Project type · Commercial
Parapet and scupper drainage on a commercial building
Flat and low-slope roofs behind parapet walls do not take conventional gutters. They drain through scuppers, and the overflow provisions are a code matter rather than a preference.
What is actually going on
A parapet wall means water cannot simply run off the edge. It has to leave through a designed opening, and if that opening blocks, the water has nowhere to go but onto the roof structure.
Ponded water is heavy. That is why overflow provisions exist on parapet roofs — so a blocked primary path cannot load the structure.
It is also why this is not a job to give to a residential-only gutter company. Getting it wrong on a commercial building is a structural question, not a cosmetic one.
How we work it out
Diagnosis before quote.
Identify the primary drainage path and confirm whether a secondary or overflow provision exists and is clear.
Assess the roof area draining to each opening and whether the capacity is realistic for a monsoon burst rather than an average day.
Check where the water goes once it leaves the wall — commercial discharge frequently needs to be taken somewhere specific.
How we approach it
- Scupper and through-wall work executed under our Arizona ROC CR-45 licence, which covers commercial as well as residential sheet metal.
- Overflow provisions treated as a requirement rather than an upgrade.
- Large-capacity runs and downspouts sized to the actual roof area.
- Site drainage where roof water has to be carried away from the building.
- Certificate of insurance and additional insureds provided as your contract requires.
What to watch for in any quote
Including ours. These are the things worth asking about:
- A contractor holding a residential-only sheet metal classification bidding commercial work
- No secondary or overflow provision on a parapet roof
- Primary scuppers partially blocked and never inspected
- Capacity sized for average rainfall rather than a monsoon cell
Think this is your house?
Free estimate and an honest diagnosis — including telling you if it is something other than gutters.