Wind uplift resistance: how standards compare across the UK and Ireland

At Glidevale Protect, we supply roofing and construction membrane products to projects across the UK and the Republic of Ireland, so our team is well versed in the nuanced differences and regional variations in the regulatory guidance. It’s crucial for contractors to be able to trust that all products specified are compliant as well as being fit for purpose to ensure they’ll perform as intended, especially as the focus on long-term building performance continues to grow. As regulations become more complex, contractors are rightly demanding more clarity from supply chain partners like ourselves.

This commitment to clarity and technical transparency underpins our entire approach as a manufacturer and supply chain partner. We recognise that specifiers and contractors need confidence that the pitched roofing membrane products they select are suitable for their project’s geographical location as well as being compliant with the regional standards that apply. This is particularly important in areas exposed to more severe weather conditions, where the performance of membranes and associated components plays a critical role in the resilience of the building envelope as a second line of defence after the roof covering. However, there are some differences between the Republic of Ireland’s code of practice and UK standards which could potentially cause confusion and thus a homogeneous approach to specification should be avoided.

Understanding the relationship between S.R. 82 and BS 5534

S.R. 82:2017 is Ireland’s Slating and Tiling Code of Practice and BS 5534 is the standard used in the UK to provide guidelines for the installation of slating and tiling on pitched roofs. Both documents share the same core objective of ensuring safe, durable and well installed pitched roofing systems. However, there are subtle but important differences between the two standards, particularly in the way wind uplift resistance is assessed in relation to pitched roofing membranes.

One of the most significant differences is how the wind zones are classified in Ireland. Rather than categorising a membrane’s resistance to wind uplift by zones 1-5, where a zone 5 compliant underlay can be used across the whole of the UK, S.R. 82 segments the Ireland into two zones, one classed as moderate exposure to wind driven rain and the other as severe exposure. This is based on the levels of the driving rain index and wind speeds in the appropriate areas of the country. In districts where there are buildings which stand above their surroundings or buildings of any height on hill slopes or hill tops, these should be regarded as areas with severe exposure. Both moderate and severe exposure zones require a minimum design wind pressure in pascals that the pitched roofing membrane needs to achieve in order to be suitable for use. To put this into context in comparison to UK standards, the moderate exposure zone requires an underlay to have a minimum design wind pressure of 1150 N/m² using a 250mm batten gauge, whilst severe exposure requires 1330 N/m² of wind pressure to be handled by the underlay, again at 250mm batten gauge. In the UK, 1150 N/m² is the minimum pressure that is required for a compliant underlay at 345mm batten gauge, meaning it can be used in wind zones 1-3 in mainland UK, whereas an underlay with a minimum of 1330 N/m² pressure can be used in wind zones 1-4, again at 345mm batten gauge.

It’s the maximum batten gauge that matters

One fundamental difference between S.R. 82 and BS 5534 relates to the batten gauge referenced in the standards that underlays need to meet to be deemed satisfactory for use. S.R. 82 references a 250mm batten gauge as part of its code of practice, whereas BS 5534, by contrast, uses the maximum design gauge of 345mm. This wider spacing places greater stress on the underlay during testing than at 250mm and therefore provides a more demanding measure of wind uplift resistance. However, even though S.R. 82 references 250mm batten gauge, this is contrasted with other detail stipulated in the standard that states underlays should have the adequate resistance and stiffness against wind uplift loads with battens set at the maximum design gauge, to avoid contact with the underside of slates or tiles and to prevent the load of wind uplift being transmitted to the surface of the roof. This is a key point which means that designers in Ireland should be ensuring that the specified roofing underlay is shown to be adequate for use whether in moderate or severe exposure areas at the worst-case scenario of 345mm batten gauge. These performance characteristics should be able to be evidenced by the membrane supplier through independent, third-party certification.

These differences do not make S.R. 82 a weaker standard. Rather, it highlights the importance of understanding the detail behind performance claims. A product that achieves a high resistance to wind uplift at 250mm batten gauge will achieve a lower pascal rating with wider spacing between battens at 345mm. For Ireland, where all wind uplift zones fall into either moderate or severe exposure, this distinction matters.

The importance of the batten gauge in practice

As S.R. 82 uses a 250mm batten gauge as part of the standard, some suppliers may present wind uplift results that appear suitable for Irish conditions but are not based on the worst-case test scenario. For example, a membrane might achieve a resistance for suitability in a moderate exposure area at 250mm batten gauge yet not meet the minimum of moderate exposure when tested at 345mm, which means the product is not suitable for installation across the Republic of Ireland. If a roofing contractor assumes that a membrane with a claimed wind uplift resistance value at 250mm batten gauge reflects real world performance, they may inadvertently install a membrane at 345mm that is then ultimately not suitable for the exposure level of the site.

This is all particularly relevant because a high number of pitched roof installations in Ireland are set at a 345mm batten gauge in practice. This means that the referencing of 250mm batten gauge in S.R. 82 with regards to wind uplift resistance of roofing underlays can cause confusion and a mismatch during specification between the requirements detailed within the standard and the conditions under which the roofing underlay is ultimately installed.

We can provide a range of roofing underlays, type LR (low resistance to vapour) that have been independently tested for wind uplift resistance and meet the requirements of either moderate exposure or both moderate and severe wind exposure areas in Ireland, including our Protect VP300, Protect VP400 Plus LR and Protect Zytec ranges. In all cases, our technical data sheets show a clear rating for the worst-case scenario – wind uplift at 345mm batten gauge to denote suitability and our independent third-party certification schedules break down the performance of the membrane at different batten gauges. We also have an air and vapour permeable membrane – Protect Viking Air and a range of type HR – vapour impermeable and airtight membranes that can also be used across Ireland with technical data to evidence suitability in both exposure areas.

Avoiding a race to the bottom

We have seen examples in the market where lower quality membranes are being used on Irish projects and are seen as compliant with the minimum levels of wind uplift resistance requirements at 250mm batten gauge as detailed in S.R. 82. While these products may technically comply with the standard, they may not provide the level of performance needed when a wider batten gauge may be installed on site and thus will not meet the requirements for the specific wind exposure conditions of the location.

This creates a risk for contractors, specifiers and building owners. If a membrane fails to provide adequate wind uplift resistance, the consequences can include water ingress, damage to the roof covering and potential building safety issues. It also raises questions around warranty validity and compliance with the Building Control Acts, which require the use of proper materials. It is therefore always prudent to confirm a membrane’s pascal resistance to wind uplift at the worst-case scenario!

The intention of S.R. 82 is to provide a clear and robust framework for roofing practice in Ireland. The challenge arises when membrane suppliers present performance data without full context and transparency and this is why integrity in this matter is so important.

The importance of clear technical information

However, developing products that meet the necessary standards is only part of the process. Ensuring that the supporting technical information is accessible and easy to understand is equally important. Clear technical information also helps bridge the performance gap between design and operation by ensuring buildings perform as intended and that the products used on site are appropriate for the conditions they will face. When technical information is clear, complete and independently verified, it supports informed decision making and reduces the risk of misinterpretation.

We at Glidevale Protect remain totally committed to providing transparent technical information that supports our customers in making informed decisions. In a market where conditions are demanding and regulations are precise, we strongly believe that clarity is absolutely essential and helps strengthen trust across the supply chain.

Our Technical team can provide detailed guidance about wind uplift resistance. For more information call them on +44 (0)161 905 5700, or email technical@glidevaleprotect.com.

Or to request a CPD seminar on this topic tailored to either the UK or Ireland, visit www.glidevaleprotect.com/CPD

You may also be interested in…