Getting it right - Warm, Green and Stone Ballast RoofsJohn Stallard

Published 29th May 2017

Green roofs are often chosen by clients who want their home to blend into its surrounds, whether that be a rural setting amidst an undulating landscape, or a coastal location set within native grasses.

The primary function of a green roof is to provide a setting for vegetational planting, but with that comes numerous requirements for its success, including the right components, and the roof system’s ability to retain moisture in the soil, and drain appropriately.

Ballast roofs on the other hand, involve less technical complexity but can achieve a similar natural aesthetic.

Waterproofing Systems NZ’s John Stallard says while the technology for warm and green roofs is not new, the sector is advancing and combinations of warm, green and ballast roofs are becoming more common as people come round to the idea and each of these systems’ benefits.

Warm roofing systems provide the thermal basis for both stone ballast and green roofs.

"Our warm roof system has the insulation installed above the structure with the waterproofing membrane installed directly over the insulation. It’s designed to keep hot or cold climatic conditions isolated, while the insulation system ensures ambient temperatures are maintained within the building," John says. "The addition of a green or stone ballast roof adds to the warm roof system’s effectiveness.

"Waterproofing Systems’ stone ballast system is less technical than a green roof, but represents a very good looking and less bulky roof finish, which is very effective when combined with a warm roof."

In order to create a stone ballast roof that will not allow airborne fines (dust, sand etc) to get into the drainage system the filter cloth inclusion is very important. "The anti-root membrane ensures the stone ballast system is protected from any small weeds or plants to ensure water tightness is maintained throughout its lifetime.

The two-lawyer bituFLAME anti-root membrane system consists of a bituFLAME 3mm sand base sheet and a 4mm anti-root capsheet. bituFLAME anti-root has preventative B2 incorporated into the bitumen which gives a high resistance to both root penetration and aggressive attack from chemical fertilisers, if a green roof is utilised above the system.

"If a green roof system is specified in conjunction with the warm roof, it provides a stunning visual experience, whether that be to blend into paddocks in a rural setting, to provide a coastal finish, or to create a vegetable roof garden. Once it’s completed, the anti-root system protects the membrane and insulation from being penetrated and from weathering, while simultaneously ensuring a high level of insulation and a lower need for artificial heating and cooling within the home."

To ensure a green or stone ballast roof performs to the highest standards and is effective over time, it’s important to understand the benefits of each component and how those can be utilised in the best way.

If you’re considering a stone ballast or green roof, get in touch with Waterproofing Systems NZ here to find out what’s best suited to your project.