Single ply roofing and humidity considerations

Single ply roofing and humidity considerations

When designing and installing a new roof for your commercial property, there are a lot of different things to take into account. From the wind load to the fall radiant and aesthetic appeal, your roof has to tick a lot of boxes. Humidity levels are another key consideration for any flat roofing project. So what do you need to know about the humidity level in your property? what kind of installation and equipment adjustments will you need to make? Well, here at Enviroply Roofing, we specialize in flat roofing for a wide range of commercial properties and developments. As a result, we have produced this guide to single ply roofing and humidity considerations.


Why is humidity a problem?

So, first of all, why is high humidity a potential problem for your roof? Well, high humidity increases the risk of condensation occurring. Essentially, as the warm air rises, and meets the colder air at the top of the building, the water vapour in this air will reach it’s dew point, and turn back into a liquid. The more water vapour there is, the more potential condensation can occur. This can cause a number of issues, including:

  • rotting wooden timber joists and structural frames
  • mould build up
  • internal leaks
  • deterioration of fixings

Single ply roofing and humidity considerations

For single ply roofing, there are a number of things that can be done to lower the risk of condensation. For warm roofs and cold roofs the considerations are different, as each type of roof is built in a different way. But to begin, relative humidity calculations will be used to develop the roof, helping to determine the positioning and size of the vapour control layer, as well as any necessary adjustments.


Warm roof considerations

A warm roof is designed with the insulation over the top of the roof deck, on top of a vapour control layer, and underneath the roof covering. So, to tackle any humidity and to prevent condensation, you should:

  • fill any gaps in the insulation to prevent cold air bridging
  • avoid air movement through the roof system, preventing cold air from travelling
  • use an appropriate vapour control layer, and install this correctly

Cold roof considerations

A cold roof is designed with the insulation between the rafters, so its important that the air can circulate, to reduce any humidity issues. This means you should:

  • leave a minimum 50 mm gap between the top of the insulation and the underside of the roof deck
  • install adequate ventilation at each end of the roof

Adjustments for high humidity environments

For high humidity environments, these considerations will not be enough. For swimming pools, sports halls, large commercial kitchens, and other areas with obvious high humidity, you will need to take additional measures. And this also includes buildings like schools and community halls, that may be heated intermittently, but then closed and unused for a long period of time. So, what kind of adjustments will need to be made for single ply roofing in high humidity environments? Well, there are several, including:

  • High performance metal lined vapour control layer to increase the water vapour resistance
  • Using a fully adhered single ply installation method instead of a mechanically fastened system. This is because the mechanical fastenings can rust in high humidity.
  • Changing carbon fixings to stainless steel fixings
  • Inclusion of air conditioning/ventilation to change the humidity inside the build

British Standards and humidity

In accordance with BS 5250 Code of Practice for control of condensation in buildings (Table D7), the correct equipment and materials can be installed to perfectly match the level of humidity in your environment.

This British Standards document provides detailed information for manufacturers, as well as recommendations and guidance for avoiding problems related to high moisture levels within buildings.

For more information or advice about single ply roofing for your high humidity environment, get in touch with the team today, here at Enviroply Roofing.