Before replacing a flat or low-slope TPO roof, a roofing contractor should tell you which license the job requires, how the roof will drain, how rooftop equipment and walls will be flashed, what goes under the membrane, and which inspections the building department will make. TPO is a single-ply membrane, meaning it is applied in one layer, so almost every leak comes from a detail: a drain, a seam, an edge or a penetration. Ask about the details, not just the membrane.
The license comes first
Low-slope work has its own license class in Denver. The city’s Roofing Guide requires membrane roofs to be installed by a D-Roof Covering/Waterproofing licensed contractor; a shingle-only license covers just small membrane areas on a shingle job, under 10 percent of the roof or two squares. In Colorado Springs and El Paso County, the Pikes Peak Regional Building Department licenses roofing as a single-trade specialty, and any repair or replacement over 100 square feet needs a permit.
Seven things the contractor should explain
- Drainage. New membrane roofs need a minimum design slope of 1/4 inch per foot. On a reroof, an existing roof that drains within 48 hours does not have to be rebuilt to that slope. Ask where water will go and how fast.
- Drains and scuppers. Where a roof has parapets and drains, secondary overflow drains or scuppers are required, the same size as the main drain and set 2 inches above it. Emergency scuppers need at least a 4 inch opening. A reroof with positive drainage does not have to add them.
- Rooftop equipment. In Denver, units sit on 8 inch legs or an 8 inch curb bearing on the deck, flashed in. No pads or slip sheets.
- Walls and parapets. Wall finishes must stop at least 8 inches above a low-slope roof, and parapets need a noncombustible, weatherproof coping.
- Flashing. Single-ply flashing is installed to the membrane manufacturer’s latest instructions. Ask how the edges, curbs and pipes will be flashed.
- What goes under it. Insulation, a cover board, and how the membrane is attached. If the deck or insulation is exposed on a roof with no cavity insulation, Denver’s energy code requires adding it (R-30 continuous above, or R-38 below a flat deck).
- Inspections. Denver requires a pre-inspection on every low-slope roof, a final, and a mid-roof if the pre-inspection calls for one.
Questions to ask about the membrane itself
- Which membrane, what thickness, and what does its warranty cover?
- How are seams joined, and how are they tested?
- How will you handle ponding areas we already have?
- Who services the roof after installation?
A contractor who answers these in writing, with photos of your existing drains, edges and curbs, is one you can hold to the scope. For a homeowner’s porch or patio roof attached to a shingle roof, the same questions apply on a smaller scale.
Where to go next
For commercial buildings, see commercial roofing in Colorado Springs and commercial roofing in Denver. To vet the company itself, use how to choose a roofing contractor in Colorado Springs and six questions for a roof expert. Denver owners can also read what local knowledge changes on a Denver roof.
Integrity Roofing and Painting is veteran-owned and family-run since 1990, an Owens Corning Platinum Preferred contractor with 650+ Google reviews. Call Colorado Springs (719) 488-2800 or Denver (303) 209-0152, or book a free roof inspection; we reach out the same business day.
Sources: City and County of Denver, Roofing Guide and Checklist (updated 4/11/2024); Pikes Peak Regional Building Department, License Types and Reroofing Guidelines (rev. 03/05/2024).
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