Aluminium Vertical Threaded Roof Drain Outlet with Dome Grate – New-Build Flat Roof Drainage, 50-150mm

Every flat roof needs somewhere for water to go, and on a new build or full re-roof the outlet is worth getting right the first time — it's bonded or bolted into the membrane before anything else goes down, and a poor-quality or wrongly-sized one is a genuinely awkward thing to replace later. This is a cast aluminium vertical outlet with a raised dome grate: a female-threaded spigot that connects directly into standard rainwater pipework, supplied complete with its clamping ring and grate in one assembly.

The dome grate sits proud of the roof surface, which keeps leaves and debris away from the throat of the outlet far better than a flat grate — a real advantage under trees or on roofs that don't get cleared often. Cast aluminium construction resists corrosion far longer than the galvanised or plastic outlets it's commonly specified to replace, and the female-threaded spigot means a standard downpipe simply screws straight in without special adaptors.

Key benefits

• Cast aluminium construction — corrosion-resistant, long design life
• Raised dome grate keeps leaves and debris clear of the outlet throat
• Female-threaded spigot (to BS21) connects standard rainwater pipework directly, no special adaptors
• Supplied complete with clamping ring and grate as one assembly
• 4 diameters covering domestic to larger commercial flow rates

Where it's used

New-build and full re-roof installations on EPDM, GRP or other single-ply flat roofing where the outlet is being bonded or fixed into a new membrane at construction stage — garages, extensions, commercial units and larger flat roofs. If you're replacing a failed or leaking outlet in an existing roof without disturbing the surrounding membrane, our Aluminium Flat Roof Refurbishment Drain Outlet is the clamp-ring retrofit version designed for that job instead.

Specification

Ordering & installation guidance

Size the outlet to your roof's drainage design — as a rough guide, 50mm and 75mm suit smaller domestic roofs, while 100mm and 150mm are specified on larger commercial and multi-outlet roofs; always check against your roof's calculated flow rate rather than roof area alone for anything beyond a straightforward domestic job. The outlet is bonded into the membrane using the compatible adhesive for your roofing system — for EPDM installations, pair with our EPDM Water-Based Deck Adhesive or EPDM Rubber Roofing Contact Adhesive, following the outlet manufacturer's bonding detail. A standard rainwater downpipe simply threads directly into the spigot.

FAQ

What size do I need?
Outlet sizing depends on your roof's drainage design (area, rainfall intensity and number of outlets), not just roof size — for anything beyond a small domestic roof, check the sizing against building regulations Part H guidance or a drainage calculation rather than guessing.

Does this come with the clamping ring and grate?
Yes — the outlet, clamping ring and dome grate are supplied together as one complete assembly.

Can I use this to replace an existing outlet without disturbing the roof?
This threaded outlet is designed to be bonded into a new membrane at installation. For a retrofit into an existing roof, our clamp-ring refurbishment outlet is the better fit.

Is it compatible with EPDM and GRP roofs?
Yes — the outlet itself is roofing-system-agnostic; it's bonded or sealed into the membrane using the adhesive/detail appropriate to whichever system you're installing.

How is it delivered?
Despatched from UK stock via courier — check the product page at checkout for the current delivery estimate to your postcode.