What is a side outlet?
A side outlet, also called a scupper outlet or parapet outlet (in Dutch zijuitloop), drains rainwater from a flat roof horizontally through the roof edge, upstand or parapet. Outside, the water discharges into a rainwater hopper and from there into the downpipe. The alternative is a vertical roof outlet, which takes the water down through the roof deck.
Construction
- Spout or box: usually a rectangular or round tube made of plastic, zinc, copper or aluminium.
- Flange: a flat plate on the inside that lies on the roof surface and against the upstand. The roof covering is bonded over this flange.
- Fall: the spout slopes slightly outwards, so water runs away freely and does not stand in it.
Installation in brief
- Position the outlet at the lowest point of the roof. The fall of the roof must run towards it.
- Form an opening in the upstand or parapet, slightly larger than the spout.
- Push the spout through from the roof side, so the flange lies on the roof.
- Bond the roof covering over the flange and upstand following the system manufacturer’s instructions.
- Fit the hopper outside and connect it to the downpipe.
Practical points
- Lowest point: if the outlet is too high, water ponds on the roof. This loads the structure and ages the roof covering faster.
- Capacity: the number and size of outlets depend on the roof area. If in doubt, have it calculated by the supplier or a drainage specialist.
- Emergency overflow: a roof with upstands needs an emergency overflow, so water cannot build up unnoticed if an outlet blocks.
- Leaf guard: a grating in front of the outlet keeps out leaves and debris. Check it in autumn.
Related terms
- Vertical roof outlet
- Roof outlet
- Emergency roof drain
- Parapet
- Rainwater drainage
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