(214) 807-0414Request an assessmentDrainage guide
Low-slope roofs are built with fall in them. Current codes generally require a minimum slope toward drainage, achieved either by sloping the structure or by building fall above it with tapered insulation. What sits on many older buildings is a roof that started close to level, has deflected since, and now holds water wherever the deck sagged first. Standing water is a design failure making itself visible.
In short
Internal drains, scuppers and gutters carry the design rainfall off the roof. What matters is not how many outlets exist but whether water can reach them. A drain sitting slightly proud of the field around it collects nothing and tells you nothing.
01
Standing water is heavy, and a shallow pond across a wide bay is a real load on a structure already carrying the roof, the equipment and whatever the last owner put up there. Deflection creates the pond and the pond deepens the deflection. That loop runs quietly for years before anyone thinks to measure it.
02
Where the structure cannot be re-sloped, fall is built above it. Tapered insulation creates the planes, and crickets divert water around curbs and up-slope of equipment. That layout is a design exercise with a drawing behind it. Laying flat board and hoping is how a brand new roof arrives with the old ponds still in it.
03
Most drainage-related failures start at a strainer packed with leaves, a scupper blocked with gravel, or a downspout discharging into a line that stopped flowing below the roof. Clearing outlets ahead of the wet season is the cheapest work available on a commercial roof and the first item cut from a budget.
Questions
The commonly cited benchmark is that water should be gone within about forty-eight hours of rainfall in drying conditions. Water still standing beyond that is not a puddle, it is a drainage or structural defect, and the cause is worth locating rather than tolerating.
Sometimes, and it is substantial work: cutting the deck, running pipe inside the building, and coordinating with the tenancy below. Cutting a scupper through a parapet is often the less invasive answer where the geometry and the wall allow it.
Because the outlets keep up until they do not. A drainage system sized or blocked to the point where it only fails under intensity produces exactly that pattern, and the entry point is often nowhere near the drain that caused it.
Frequently, and it is worth reading before it becomes relevant. Single-ply system warranties commonly exclude damage attributable to standing water, or condition coverage on drainage being maintained, and some name a period beyond which water remaining on the roof is treated as a design matter rather than a product one. This is among the more consequential paragraphs in a warranty document and among the least read. Find out what yours says while the roof is still new enough for the answer to change something.
That is a lease question and the roof has no opinion about it, which is precisely the problem: where it is unassigned, the strainers stay full. Whatever the lease says, someone has to actually do it and someone has to be able to show it was done. Name the party, name the frequency, and keep a dated record of each clearance. A blocked drain that nobody owned is a common and entirely avoidable route to a large repair.
Assessment request
Short, routing-only questions. Nothing here asks you to diagnose the roof yourself.