Need to protect waterproofing

Despite the danger of birds dropping loose stone from roof tops, Architects and Builders continue to use loose stone for rooftops. There is a very good reason for this. 

All flat top building roofs must be built with very sound drainage and waterproofing. The problem Waterproofing is a synthetic polymer and highly susceptible to UV damage, particularly given flat roofs are  exposed to direct sunlight for up to 12hours a day.  

To protect this waterproofing, a stone or paving product must be used to shade the waterproofing and take the full brunt of the Sun’s UV. 

Why must rooftops use large stone?

A cement slab can not be poured, because the waterproofing and drains must to be accessible for any future repair works. 

Segmental style pavers like terracotta pavers could be used, but compared to concrete this is an expensive option. There is a lot of fabrication cost in fabricating the pavers to shape and colour that makes them look nice for walkways etc. But this is not necessary on a roof where people are’t allowed to access. Therefore, raw, untreated stone is the best choice. Using a common ubiquitous stone, it is cheap to quarry and requires no processing costs unlike cement or pavers. 

Larger, 20mm type stone is often specified for rooftops because it is cheaper than smaller stone. Because larger type stone is not suitable for use on paths or driveways, it sees much less demand in the building industry. Low cost, large stone is therefore ideal for rooftops that dont allow access, with little to no foot and vehicle traffic.

Does Gravel Binding resin lasts longer than netting?

Yes. The whole reason the stone is there on the rooftop is to protect a man made, polyester product from the Sun’s destructive UV rays. Bird netting is a good product in its effectiveness preventing birds dropping stone and its relatively low up front cost. However, polyethylene netting under tension gets damaged by the sun – even when it is UV stabilised. 

After evenly pouring on the binding resin over loose stone, the polyurethane coasts the stone and locks it into place. The stone is glued from below at the multiple touch points between the stone, forming a strong, multiple crossed-linked binding matrix. For ballast style(*) stone rooftops, PourOn polyurethane resin will prevent birds removing stone for more than 10 years, because the resin binding the stone is not exposed to the sun! 

Is rooftop netting a ‘cheap fix’ over binding the loose stone?

Not exactly. While it’s possible for netting to last a 10 year warranty period, there is no question even ‘UV stabilised’ polyethylene weakens progressively over time. This is where we ask you question the real limitations of a 10+ year warranty on a polyester product permanently exposed to the wind, rain and sun.

Netting may be still present in 5 years time, but what will it look like? Will it require maintenance and patching? Does the warranty cover freak storms and wild winds on weakened netting? 

By contrast, using PourOn gravel binding resin, It is only the raw, natural stone exposed that is left exposed to the harsh UV.

The resin is not affected by wild winds and completely inert to rainwater (Our resin is even used in permanently summarised chlorinated pool water).

When you consider the detail, this makes sense to bind the stone (rather than net it). However the reality is most builders are more familiar with pest control netting, especially in an emergency like birds dropping 20mm pebble from 5 stories up!)

It is far more beneficial when building managers and strata committees have the time to research all options and understand the long term and aesthetic benefits of binding the stone, rather than opting for a relatively inferior solution to a very dangerous and costly problem.