January 2019

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Wind Uplift FAQS ON WIND UPLIFT The experts at A. Proctor Group answer some of the frequently asked questions on issues around wind uplift. What is ‘wind uplift’? Wind uplift is a force that is applied to roofs due to wind pressure. Roofs should be designed to resist this force. Why is it important? Roofing underlays play a part in this resistance and will share the loads applied by the wind with the primary covering (tiles, slates etc.). These pressures can create a suction effect on the roof that can cause a ballooning of the underlay which, under extreme cases, can lead to slates / tiles being dislodged. This is an issue to the longterm durability of the roof, to health and safety of passers-by, with potential risks increasing during extreme weather and if lighter weight underlays are used. The detailing debate: overlaps? battens? tape? While British Standard BS 5534:2014+A2:2018 provides guidance on slating and tiling, there are still different viewpoints on correct detailing of roof membranes in order to mitigate the effects of wind uplift. BS 5534 states: Underlay laps should be covered by a batten and, where necessary, the lap of the underlay adjusted to coincide with the nearest slating or tiling batten. When tile battens are used, it is accepted practice to lay out the membrane so the laps fall below a batten. If the tile gauge does not allow this, then either the lap can be increased to ensure it is below a batten or an additional batten (sometimes called a “fly batten”) should be installed to cover the lap. Many roofers consider additional battens trip hazards and opt to increase the depth of the lap instead, despite the increase in membrane material costs this results in. BS5534 offers further guidance stating: Laps may also be sealed using proprietary means in accordance with manufacturers’ instructions. Above: Roofshield from A. Proctor Group. While the industry waits for more comprehensive Sealing roofing underlay laps is most often done research and evidence to inform an expected with tape which can have a number of future addition to the Standard regarding drawbacks. On top of the potentially timeconsuming process of taping every lap, tapes shielding factors for air permeable membranes, contractors can look to industry accepted must first be tested for efficacy and approved for proprietary testing and third-party evaluation for use with the specific roofing membrane. Tapes reassurance. require clean, dirt-free surfaces and ideal weather conditions to ensure a proper seal, factors that are never guaranteed on a building site. Sealing laps where the underlay is unsupported also adds difficulties in ensuring effective sealing notwithstanding safety considerations. As previously mentioned, Roofshield exceeds the Standard’s required performance values for air and vapour permeable membranes, and is a robust 3-layer spunbonded material with the highest water resistance class possible for a membrane of its type (W1). Roofshield: the benefits of In addition, Roofshield’s two BBA air permeability certificates state that, when In February 2018, a second installed on appropriately spaced amendment to BS 5534 British battens, the membrane will Standard for Slating and Tiling was adequately resist wind loads published with two key additions imposed on the underlay and regarding air permeable underlays. reduce the wind uplift forces Above: Roofshield is suitable for use in The first change occurred in the all of the UK’s wind zones fully acting on the external roof definitions of roofing underlay types. Previously, underlays were supported or draped between rafters, following published batten guidance. covering. Roofshield is suitable for use in all of the UK’s wind defined according to their water vapour resistance alone (HR vs. LR membranes). The addendum added a new definition for membranes with physical properties that combine low water zones fully supported or draped between rafters, following published batten guidance and does not require the laps to be taped in UK Wind Zones 1, 2 or 3. vapour resistance with high air permeability, Still have questions about wind uplift or detailing along with specific values membranes must Roofshield? Contact the A. Proctor Group for achieve to be defined as such. Roofshield further assistance. exceeds the definition’s performance values for both air and vapour permeability. Contact A. Proctor Group The second addition was an updated shielding 01250 872 261 factor for air permeable underlays related to the www.proctorgroup.com fixings at roof hips and ridges. @proctorgroup 22 TC JANUARY <strong>2019</strong>
HIGH PERFORMANCE LIQUID WATERPROOFING SYSTEM BENEFITS & PRODUCT INFORMATION BBA certified for life in excess of 25 years. NHBC and Green Roof Approval. ULTRAFLEX can be used on new or existing roofs, walkways, balconies, gutters etc. Ready to use straight out of the tin, application with solvent resistant roller. Use fully reinforced with ULTRAFLEX matting ensures easy ‘wet on wet’ application. Can be used all year round – moisture curing. Fully trafficable when cured. Instantly rain resistant after application. Once installed, forms a seamless membrane. Exellent adhesion to different substrates: plywood, bitumen membranes, asphalt, metals, brick, concrete, wood etc. Fresh concrete must be cured for 28 days. On EPDM and TPO it is recommended to install patch test to check compatibility. Do not use silicone sealants. Always use PU based mastics.
Page 1 and 2: DT435 el Single arbon Self Stitcher
Page 3 and 4: I V Editor’s Comment MATT DOWNS E
Page 5 and 6: REGULARS 18 NFRC TECH TALK Bob Rich
Page 7 and 8: HIGH PERFORMANCE WATERPROOFING 6 33
Page 9 and 10: THE BEST ALL ALUMINIUM LANTERN ROOF
Page 11 and 12: Handrails:- EasyGuard free-standing
Page 13 and 14: A P O S I T I V E P A R T N E R S H
Page 15 and 16: Complete Building Envelope Solution
Page 17 and 18: THE FUTURE’S BRIG HT FOR ANY BUIL
Page 19 and 20: Innovative upgrade & refurbishment
Page 21: Come rain or shine, our rooflights
Page 25 and 26: Heavens above: Storing insulation l
Page 27 and 28: looked at pitched roofing standards
Page 29 and 30: Richard Bishop, Category Manager fo
Page 31 and 32: octor the A Proctor Group Collectio
Page 33 and 34: should make up at least one-third o
Page 35 and 36: Expertise... through teamwork When
Page 37 and 38: CALL FOR ENTRIES Submissions are no
Page 40 and 41: Bonding to Roof Decks BEST PRACTICE
Page 42 and 43: Single Ply Roofs INSTALLING A SINGL
Page 44 and 45: Rooflights LET THERE BE LIGHT: KEY
Page 46 and 47: Project Focus: Rooflights NDC STEPS
Page 48 and 49: Lone Workers LONE WORKING: STEPS TO
Page 50 and 51: Lone Workers Risk The purpose of a
Page 52 and 53: EPDM Lake Project AN INTERESTING US
Page 54 and 55: Roofing Updates For further info on
Page 56 and 57: Facade Inspections IT’S TIME TO W
Page 58 and 59: Cladding Updates For further info o
Page 60 and 61: Insulation & Fabric First VENTILATI
Page 62 and 63: Company Focus: IKO INVESTING FOR A
Page 64 and 65: Business Talk PROTECTING YOUR BUSIN
Page 66 and 67: The Apex HANDLING “DIFFICULT” C
Page 68: METAL RAINWATER & ROOFLINE PRODUCTS

January 2019

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