A shingle roof shows hail as bruises, dents, and torn mat. A low-slope section, the part of a St. Louis roof with little or no pitch, usually shows it differently. The damage often sits under the surface of a membrane, and the first sign a homeowner sees is water standing where it never stood before. If the storm came through and the roof looks fine from the yard, that is the wrong test for this part of the house.
What low-slope roofs are made of
Low-slope roofs on St. Louis homes are usually covered with a single-ply membrane, a modified bitumen cap sheet, or a built-up system of layers. These sit on a deck that is often plywood or OSB. The membrane is the waterproof layer, and it depends on the roof being flat enough to send water to drains and scuppers rather than letting it collect. Hail does not have to break through to matter. A strike can crack a seam, scuff a surface coating, or puncture a thin ply, and the water will find that opening before anyone sees it.
Why ponding is the first symptom
Ponding means water that stays on the roof for a day or two after the rain has stopped. On a low-slope section that is a sign the roof is not draining as designed. After hail, the usual causes are a dent or displaced area in the membrane, a drain strainer knocked loose by debris, or a seam that has lifted. Look at the roof the morning after a rain, or the afternoon after a heavy shower, and note where the water sits. A puddle beside a drain is different from a pool in the middle of a flat field, and the two often point to different repairs.
Ponding alone is not proof of hail damage. Standing water can also come from a section built with too little slope, from leaves packed into a drain, or from a deck that has settled over the years. That is why the first step is to record where the water stands, how long it stays, and whether the spot is new since the storm. A photo taken on the day of the storm, if one exists, makes that comparison far easier.
What to check on the walk
Start with the drains and scuppers. Clear leaves and debris by hand, and make sure nothing has been bent or torn free. Do not walk a low-slope roof while it is wet, icy, or still holding standing water, and do not step on any spot that gives under foot. From a safe position, look at the field of the roof for three things: soft areas that feel spongy, dents with a dark or shiny center, and scuffs where the surface coating has been rubbed through. Pay close attention to the seams where two sheets meet and to the edges where the membrane turns up a wall or curb.
Photograph each item with a scale reference, such as a coin or a tape laid flat, and note where it sits on a simple sketch of the roof. A dated photo of standing water taken the morning after a rain is worth more than a photo taken three weeks later on a dry day, because the dry photo shows nothing about how the roof drains.
Where a membrane fails after a storm
- A puncture or tear, often small and round, where something struck the surface
- A seam that has opened or lifted at the lap
- A dent that holds water, which may be shallow but still traps the rain
- A flashing that has pulled away from a wall or curb
- A drain strainer or scupper that is bent, cracked, or sitting loose
Each of these needs a different fix. A small puncture may be patched in place. A lifted seam may need to be reset and sealed. A dent that holds water may call for a larger repair of the field, depending on how the membrane is laid and whether the deck underneath is sound. A roofer should say which of these applies and why, in writing, with the photos and measurements attached.
Freeze and thaw make a small crack bigger
St. Louis winters cycle through freezing and thawing many times in a season. Water that gets into a cracked seam or a small puncture can freeze, expand, and widen the opening. Ice on a low-slope roof also tends to sit longer than it does on a steep one, because there is nowhere for it to slide off. A patch that holds in October may not hold through January. If the storm damage cannot be repaired before the cold arrives, the homeowner should at least record where the standing water sits and note the date of the first hard freeze, so that a later repair has a clear before and after.
Keeping the record that matters
A homeowner dealing with storm damage should keep a plain file: the date of the storm, dated photos of each suspect spot, notes on where water stands after each rain, and a copy of any written scope the contractor provides. A roofing contractor can document the damage, put a written scope with photos and measurements in the homeowner's hands, and attend the inspection as the contractor. The homeowner deals with their own insurer. Missouri law bars a roofing contractor from representing or negotiating a homeowner's insurance claim, and from saying anything about paying, waiving or covering a deductible, so that conversation belongs between the homeowner and the insurer alone.
When to call
If the standing water is new, if a drain is loose, or if the membrane gives under foot in a spot that was firm before the storm, call before the next front arrives. Keys Roofing can be reached at (314) 220-2333. A short walk with a clear list of what was seen is usually enough to decide whether the roof needs a prompt repair or a closer look once the weather settles, and the written notes from that walk are the ones to keep.