Skip to content Flat roofing problems don’t improve on their own — a failed seam gets worse with every rain. Reach out and we’ll schedule a free assessment, walk the roof with you, and give you a clear written scope of what needs to be done and what it costs.
Flat and low-slope roofs require a completely different system than steep-pitch shingles — water doesn’t shed by gravity alone, so the membrane must be fully waterproof and heat-welded at every seam. At Top Quality Exteriors, we install TPO (thermoplastic polyolefin) membrane systems on commercial buildings, commercial additions, and residential flat-roof sections across the St. Louis metro. TPO is the most widely installed flat-roofing membrane in the industry today because of its heat-welded seams, reflective white surface, and 15-to-20-year manufacturer warranties.
We also install EPDM (rubber membrane) for projects where cold-temperature flexibility is the priority, and modified bitumen for built-up flat roof systems on older commercial buildings in Maryland Heights and St. Peters. The right system depends on roof dimensions, existing insulation, drainage configuration, and budget. Homeowners and building owners weighing options often start with a commercial roofing consultation to match the system to the specific project parameters before committing to a material.
The three main flat-roofing systems each have a distinct performance profile, and the right choice depends on your building type, budget, and local climate demands. TPO is heat-welded thermoplastic — the seams are fused together, not glued or lapped, which means the joint is chemically bonded and as strong as the membrane itself. It’s reflective white by default, which matters in St. Louis where commercial buildings absorb significant heat load through a dark roof in summer. EPDM is a rubber membrane that stays flexible in Missouri’s cold winters and is easier to patch — good for buildings with complex rooflines or existing EPDM systems. Modified bitumen is a hybrid system used primarily on built-up roofs — common on older commercial buildings in O’Fallon and St. Peters where the existing system is built-up asphalt. We assess each roof and recommend the system that fits the structure, not the one with the highest margin. A roof repair is sometimes the right answer before a full replacement, and we’ll tell you when that’s the case.
Every flat roofing project follows five steps — from the initial assessment through the final seam inspection and warranty documentation. There are no shortcuts in a properly installed TPO system. Here’s what to expect from our crew on your project.
We walk the roof and check membrane, seams, and drainage. Our estimator flags ponding, failed seams, and wet insulation. You receive a written quote before scheduling any work.
Existing membrane and insulation are stripped to the deck. The deck is probed for rot, failed fasteners, and delamination. Damaged areas are replaced before new material is set.
New polyiso board is fastened to the deck at required thickness. Joints are staggered to eliminate continuous seams below. This sets the thermal barrier under the new membrane.
TPO membrane is rolled out and heat-welded at every seam. Penetrations, drains, and edge details are flashed and welded. All seams are hand-probed after welding to confirm fusion.
We probe every seam for voids and incomplete welds. Drains are cleared and drainage flow is confirmed across the roof. You receive a written report with manufacturer warranty docs.
Flat roofing is a specialized trade — mistakes in seaming, drainage slope, or insulation spec all cause expensive interior damage within a season. Top Quality Exteriors has been installing and maintaining flat roofing systems across the St. Louis metro for over 12 years, and our crews are trained in TPO, EPDM, and modified bitumen systems. We spec the right system for each project and install it to manufacturer standards to preserve the full material warranty.
We’re fully licensed and insured in Missouri, and every flat roofing project comes with a written workmanship warranty on labor separate from the manufacturer’s material coverage. We also perform maintenance inspections and seam repairs on existing flat roofs for commercial building owners in Maryland Heights and St. Peters — so you have a single contractor for new installations, repairs, and annual maintenance walkthroughs throughout the life of the roof.
TPO flat roofing in the St. Louis area typically runs between $5 and $12 per square foot installed, depending on membrane thickness, insulation requirements, number of penetrations, and whether the existing system requires a full tear-off. A 2,000-square-foot flat roof in the $10–$12 range is common when new insulation and full membrane replacement are required. EPDM is typically priced similarly to TPO; modified bitumen runs slightly higher due to the multi-ply labor requirement.
The long-term cost of doing flat roofing wrong is much higher than the cost of doing it right the first time. A failed seam allows standing water that damages insulation, structural decking, and eventually interior finishes — repairs that exceed the original roofing cost. We provide written quotes with full line-item detail and will walk you through the system options and cost differences so the decision is yours to make with clear information in hand.
Every credential we carry is a commitment to quality, safety, and your peace of mind — on every project, in every state we serve.
