Flat Roofing Services in St. Louis, MO

CGR Legacy Construction helps St. Louis-area commercial property owners and managers evaluate, repair, restore, re-cover, and replace flat / low-slope roof systems. We focus on the conditions that matter most on these roofs—drainage, membrane condition, seams, flashings, penetrations, rooftop details, and the underlying roof assembly—so you can choose the right next step instead of guessing.

Most “flat” commercial roofs are actually low-slope systems designed to move water toward roof drains, scuppers, gutters, or other drainage points. The right repair or replacement path depends on the existing roof system, drainage, moisture / substrate condition, details, building use, and long-term goals.

Flat Roofs Are Really Low-Slope Roof Systems

Commercial roofs often look flat from the ground, but most are built with a slight slope so water can move toward drains, scuppers, gutters, or other discharge points. Because water moves more slowly across a low-slope surface, the roof depends heavily on membrane continuity, sealed seams and transitions, properly detailed penetrations, and a drainage plan that keeps water moving.

  • Low-slope roof: industry category generally used for roof systems at slopes of 3:12 or less.
  • Roof membrane: the primary weatherproof layer—such as TPO or another low-slope roof covering.
  • Roof assembly: more than the membrane; it may include deck, vapor control, insulation, cover board, membrane, flashings, fasteners / adhesives, drains and edge details.
  • Positive drainage: the roof is shaped / detailed so water is directed toward drainage points rather than remaining in broad low areas.

How a Flat Roof Moves Water

Drainage is one of the most important educational themes on this page. Build a visual showing a simple low-slope roof plane guiding water toward drains / scuppers and show where tapered insulation or crickets may be used to help direct flow.

Roof drain

Internal drain that carries water through the roof / plumbing system. Blocked or poorly located drains can contribute to standing water.

Scupper

Opening through a parapet / wall that lets roof water discharge. Scupper condition and placement affect perimeter drainage.

Gutter / downspout

Perimeter collection and discharge system on certain low-slope roofs. Clogs, poor slope, or undersized / damaged components can affect water movement.

Tapered insulation

Insulation manufactured in varying thicknesses to create slope. Can help direct water toward drains on new / reroof assemblies.

Cricket / saddle

Small built-up slope used to divert water around equipment or toward drainage. Helps reduce water trapping behind curbs and other obstacles.

Ponding water

Water that remains on the roof after rain instead of draining efficiently. Recurring ponding deserves investigation; cause may be drainage, deflection, blockage, or surface / slope conditions.

Flat Roof Anatomy

Common Flat Roof Problems & What They Can Mean

Active leak / ceiling water

Entry may be at a seam, penetration, curb, flashing, drain, edge, puncture, or another location away from the visible interior drip.

Ponding / standing water

Drainage blockage, inadequate slope, deflection, low area, surface irregularity, or drainage-layout issue may be involved.

Open seam / lap

A welded, taped, adhered, or asphaltic seam / lap may be separating or deteriorating.

Puncture / cut / tear

Foot traffic, tools, service work, hail / debris, or rooftop activity may damage the membrane.

Flashing / curb leak

Transitions around walls, equipment curbs, vents, pipes, or other penetrations can become entry points.

Parapet / coping issue

Perimeter metal, joints, base flashing, or wall transitions may be damaged or open.

Blisters / splits / surface deterioration

Some asphaltic or older roof systems may show age-related surface distress or trapped-moisture indicators.

Wet / soft roof areas

Insulation, cover board, or deck may be affected; scope depends on what investigation confirms.

Repeated patches

A roof can reach a point where continued localized repairs no longer create dependable performance.

Aging but mostly intact roof

May be a candidate for targeted repair, re-cover, or liquid-applied restoration depending on condition and compatibility.

Flat Roof Problems Usually Start at Details, Drainage, or Membrane Damage

The water showing up inside a building does not always sit directly below the roof entry point. On a low-slope roof, water can travel along insulation, deck lines, fasteners, seams, or interior construction before it becomes visible. That is why the first job is to identify the actual source and understand whether the problem is localized or part of a broader roof-system condition.

TPO - Featured

Thermoplastic single-ply membrane with heat-welded seams. Featured membrane option for replacement / reroof / some recover assemblies.

Polyurethane / elastomeric liquid-applied coating

Fluid-applied elastomeric polyurethane system used for restoration / waterproofing on compatible, properly prepared roofs. Budget-conscious restoration / life-extension pathway when the existing roof qualifies.

EPDM

Synthetic rubber single-ply membrane typically detailed with seam tape / accessories. Explain as a common existing / industry system owners may encounter.

PVC

Thermoplastic single-ply membrane with heat-welded seams. Explain as another common thermoplastic low-slope system.

Modified bitumen (SBS / APP)

Polymer-modified asphalt membrane system available in multiple installation methods. Useful for identifying existing systems and industry alternatives.

Built-up roofing (BUR)

Multi-ply asphalt / reinforcement roof system. Useful as an existing-roof / legacy-system category.

Metal low-slope / retrofit

Structural or retrofit metal roof application. Keep mostly on Commercial Roofing / replacement pages; not the core “flat roof” focus.

TPO Roofing for Commercial Flat & Low-Slope Roofs

TPO is a thermoplastic single-ply membrane commonly used on low-slope commercial roofs. Its seams are heat-welded, and reflective membrane options are widely used on commercial buildings. CGR should position TPO as a major system to compare when a roof needs replacement or a qualified re-cover—but not as an automatic answer for every building.

Can a Flat Roof Be Restored Instead of Replaced?

Sometimes. If the existing low-slope roof is still a suitable candidate, a liquid-applied elastomeric coating can be a lower-upfront-cost restoration path that protects the existing roof and extends useful service life without immediately tearing off the full system. CGR currently offers a polyurethane / elastomeric coating pathway on qualifying roofs. The roof still needs to be evaluated first, known leaks and defects need to be addressed, and compatibility / preparation requirements depend on the coating system and existing substrate.

Good restoration candidate may include

Reasons coating may NOT be the right answer

The Right Flat-Roof Solution Depends on the Existing Roof

Some commercial flat roofs need a focused repair. Others can be restored with a compatible coating. Some may qualify for a re-cover, while others are better candidates for full tear-off and replacement. CGR should inspect the roof, understand the existing system and drainage, document visible conditions, and build the recommendation around the actual building instead of forcing every roof into the same solution.

What affects the recommendation

  • Existing roof system and number / type of existing layers.
  • Location and extent of active leaks or known damage.
  • Drainage performance, ponding areas, drains, scuppers, gutters, crickets, and roof geometry.
  • Visible membrane, seam, flashing, penetration, curb, parapet, and perimeter condition.
  • Known or suspected moisture / insulation / substrate issues.
  • Deck / structural condition when investigation exposes or confirms it.
  • Rooftop equipment, foot traffic, solar / supports, and future building use.
  • Project budget, capital horizon, desired warranty / lifecycle, and operational constraints.
  • Applicable code and manufacturer system requirements.

A Flat-Roof Assessment Should Look Beyond the Visible Leak

Drainage is one of the most important educational themes on this page. Build a visual showing a simple low-slope roof plane guiding water toward drains / scuppers and show where tapered insulation or crickets may be used to help direct flow.

Roof field / membrane

Punctures, tears, splits, surface deterioration, prior patches, open details, foot-traffic areas

Seams / laps

Open or questionable seams, weld / tape / lap condition, T-joints / transitions as relevant

Drains / scuppers / gutters

Blockage, discharge path, low areas, ponding, strainers, perimeter drainage

Curbs / penetrations

HVAC curbs, vents, pipes, conduits, supports, pitch pockets / pans where present, flashing transitions

Parapets / walls / coping

Base flashing, terminations, coping joints, edge / wall transitions, scupper details

Insulation / substrate indicators

Soft areas, compressive damage, suspicious moisture conditions; further testing only if included / qualified

Perimeter / edge

Edge metal, terminations, wind / storm damage, membrane securement details visible from the surface

Rooftop equipment / traffic

Service paths, dropped tools, support points, grease / chemical exposure, maintenance activity

Prior repairs / coatings

Compatibility, adhesion / failure concerns, patch history, transitions between materials

Commercial Flat-roof Process

1. Initial Property Discussion

Building use, active leaks, roof history, system if known, urgency, access, occupants / tenants, project timeline.

2. Roof Assessment

Walk and document the membrane, drainage, seams, flashings, curbs, penetrations, parapets / edges, prior repairs, and visible problem areas.

3. Define the Decision Path

Explain whether the roof appears best suited for repair, restoration / coating, re-cover, replacement, or further investigation.

4. Scope & Estimate

Define the proposed work, assumptions, materials / system, exclusions, access / staging, schedule, and any concealed-condition contingencies.

5. Execute the Work

Coordinate the repair, restoration, re-cover, or replacement around weather, access, safety, rooftop equipment, and building operations.

6. Final Review & Closeout

Review completed work, punch items, photos, warranty / maintenance information when applicable, and future inspection recommendations.

Real CGR Flat-Roof Project Proof

Review documented residential roofing work and real feedback about communication, recommendations, workmanship, cleanup, and the overall experience.

  • City / market
  • Service and homeowner problem
  • What CGR found
  • Work completed and result
"Highly recommend CGR! They worked really well with my insurance company, did very great work! Very good company through and through! will definitely be going back for future work!!"
Savannah Kinion
Reviewed via Facebook
"Great company! Takes pride in their work and goes above and beyond for their costumers!"
Daniel Carver
Reviewed via Facebook
"Not knowing what i needed or how bad it was, my roof needed attention.. CGR Legacy was there to help - AJ (a contractor) for the company came out was honest and helpful. Definitely recommend them. And appreciate them."
Stephanie Ellis
Reviewed via Google
"We hired CGR Legacy Construction for a commercial roofing project and couldn’t be happier. Their team provided a full inspection and detailed report before starting. The project was completed on schedule and within budget. Great communication throughout. Definitely a top commercial roofing company in the St. Louis area."
Curt Ketchum
Reviewed via Google
  • City / market
  • Service and homeowner problem
  • What CGR found
  • Work completed and result

Flat Roofing Across St. Louis & St. Charles

CGR Legacy Construction provides commercial flat and low-slope roofing services across St. Louis, St. Charles, and surrounding Missouri communities. Service availability can depend on property type, roof system, scope, access, project size, scheduling, and current production capacity. Contact CGR to confirm the building and project.

Flat Roofing FAQ

“Flat roof” is the common search term, but most commercial roofs that look flat have some slope built into the roof or roof assembly to move water toward drains, scuppers, gutters, or other drainage points. Roofing professionals typically refer to these as low-slope roof systems.

Common low-slope systems include TPO, PVC, EPDM, modified bitumen, built-up roofing, liquid-applied systems, and certain metal / retrofit assemblies. CGR should only market systems as installed services after that capability is confirmed.

Standing water can be related to blocked drains or scuppers, low areas, inadequate slope, structural deflection, surface irregularities, or drainage design / maintenance issues. The cause should be evaluated rather than assumed from the water alone.

Yes. Localized leaks, punctures, seams, flashings, or other defects may be repairable when the surrounding roof remains serviceable. The assessment should determine whether repair, restoration, re-cover, or replacement is the better path.

TPO is a thermoplastic single-ply membrane widely used on low-slope commercial roofs. Its seams are heat-welded, and it is available in reflective membrane options and multiple approved installation configurations.

Sometimes. A compatible, serviceable roof may be a candidate for a liquid-applied elastomeric coating after defects are repaired and the surface is properly prepared. CGR offers a polyurethane / elastomeric coating pathway on qualifying roofs; the exact product and preparation requirements are project-specific.

No. Polyurethane / elastomeric liquid-applied roof coatings and spray polyurethane foam roofing are different systems. CGR should use the exact product / system terminology for the coating being proposed.

Potential leak locations can include seams, penetrations, HVAC curbs, base flashings, parapets, coping / edge details, drains, scuppers, punctures, and damaged membrane areas. The visible interior drip may not be directly below the roof entry point.

A reroof can create an opportunity to address drainage using strategies such as tapered insulation, crickets, drain / scupper work, or other assembly changes when the roof design, structure, code, and project scope support them.

CGR serves commercial properties in St. Louis, St. Charles, and nearby Missouri communities. Contact the team to confirm the property location, roof type, and project scope.

Get Clear Answers About the Flat Roofing

If you are seeing a ceiling stain, active water, a recurring leak, missing shingles, or moisture after a storm, start by finding the roofing source. CGR will inspect the roof, explain what we find, and help you understand whether the next step is a targeted repair or broader roofing work.