Do Nuralite Flat Roofs Need Ventilation?

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Posted 4 Jul 2016 15:00

Specifiers often ask Nuralite about roof ventilation. More recently, Architect Pip Cheshire asked about a “near flat” roof and if he used a Nuralite product whether it would need ventilation.

So, do Nuralite Flat Roofs Need Ventilation?

Short Answer: The short answer is…No.

No ventilation is required for the Nuraply 3PM membrane itself. The Nuraply 3PM system is a tough, reinforced, double layer waterproofing membrane system that is not affected by moisture.

In particular, a Nuratherm Warm Roof will be the ultimate protection from roofing moisture concerns – there will be none! Read below for “The Ultimate Solution”.

Longer Answer: However! As we all know, people showering, cooking and living in a building create moisture. This moisture combined with the warm air, rises and accumulates in the ceiling space, which will then condensate upon contact with the cold temperature found on the underside of the roof cladding. This can be detrimental to any roof structure within the cavity.

This means that buildings using the Nuraply 3PM flat roof system might still need ventilation in the roof.

Solutions to this moisture-laden air in the roof are “mushroom” type Nuravents in the roof surface itself or if possible, cross-flow ventilation through the roof structure and out through sofits.

Even so, venting the roof space can have its drawbacks, as there are situations where moisture can enter the building. In certain conditions humidity can enter the roof structure through the vents. The penetration of the membrane by these vents is also a potential weak point. 

The Ultimate Solution

Nuralite provides you with an ultimate waterproof and insulation solution to your flat-roofing needs, with its Nuratherm Warm Roof. This system completely negates the instance of interstitial condensation and therefore no ventilation is needed.

In the Nuratherm Warm Roof, insulation sits on top of the roof structure but below the roof membrane so that warm moist air inside doesn’t meet with the cold outside air. See the image above to see what Nuralite’s Nuratherm Warm Roof system looks like. For more information see Nuratherm Warm Roof Solution.


The Nuraply 3PM double layer membrane is not affected by moisture. However, alone it does not provide a solution to moisture in the roof cavity created by people inhabiting the building. To combat this other Nuralite solutions are recommended. The ultimate solution, Nuralite’s Nuratherm Warm Roof system includes insulation below the roof membrane that deals with any condensation as well as insulating the roof so that heat is contained.

Contact Nuralite to discuss your flat roofing needs and any concerns you might have.


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