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GRP Roofing Outlets — Soil Pipe, Rainwater Drain, Through-Wall & Flat Drain

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About GRP Roofing Outlets & buying advice

Shop GRP flat roof outlets including the 80mm water soil pipe outlet, 70mm rainwater vertical drain outlet, GRP through-wall parapet outlet trim, and GRP rainwater outlet. Choose the correct outlet for the drainage route before laminating — outlets are glassed into the GRP system during installation.

Buying guide

Choose GRP Roofing Outlets for finishing GRP roof edges, corners, wall details, drainage points or perimeter details.

Good choice when

  • Use this category for finishing GRP roof edges, corners, wall details, drainage points or perimeter details.
  • Use it when the surface is GRP roofing systems and prepared flat roof details.
  • Use it when the measurements, preparation work and related accessories have been checked.

Consider another route when

  • Do not use this category when you need the main GRP kit, resin or roof covering rather than roof edge detailing.
  • Do not use it when the roof is unsafe or unsuitable without preparation.
  • Do not use it as a shortcut if another CRS system is a better fit.

Next step: Match the trim or outlet to the roof edge, wall detail, corner or drainage point before ordering.

Why The Outlet Must Be On Site Before Laminating

GRP roofing outlets are not surface-fitted accessories — they are built into the laminate. The outlet is positioned in the deck opening before the GRP is applied, and the laminate is then applied around and over the outlet flange, glassing it permanently into the waterproofing system. If the outlet is not on site when lamination starts, a hole in the completed laminate has to be cut and the outlet retrofitted with bonded patches — a repair that is never as strong or as clean as the original installation.

Parapet vs Vertical Drainage

A roof draining through a parapet needs a horizontal through-wall outlet that penetrates the parapet face. The GRP parapet outlet trim creates the GRP-to-wall junction detail, which is then sealed and weatherproofed. A roof draining vertically through the deck to a pipe below uses a vertical pipe outlet sized to match the pipe diameter. The two drainage types are architecturally common in different situations — check the roof drawings to confirm which type applies before ordering.

Frequently asked questions

What is the difference between a soil pipe outlet and a rainwater drain outlet?

Both are for vertical drainage through the roof deck into a downpipe. The soil pipe outlet is 80mm diameter; the rainwater drain outlet is 70mm. Match the outlet to the pipe diameter on site.

When should I use a through-wall parapet outlet?

When the roof drains horizontally through a parapet wall rather than vertically through the deck. The parapet outlet trim creates the GRP detail at the wall penetration point.

Can a GRP roofing outlet be fitted after the roof is laminated?

Outlets should be fitted before lamination so they can be glassed into the system properly. Retrofitting into cured GRP requires cutting, patching and bonding — it can be done but it is a repair job rather than a clean installation.

Do roofing outlets need to be sealed as well as glassed in?

The GRP laminate applied around the outlet flange provides the primary seal. Some installations also use GRP bandage tape around the outlet edge before the main mat layer for additional reinforcement at the junction.

My roof drains to a gutter at the eaves — do I need a GRP outlet?

No. A roof draining freely over the edge into a standard gutter does not require a GRP drainage outlet. Outlets are only needed where water leaves the roof through a penetration in the deck or parapet.

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