![]() ![]() ![]() The methodologies for calculating these forces and specifying an appropriate outer covering are detailed in the BS5534:2014 +A2:2018 standard. Firstly, they provide a degree of resistance to wind uplift forces. ![]() These underlay membranes contribute to the performance of the roof systems in a variety of ways. ![]() It does not mean the specification of the outer covering can be reduced, or that slates/tiles can be used below their minimum recommended pitch. “Secondary” protection in this context means temporary protection during the construction phase, and in case of in-service damage to the primary covering. There are two main types of moisture that roofs of all types must control, moisture from *internal* sources, vapour and condensation, and moisture from *external* sources, rain and snow.Įxternal moisture is assumed to be primarily deal with by the external weatherproofing once the building is complete, but in order to provide a secondary layer of weather protection, roofs are fitted with an underlay membrane beneath this outer layer. The performance of a pitched roof in relation to heat flows, moisture transfer and air leakage are closely linked, and a having good understanding of the principles outlined in BS5250:2021 as well the relevant regulations is important. In northern Ireland, this is Technical Booklet F, and in the Republic of Ireland, Technical Guidance Document L.įor projects where the aim is to exceed the regulation energy performance standards, it's also worth considering the recommendation given in the Passive House standard, even if passive house certification is not a project requirement. The energy performance aspects of roofing systems are covered in England & Wales by Approved Document L, in Scotland by Section 6 of the technical standards. This means that, unlike for example energy performance, moisture control practice in roofing is relatively similar across all four sets of regulations. Approved Document C in England and Wales, covering “site preparation and resistance to contaminants and moisture”, The Scottish “Section 3: Environment”, Northern Irish Technical Booklet C and Technical Guidance Document F in the Republic of Ireland all reference this guidance. The building regulations across the UK and Ireland all base their moisture control guidance for roofing on BS5250. This change helps facilitate a more holistic approach to the management of moisture, air leakage and energy performance. The BS5250 standard was formerly the "code of practice for the control of condensation", but now in its 2021 edition covers the wider remit of “management of moisture” including the effects of a wider variety of moisture sources on building design. We’ll then look at the physics and design influences in more detail and how roofing practice is adapting to meet the changing nature of these challenges.īS5250 The starting point for a successful roof design must be keeping the building dry, and the relevant guidance can be found in the BS5250:2021 Standard. We’ll start out with a look at BS5250:2021, the code of practice for moisture management, how it relates to roof design and the building regulation, and some of the roof types it introduces. Today we’re running our third RIBA-assessed webinar, this time looking at pitched roofing design and what strategies we can adopt to manage the movement of air and moisture to ensure our roofs are both energy efficient and free from condensation. Our series of webinars has been running now since 2020, and if you’ve missed any you can go back and review them all on-demand right here on our YouTube channel. Good morning everyone, my name is Keira Proctor, and welcome to our twelfth webinar of 2022. ![]()
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