The Red Zinc Clad House at Blunham, Bedfordshire case study features a hidden eaves box gutter detail in the standing seam zinc roofing. In this article SIG Design & Technology look at hidden box gutters, when you would use them and what to bear in mind.
When to use a hidden eaves box gutter
Hidden box gutters are concealed behind the edge of the roof, rather than attached to the eaves. This has the advantage of making it possible to have a crisp eaves detail, which can either be shallow or sharp, or flush with the edge of the building as with the house in Blunham, where the standing seam zinc cladding appears to travel up the wall and over the roof in one smooth, and apparently seamless surface.
A hidden eaves box gutter isn’t necessarily the most cost-effective way of taking water off a pitched roof. As well as additional work by your skilled metal roof installer, the structure underneath has to be right, supporting the gutter whilst allowing the roof trusses to do their job. Some solutions will therefore require additional structure to support the gutter and the eaves.
What to consider when designing a hidden eaves box gutter
1. Calculate the size of the gutter according to the size of the roof and the water it will need to carry, in accordance with the British Standard guidance BS EN 12056-3: 2000.
2. Make sure the gutter size is large enough to enable your installer to get his tools inside it. If an architect has specified a gutter that is only 44mm wide, it will not only be too small for the rainwater runoff, but also impossible to fit.
3. Confirm the structure to both support the box gutter and the roof, and to incorporate the space it takes up in the roof.
4. Ensure that the front edge of the gutter is a minimum 10mm lower than the rear to allow any overflow to evacuate outside the building. Whilst your box gutter may discharge outside the building, the gutter itself will be within the building footprint and if for any reason it overflows, you’ll want the excess water to evacuate off the end of the roof, not back into the building.
SIG Zinc & Copper provide a free specification service, free detailing and support for your metals project.
Hidden eaves box gutter details
elZinc have published three ventilated hidden eaves box gutter details:
• DLSS-3.4.01 Hidden Eaves Box Gutter (over zinc angle seam cladding)
• DLSS-3.4.02 Hidden Eaves Box Gutter (over zinc fascia)
• DLSS-3.4.04 Hidden Eaves Box Gutter (drip edge apron over stone cornice)
These are just some of the comprehensive set of 550 architectural details for zinc roofing and cladding you can now download from their website.
Zinc roofing and cladding details are available:
1. Shown over two different substrates, for example softwood board and OSB/plywood. Some composite boards have adhesives which may be corrosive to zinc, so which board you use will affect the detail and the build-up;
2. In PDF and DWG format, with a plot styles file to ensure correct detail reproduction;
3. With notes showing the limits of application and alternatives, and
4. With links to similar details to assist in detail choices
You can also view some of the details in interactive 3D format.