Parapet walls and coping joints
Open coping joints and cracked mortar let water into the top of the wall, where it runs down inside the masonry and exits at the roof-to-wall junction. The roof field can be perfect and the building still leaks.
Flat roof repair in St. Louis City, at a glance
STL Roof Repair repairs flat and low-slope commercial roofs across St. Louis City — built-up tar and gravel, modified bitumen, TPO, EPDM and metal — including parapet and coping details, interior drains and scuppers. John Beal Roofing has been family-run since 1947, is BBB A+ rated and appears on Roofing Contractor Magazine's Top 100 list. Inspections and written estimates are no-charge, and the phone at (314) 429-6000 is answered live at any hour.
The commercial building stock in the city is old, layered and mostly masonry. Storefronts on Cherokee and South Grand, warehouses in Midtown and the near north side, four-families, mixed-use corners, churches and school additions — the vast majority of them are low-slope roofs hidden behind a parapet wall, and a great many still carry a built-up tar-and-gravel assembly with two or three roofs stacked on top of the original. That layering is the first thing an owner should understand, because it drives everything about diagnosis and cost.
On a stacked low-slope roof, water does not travel straight down. It gets into a failed detail, runs sideways between plies or between the membrane and an old substrate, and emerges at the nearest interruption — a light fixture, a beam pocket, a wall cavity thirty feet from the actual breach. That is why the usual approach of patching where the ceiling stain is fails so often on city buildings. The breach is almost never above the stain.
Where It Fails
The Details That Actually Leak
Base flashing at the wall
The vertical leg where the membrane turns up the parapet takes the most movement and the most heat. Slipped or unsealed base flashing is the single most common commercial leak we find.
Interior drains and clamping rings
Loose clamping rings, failed lead or sump details, and drains buried under debris turn a manageable rain into standing water on the deck.
Scuppers and through-wall outlets
A blocked or poorly flashed scupper ponds water directly against the parapet, which is the worst possible place to hold it on a masonry building.
Ponding on a dead-flat deck
Older decks sag between bearing points. Water that never drains adds load, degrades the membrane and finds every seam and fastener in that low spot.
Curbs, hatches and rooftop equipment
HVAC curbs, exhaust penetrations, roof hatches and old abandoned penetrations left unsealed account for a large share of the leaks nobody can locate from the ground.
Our Approach
How We Diagnose A Low-Slope Leak
Start at the details, not the stain
We inspect the parapet, coping, base flashing, drains, scuppers and every penetration before we consider the field. That order finds the cause far more often.
Determine how many roofs are up there
Core knowledge changes the recommendation. A roof carrying multiple layers may need a tear-off where a single-ply would take a repair.
Scope repair versus recover versus replace
We tell you which of the three your roof is actually a candidate for, in writing, with photographs of the conditions behind the recommendation.
Handle the water now if it is active
Emergency response is available around the clock for active commercial leaks. Stopping water beats waiting for a scheduled crew.
We install and repair TPO, EPDM, modified bitumen, metal and liquid-applied coating systems, which matters because the right answer varies by building. A warehouse with a large open deck and decent drainage is a straightforward single-ply candidate. A century-old storefront with three layers of gravel, a sagging deck and a shared parapet with the building next door is not, and anyone who quotes it as one without going up there is guessing. Coatings have a real place on a sound roof with good drainage and are a poor answer on a saturated one, and we will say which you have.
There is one city-specific complication worth naming: shared and adjoining walls. In dense blocks, your roof terminates against a neighbor's parapet, and water entering the top of a wall you do not own can appear as a leak in a building you do. We document what we find and tell you plainly where the responsibility line sits, because the alternative — repeatedly patching your side of a wall that is wetting from the other side — is money spent for nothing.
Property managers and apartment owners usually want two things beyond the repair itself: documentation they can file, and a contractor who answers when a tenant calls at midnight. Our inspections come with photographs and a written repair plan, our insurance division handles storm claims and adjuster meetings, and a live dispatcher answers the main line at any hour. Qualifying work carries a lifetime workmanship warranty.
- Free commercial inspection with photographs and a written repair plan
- Built-up, modified bitumen, TPO, EPDM, metal and coating systems
- Parapet, coping, base flashing and roof-to-wall detail repair
- Interior drain, sump and scupper repair and clearing
- After-hours emergency response for active commercial leaks
- Storm damage documentation and insurance claim representation
Common Questions
What Building Owners Ask Us
The stain is in the middle of my ceiling. Why are you inspecting the parapet?
Because on a low-slope roof water rarely enters directly above where it appears. It gets in at a detail, travels between layers or down inside the masonry, and comes out at the first interruption it finds. Chasing the stain is how buildings get patched five times without the leak stopping. We work the details first because that is where the cause almost always is.
Can my roof be coated instead of replaced?
Sometimes, and it is a legitimate option on a structurally sound roof with functioning drainage and dry insulation. Coating a roof that is already holding water inside the assembly just seals the moisture in and buys a year. We check whether the substrate is dry before we recommend it, and we will tell you if coating is the wrong call for your building.
How many layers of roofing can be on there?
On older city buildings, commonly two or three. It matters because code and load limits eventually require a full tear-off rather than another recover, and because each added layer makes leak tracing harder. Establishing what is actually up there is part of the inspection, and it changes the price and the plan honestly rather than after work starts.
Do you respond to commercial leaks after hours?
Yes. A live dispatcher answers (314) 429-6000 twenty-four hours a day and we dispatch for active commercial leaks, including ponding on a membrane roof, which adds significant load to the deck. Response windows depend on weather and call volume, and you will get a realistic one on the phone rather than a promise.
Will insurance cover a commercial flat roof claim?
It can, when an inspection documents legitimate storm damage such as hail impacts or wind damage to the membrane and flashings. It depends entirely on the policy and what the adjuster verifies. Our insurance division documents the damage and represents the claim, but payouts are never guaranteed and deductibles are never waived.
Free Roof Inspection
Tell us what is going on and we will call to schedule. Inspections are free.
Related
Related Commercial & City Pages
Leak On A City Flat Roof?
Get it looked at before the next storm loads it up. Commercial inspections and written repair plans are no-charge, and after-hours dispatch is available.