Scarecrows on the Roof?

February 13 2019 0comment

Scarecrows on the Roof?

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In inverted roof is also known as a “protected membrane” or “upside down roof” because the waterproofing layer of this type of flat roof is beneath the thermal insulation, rather than above it.  The waterproofing layer will usually be a liquid-applied membrane above a concrete roof slab and has insulation boards laid over it, which is weighted down with a layer of ballast, often gravel or pebbles.  Any rainwater falling on the roof will trickled down through to the membrane layer where it should drain away through rainwater outlets. 

One of the major benefits of this type of roofing method is that the membrane is protected from expansion and contraction caused by temperature fluctuations (such as frost, solar radiation, etc.).  the membrane is also protected from damage caused by workers who need to access the roof for maintenance purposes, so this method is becoming increasingly popular. 

However, some premises featuring this type of roof have come under attack from the skies – gulls, crows and other large birds have been mistaking the ballast (whether pebble or gravel) for food and picking it up in their beaks.  This is common practice for such birds, especially gulls which have long been in the habit of picking up shells and then dropping them from a height in order to smash them open and eat the delicious sea creatures they find inside.  The birds even have a “favourite” size of ballast, with most of the pebbles dropped by the birds measuring between 20mm and 75mm (the larger size probably being dropped by avian culprits whose “eyes are bigger than their bellies”). 

When the birds perform similar “shell-cracking” manoeuvres using ballast material, life in the vicinity can get pretty dangerous, with pebbles raining down from above.  Glass roofs get smashed, windscreens are broken, the bodywork of cars get dented and PVC panelling gets cracked.  Worse still, there have been plenty of near-misses reported by people on foot going about their daily business!

Falling pebble ballast is fast becoming one of the hazards of modern life.  Pebbles dropping from the sky represents an obvious health and safety risk to the general public and all who use the buildings and surrounding areas.  This means that solutions must be found and we’re not advocating installing scarecrows on every flat roof!

One solution is the installation of pavers but this comes with an increased cost.  Increasing the size of the ballast is also an acceptable solution, as does decreasing the size of the pebbles used to lessen their destructive power. 

The most effective method for deterring birds from trying to gobble up the ballast on flat roofs around the world is to employ a ballast netting system which will prevent the birds from accessing the delicious looking pebbles.  This is a simple, yet cost-efficient solution as it needs no mechanical fixings, can be installed retroactively and does not pose a risk to the roof warranty.  For roofing contractors, this is a great add-on to the package you offer which won’t involved training in new techniques or methods, it’s just an added extra to offer your clients in future.

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