deck through |
| Deck preparation | Remaining lightly rusted deck wire brushed with a deck preparation tool and coated with red oxide rust-inhibitive primer | Inhibited further oxidation of the sound deck before the new assembly was installed |
| Insulation | R-20 polyisocyanurate insulation | Rebuilt the thermal layer over the metal deck |
| Tapered system | Tapered polyisocyanurate insulation and large water-shedding crickets | 6 major ponding slopes corrected to establish positive drainage |
| Membrane | Mechanically fastened Elevate UltraPly 60-mil TPO | New reflective single-ply replacement system |
| Drain assemblies | 8 drains and their drain pipe connections rebuilt | Integrated the drainage outlets into the new roof assembly and restored flow |
| HVAC curbs | 11 HVAC curbs rebuilt and reflashed | Reconstructed vulnerable transition points as part of the new warranted roof |
| Penetrations | 72 pipe and vent penetrations flashed with new pre-molded Elevate covers | Sealed every penetration to manufacturer detail requirements |
| Warranty | 20-year Elevate Red Shield No Dollar Limit warranty | Manufacturer-backed long-term coverage for the replacement system |
How It Was Delivered
Execution
The project was completed over 21 working days during December 2023 and January 2024.-
Scope development
GoTech documented the membrane failures, existing roof construction, drainage deficiencies, and leak-related conditions so the replacement scope, slope correction, and drain reconstruction could be defined before work began.
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25,857-SF tear-off to the metal deck
The existing Duro-Last membrane and polyisocyanurate insulation were removed down to the metal roof deck. Tear-off was phased daily so each opened area was dried in before the end of the shift and the tenant spaces below were never left exposed.
-
Deck replacement and rust inhibition
With the deck exposed, 240 square feet of W-type metal decking was found rusted completely through beneath the long-leaking membrane, with daylight visible through the corrosion holes. That decking was cut out and replaced. The remaining deck carried only light surface rust and was structurally sound, so it was wire brushed with a deck preparation tool and coated with red oxide rust-inhibitive primer to stop further oxidation before the new assembly was installed.
-
Slope correction and drain reconstruction
R-20 polyisocyanurate insulation was installed over the bare deck, and tapered insulation with large water-shedding crickets was built into six major low areas to establish positive drainage. All eight roof drains and their drain pipe connections were rebuilt and integrated into the new assembly.
-
TPO installation, curbs, and penetrations
A mechanically fastened Elevate UltraPly 60-mil TPO membrane was installed over the new insulation. Eleven HVAC curbs were rebuilt and reflashed and 72 pipe and vent penetrations received new pre-molded Elevate flashing so every transition point was reconstructed as part of the warranted system.
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Drainage verification and warranty closeout
The completed drainage corrections were checked after installation to confirm the corrected slopes carried water to the rebuilt drains, and the roof was closed out under a 20-year Elevate Red Shield No Dollar Limit warranty.
Measured Outcome
Results
The completed work replaced a roof system that had reached the end of its useful service life, restored the corroded deck beneath it, and corrected the slope and drainage defects that had caused water to stand on it. The result is a long-term warranted TPO assembly on a sound, rust-inhibited deck that drains to eight rebuilt drains, installed without closing the retail center.
Verification & Documentation
The project record documents the existing roof construction, the basis for the replacement recommendation, completed replacement work, drainage corrections, and manufacturer warranty closeout.
- Core sample — documented the metal roof deck, polyisocyanurate insulation board, and Duro-Last membrane above it
- Tramex moisture survey — non-destructive moisture meter readings were recorded across the roof area to document retained moisture in the existing assembly and support the tear-off recommendation
- Condition record — photographs documented severe membrane shrinkage and seam splitting, loss of the protective upper coating leaving exposed scrim mesh across approximately 20% of the roof, failed seams, extensive prior patching, and persistent ponding
- Tear-off — existing roofing removed completely to the metal deck before the new R-20 PolyISO and Elevate UltraPly TPO system was installed
- Deck repair record — 240 SF of rusted-through W metal decking documented and replaced, and the remaining sound deck wire brushed and coated with red oxide rust-inhibitive primer
- Drainage correction — tapered PolyISO and large water-shedding crickets corrected six major ponding slopes, and all eight drains and drain pipe connections were rebuilt
- Rooftop details — 11 HVAC curbs rebuilt and reflashed and 72 pipe and vent penetrations flashed with new pre-molded Elevate covers
- Manufacturer warranty — 20-year Elevate Red Shield No Dollar Limit warranty issued for the completed roof
- Safety record — 0 recordable incidents during the 21-working-day project while the retail center remained occupied
The project demonstrates why a commercial roof replacement should address the causes of failure rather than the membrane alone: tearing off to the deck exposed corrosion that had gone entirely through the decking, and correcting the six ponding slopes and rebuilding every drain ensured the new assembly drained properly instead of repeating the defect that shortened the life of the previous roof.
Photographic Record
Evidence
Original project photographs document the failing Duro-Last conditions, moisture meter testing, drainage deficiencies, roof tear-off, rebuilt drains and curbs, TPO installation, and the slope correction built into the new insulation layer.
Who Did the Work
Project Team & Credentials
Site Supervision
All field crew members assigned to the project had completed OSHA 30-Hour Construction Safety training, with a designated Fall Protection Competent Person on site for the duration of the work.
Manufacturer Certification
GoTech Roofing held current Elevate manufacturer-authorized applicator status at the time of the work, a requirement for installation of the warranted Elevate roofing system.
Inspection & Reporting
GoTech Roofing commercial roof inspection staff documented the pre-project roof conditions, Roof 1 core sample, Tramex moisture meter survey of Roofs 1 and 2, membrane failures, drainage observations, and roof-by-roof repair or replacement recommendations. Elevate warranty closeout was completed for the two new TPO replacement roofs.
Common Questions
Commercial Roof Replacement & Drainage FAQ
These are the questions commercial property owners and facility managers most often ask when a flat roof is ponding, leaking, or nearing the end of its service life. Each answer explains the general principle so you can evaluate your own building's roof.
Does ponding water on a flat roof mean the roof has to be replaced?
Not always. Ponding is most often a slope and drainage design defect rather than a membrane failure, so standing water alone does not condemn a roof. Industry practice treats water remaining on a roof more than 48 hours after rainfall as ponding, and it accelerates membrane aging, adds structural load, and voids many manufacturer warranties. The correct test is whether the membrane itself is still serviceable and whether the assembly below it is dry. If the membrane is sound, ponding can often be corrected on its own with tapered insulation and crickets. If the membrane has failed, the ponding should be designed out during a full replacement so the new roof does not repeat the defect.
How do you know whether a commercial roof needs to be replaced or just repaired?
The decision should be based on documented condition, not age. A qualified assessment combines a physical core sample to identify the deck and existing assembly, a moisture survey to determine how much water is trapped in the assembly, and a post-rainfall drainage assessment to separate membrane failure from slope defects. Isolated damage on an otherwise sound roof is a repair. Widespread seam failure, a membrane that has lost its protective surface, saturated insulation, or a corroded deck point to replacement, because those conditions will continue to progress underneath any patch or coating applied over them.
What does a roof core sample show?
A core sample is a small full-depth cut through the roof that reveals the deck material, the type and thickness of insulation, whether that insulation is wet, and how many roofing systems have already been installed. That information determines whether a new roof can legally and practically be installed over the existing one, what fastener lengths and attachment method the new system requires, and what R-value already exists. The core is patched the same day it is taken.
What is a Tramex moisture meter survey and why is it done before a roof replacement?
A Tramex moisture meter survey is a non-destructive scan that measures the electrical impedance of a roof assembly to locate moisture trapped in the insulation and substrate. It is performed before replacement because wet insulation cannot be roofed over: a recover installed above saturated material will trap the moisture, degrade the insulation's R-value, corrode a metal deck, and void manufacturer warranty coverage. The survey maps which areas are wet, which determines whether the roof is a candidate for recover or requires a full tear-off.
Can a new commercial roof be installed over an existing one?
Sometimes, but only under specific conditions. Building codes generally limit a roof to two total roofing systems, and a recover is only appropriate when the existing assembly is dry, structurally sound, and adequately sloped. A recover also leaves the existing slope in place, so it cannot resolve ponding. When a second roof is already present, when moisture testing shows a saturated assembly, or when the deck below has corroded, a full tear-off to the deck is the only compliant option.
How is ponding water fixed without replacing the entire roof?
Ponding is corrected by rebuilding the slope rather than the membrane. Tapered polyisocyanurate insulation is added in the low areas and feathered out into the roof field, and water-shedding crickets are constructed to divert runoff toward drains, scuppers, or the gutter edge. The new work is then tied into the existing membrane. Deteriorated drain bodies and drain pipe connections are typically rebuilt at the same time, since restoring slope accomplishes little if the outlets the water is directed to are themselves blocked or leaking.
What does a commercial TPO roof replacement assembly include?
A complete TPO replacement is more than a new membrane. It includes tear-off to the deck, repair or replacement of any deteriorated decking, new insulation to the specified R-value, slope correction where drainage is inadequate, rebuilt drains, reconstructed HVAC and vent curbs, new flashing at every penetration, and new perimeter edge metal. The membrane is then attached mechanically or fully adhered depending on the deck type and wind-uplift requirements. A proposal that prices only the field membrane is not a complete replacement.
How long does a commercial TPO roof replacement take on an occupied building?
Schedule depends on roof area, tear-off volume, and how much rooftop equipment, deck repair, and drainage work is involved, but a properly staged replacement can proceed without closing the building. The roof is opened in sections small enough to be torn off, insulated, and dried in within the same shift, so no area over occupied space is left exposed overnight. Staging, material hoisting, and hot work are coordinated around business hours, and tenants are notified in advance of work directly above their space.
What happens if a metal roof deck has rusted through under a leaking roof?
Corroded metal decking has to be replaced, not roofed over. Prolonged leakage keeps the deck wet and oxidation eventually perforates the steel, at which point it no longer provides a structural substrate or a sound base for fasteners. Because the condition is hidden beneath the membrane and insulation, it is usually discovered only once tear-off exposes the deck, which is one reason deck repair should be addressed as a unit-price allowance in the contract. Perforated sections are cut out and replaced with matching new deck, while surrounding deck that shows only light surface rust is wire brushed with a deck preparation tool and coated with a rust-inhibitive primer to slow further oxidation before the new assembly is installed.
What is an Elevate Red Shield NDL warranty?
NDL means No Dollar Limit. An Elevate Red Shield NDL warranty provides manufacturer-backed coverage for covered conditions during the warranty term without a repair-cost cap tied to the original contract value, subject to the warranty terms and exclusions. It requires the manufacturer to inspect and approve the completed roof, and it is only available through manufacturer-authorized applicators, which is why the installing contractor's Elevate licensing status matters on a warranted commercial roof.
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