Flat roof drainage is commonly project-specific, with different roof constructions, waterproofing systems, building designs, balconies and terraces, all requiring individually tailored solutions.

The Harmer Aluminium Roof Outlet range from Alumasc has been developed to meet these varied requirements, combining unrivalled performance with an extensive choice of outlet configurations suitable for new build and refurbishment projects across commercial, residential and public sector construction.

Designed for use with in-situ concrete, timber and lightweight metal deck roof structures, the Harmer aluminium range is compatible with warm, cold and inverted roof constructions. The outlets are suitable for connection to continuous waterproofing systems including single ply membranes, high-performance built-up felt, mastic asphalt, hot melt and liquid-applied, allowing specifiers to maintain drainage consistency across a wide range of roofing applications.

Comprehensive Product Range
Harmer AV Vertical Roof Outlets are engineered with anti-vortex (AV) technology, and are designed to provide optimum hydraulic performance, even during periods of intense rainfall.

Compared to conventional gravity outlets, Harmer AV Outlets can drain up to 40% more roof area, while increasing flow performance as the head of water at the outlet rises. This can help designers optimise outlet layouts without compromising drainage performance.

Manufactured from precision cast LM6 aluminium silicon alloy, the outlets are lightweight, corrosion resistant and fully recyclable. Aluminium offers an expected service life of up to 40 years in rural and suburban environments, and up to 25 years in industrial or marine locations.

Standard outlet bodies are supplied in mill finish aluminium, with polyester powder coated grates and clamping collars.

The range offers a choice of spigot and screw outlet configurations, allowing designers to select the most appropriate connection method for each project. Spigoted outlets are most commonly used, where the slab depth allows. For applications where there is a deeper build up and no joints, extended spigots can be specified.

Screw outlets are also suited to extended systems, but offer the flexibility of purchasing the outlets and threaded adaptors separately. Unlike the spigot or extended spigot option, screw outlets result in an additional joint in the system and take slightly longer to install.

Alongside the standard AV Outlets, the wider aluminium range includes specialist products designed to address more challenging detailing situations. Detail Outlets are available with 45° and 90° discharge options, together with two-way outlets for parapet applications, balcony outlets, gulley outlets for narrow drainage channels, and car park outlets for parking decks carrying cars and light commercial vehicles. Integral sump design, membrane clamping arrangements and unrestricted water flow all contribute to reliable long-term drainage performance across these more complex applications.

For the upgrade of existing drainage systems, Harmer AV Retro-Gulley Outlets offer a practical solution. Designed to fit within the original outlet and pipework, they eliminate the need to remove the existing rainwater outlet, reducing disruption and also providing a cost-effective approach to warm roof refurbishment projects. Developed in conjunction with the Flat Roofing Alliance, Retro-Gulley Outlets accommodate a range of existing pipe materials and internal diameters, making them suitable for many refurbishment scenarios.

Grate options are also available to suit the intended roof use. Domical grates are supplied as standard for general roof drainage, while flat grates are recommended for pedestrianised areas or beneath raised paving systems. Terrace grates, used with extension pieces, enable straightforward installation within paved roof terraces while allowing adjustment to align with surrounding paving before final fixing.

Supporting Fire-Safe High-Rise Construction
The Harmer Aluminium Roof Outlet range also supports modern high-rise construction. An aluminium threaded spigot adaptor option provides an A1 fire-rated connection between threaded aluminium roof outlets and a wide variety of Alumasc aluminium downpipes and other systems. This creates a fully compatible non-combustible drainage solution, compliant with current fire safety requirements for high-rise construction, and also eliminates the need for mechanical joints within the concrete slab.

Harmer Roof Outlets and Alumasc aluminium downpipes are both BBA approved powder coated, making the system A2-s1, d0 fire-rated. Products are A1 fire-rated if not painted.

Bespoke Product Options
Where standard products do not meet project requirements, Harmer also offers bespoke outlet configurations, including non-standard pipe arrangements and extended pipework, enabling designers to accommodate complex roof geometries or unusual drainage layouts without compromising system performance.

By combining high-capacity performance with one of the most comprehensive selections of aluminium roof outlet configurations available, the Harmer range provides architects, specifiers and contractors with drainage solutions capable of addressing virtually every flat roof application.

Architects, specifiers and engineers can quantify surface water using the unique AWMS Drainage Calculator

Harmer Building Drainage sits under the AWMS umbrella as one of five brands well known for innovation, quality and longevity. The four accompanying brands are Alumasc Rainwater Gutters & Downpipes; Skyline Architectural Aluminium; Wade Building Drainage and Gatic Civil Drainage & Access Covers.

Download the Harmer Roof Outlet Brochure here

For more information call 01536 383810 or visit www.alumascwms.co.uk