The Flat Roofing Shop
GRP Through Wall Outlet – Parapet Drain (520mm)
GRP Through Wall Outlet – Parapet Drain (520mm)
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Horizontal parapet outlet for GRP flat roofing systems.
The GRP Through Wall Outlet is a pre-formed fibreglass parapet drain designed to discharge water horizontally through a wall or upstand.
Manufactured from robust GRP, it integrates directly into the laminate on the deck side and connects to rectangular 65mm x 100mm pipework externally.
Its internal profile follows the D260 Wall Fillet Trim, allowing clean integration at the deck-to-wall junction.
Compatible with GRPROOF 1010, Flexitec, and standard polyester GRP roofing systems.
Application ▸
- Parapet wall drainage
- Balcony drainage where vertical outlets are not suitable
- GRP flat roof perimeter drainage
Used where water needs to drain out through a wall instead of down through the roof.
Why It’s Used ▸
Where gutters are not present and internal outlets are not practical, a through-wall outlet provides controlled discharge without compromising the GRP system.
Using a GRP outlet:
- Ensures full material compatibility
- Allows the flange to be laminated directly into the base coat
- Reduces risk of detailing failure at the drainage point
- Maintains a consistent system build-up
The D260-compatible internal profile ensures the laminate transitions cleanly into the outlet flange.
Installation Overview ▸
- Core or form opening through the wall to suit outlet body.
- Position outlet so internal flange sits flat on the deck.
- Bed in with PU trim adhesive.
- Mechanically fix to the deck.
- Reinforce and laminate the flange joint to surrounding areas with CSM and base resin.
- Consolidate fully to remove air pockets.
- Apply top coat as part of the system.
- Connect external spigot to 65mm x 100mm pipework.
Ensure correct roof falls to direct water towards the outlet.
Specification ▸
- Type: Horizontal Through Wall / Parapet Outlet
- Length Through Wall: Approx. 520mm
- Internal Flange Width: Approx. 300mm
- Upstand Height: Approx. 140mm
- Pipe Compatibility: 65mm x 100mm rectangular outlet
- Material: Hot-pressed GRP
- Colour: Grey
- Compatible With: D260 Wall Fillet Trim, GRPROOF 1010 & Flexitec
Summary ▸
The GRP Through Wall Outlet (520mm) provides a fully compatible parapet drainage solution for fibreglass flat roofs. Designed to laminate directly into the GRP system and connect to 65mm x 100mm pipework, it delivers reliable horizontal discharge without compromising the integrity of the roof.
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