Simple, clever sustainability – Part 4: Best practice in designing metal roofing systems with piping penetrations

by Darren
Simple clever sustainability part4

It is often necessary to mount equipment on top of a roof. Safintra gives advice on how to cope with piping penetrations through concealed-fix and standing seam roofing profiles.

This article is part of a series on metal roofing and cladding systems that promote sustainability.

Source: Extracted from Rob Haddock’s article entitled “Metal roofing from A (aluminium) to Z (zinc)”.

Whether dealing with concealed-fix or standing seam roofing profiles, piping penetrations through the profile cause challenges and potential headache.

The launch of the Newlok standing-seam metal roofing system into the South African market represents state-of-the-art metal roofing. The profile is a durable, sustainable and eco-friendly alternative that provides three or four decades of reliable service life.

Unfortunately, the relative maintenance freedom which it offers if installed correctly, is often sabotaged when essential rooftop equipment and ancillary mechanicals are mounted on top of the roof.

The sure way to prevent roofing problems is to ensure that the rooftop doesn’t have anything on it. But this isn’t quite realistic – in fact, it is often necessary to mount HVAC equipment, screens, piping and more. However, with some basic understanding of the do’s and don’ts, it can be relatively trouble-free.

HVAC and above-roof units
In the case of installing an HVAC system, even though the unit can be mounted on a structure above the roof, the roof membrane will still be penetrated with piping. The challenge is to waterproof the holes while maintaining the natural thermal cycling integrity of the roof.

Such a roof mounting can be successfully achieved by using special seam-clamping components such as S-5 clamps from Safintra, which grip the seam of the roof panel without puncturing the membrane. These clamps are compatible with aluminium-zinc coated roofing materials and will not violate warranties.

Round piping penetrations
When installing penetration pipe flashings, Safintra recommends that ethylene propylene diene monomer (EPDM) rubber or silicone flashings such as the DEKS range should be used to prevent water ingress, as it can withstand extreme temperature fluctuations.

Flashings are available in a variety of colours, although black has the greatest ultraviolet (UV) resistance and therefore the longest lifespan.

Best practice installation involves using a stainless steel draw band at the top of the flashing to further secure it and ensure that the flashing never inverts itself. This will add about five years of life to the assembly. It should then be secured onto the metal panel using fasteners and butyl.

Excess butyl tape should be trimmed away and a bead of one-part polyurethane sealant should be filleted around the joint created (base to roof). This bead will hide and protect the butyl from direct exposure to sunlight, ensuring a longer life. After a significant service life, this assembly is easily replaced.

When attaching the pipe flashing, it must be anchored to the roof panel only – not into the building, structure or deck. Doing so would create an inadvertent pinning of the roof panel, violating its freedom of thermal movement.

Ideally, these flashings should be centrally located on the roof panel so that there is free drainage to both sides with no interruption of the seams. If the location of the pipe interrupts a seam and it cannot be relocated, then a preformed adapter plate can be fabricated to span both panels adjacent to the seam and the pipe flashed per the above to the adapter plate. Companies that pre-manufacture curbs will make such adapter plates on request.

In short
When installing pipe flashing, remember:
•    Use EPDM rubber pipe flashings (black).
•    When possible, locate pipe flashing centrally in the panel.
•    Use stainless steel draw band.
•    Butyl tape beneath base, then fillet with one-part polyurethane.
•    Do not pin to structure or deck.

Rooftop mountings and penetrations are a challenge for any roof type or material. Following these simple guidelines will ensure trouble-free and enduring performance for a state-of-the-art, low-slope metal-roof system.

Safintra South Africa
Tel: 011 323 6300
Email: info@safintra.co.za
Website: www.safintra.co.za and www.safintra.com

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Branches in South Africa: Johannesburg, Durban, Cape Town, Nelspruit, Polokwane, Port Elizabeth and Bloemfontein.
Further operations: Namibia, Zambia, Mozambique, Malawi, Tanzania and East Africa.

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