ROOF SLOPE D E S I G N G U I D E D G R S

Transcription

1 ROOF SLOPE D E S I G N G U I D E DG RS

2 ROOF SLOPE GUIDE Selecting the optimum roofing profile for applications where is a key consideration. Incorporates detailed regional rainfall intensities. Important note The information contained within this brochure is as far as possible accurate at the date of publication, however, before application in a particular situation, Stramit Building Products recommends that you obtain qualified expert advice confirming the suitability of product(s) and information in question for the application proposed.while Stramit accepts its legal obligations, be aware however that to the extent permitted by law, Stramit disclaims all liability (including liability for negligence) for all loss and damage resulting from the use of the information provided in this brochure. 2

3 Roof factors The major factors when considering s are Economy Drainage Durability Wind resistance Safety Services Aesthetics This guide focuses particular attention on drainage and gives comprehensive information on the drainage characteristics of Stramit s range of roofing profiles.this, along with rainfall data for major locations, will enable easy selection of the best product for each application. Economy Roof can have a significant effect on the cost of a building. The extent of this effect is dependent on building size and proportions. Generally the longer the and the lower the building height the greater the cost reduction from minimising roof. These savings are in the wall structure and wall cladding. It should be realised however that increasing the sufficiently could reduce wind pressures and lower the roof structure cost. Drainage Design basis All /drainage capacities in this publication are based on rainfall intensity of a 100 year ARI (Average Recurrence Interval) of 5 minutes duration. The effective flow areas of roofing profiles are conservative. They are based on water being limited to the depth fully below each profile anti-capillary feature, and further reduced by a freeboard allowance. Recent tests at University of Technology, Sydney on several Stramit profiles have confirmed the adequacy of the data. Roof run length The length is the combined length of roofing run contributing to water flow in any one sheeting pan (or trough) at the lowest edge. If roof penetrations or spreaders are present it is likely that the maximum length will exceed the distance from the ridge to the eaves. Water flow is complex. However a simplified method of estimating water flow is generally satisfactory. The illustration shows a typical roof arrangement where two penetrations influence the length in various sheeting pans.although the nominal roof length is 30m, the Roof Run Length is 44m in this case ridge eave Curved roofs Spring-curved convex roofs can provide an excellent solution to roof drainage, particularly on large roofs. A convex curve approximates the increasing volume of water along the and therefore can lead to efficient structures. Information on spring-curving of Stramit profiles can be found in the publication Spring Curving Guide. Variable pitch roofs On very large roofs drainage can lead to increases in and consequent increases in structure cost. A practical method to reduce the structure in these cases is to vary the pitch down the roof. Taking advantage of occasional expansion joints, each segment of roof sheeting can be at the optimised. For each roof segment the maximum roof run length is only considered from the lowest point of that segment to the ridge. The effects of any roof penetrations must be accounted for TYPICAL VARIABLE PITCH ROOF 5 o 3 o 7 o 2 o 1 o 1 o (Note if practical place roof penetrations towards the top of a where water flow is less significant.) 3

4 Durability Durability is considered from the perspective of minimum fall and the benefit of additional fall. It is essential that the minimum fall of roof is maintained to ensure that water drains away. This minimum must be maintained over the entire roof, and throughout the life of the building. Water ponding on the roof will gather dirt and airborne particles. This compounds the problem by retaining moisture after most water has dried, and also soaking up condensation and dew. The ensuing prolonged exposure of a section of the roof to a damp chemical soup will reduce life expectancy. The minimum s set by Stramit for its profiles are based on two factors. These are sheeting stiffness (which resists permanent deflection) and the ability of a profile to be turned up or down at the sheet ends to prevent incursion of wind blown rain. The benefit of additional Further durability benefits can be gained from increasing. The major benefit comes from increased cleanliness. Increasing increases water velocity and assists gravity and wind in removing debris. A minimum of around 5 o is considered necessary to achieve these benefits. Safety Metal roof sheeting has a relatively smooth surface and, particularly in combination with oil from manufacture or surface water, can be slippery. Increasing the increases this risk. It is difficult to define a safe ; however, roofs with a of more than around 25 o require the use of ladders or walkways. Services Where services are to be installed on the roof it is generally more convenient to minimise the. This will make installation and maintenance easier, improve safety and may reduce the visual impact. Aesthetics For many buildings the roof forms a major visual component. Whether it be minimising to hide necessary rooftop services, or increasing the for overall visual balance, this guide will assist in selecting the correct product for the desired. THE EFFECTS OF DIFFERENT FACTORS ON ROOF SLOPE drainage durability wind resistance Wind Resistance Many factors influence wind pressure on a building, and on the roof in particular. These include site factors such as location, topography and exposure, as well as building geometry factors such as height, plan ratio and permeability. The of the roof is another factor. The influence of on wind pressures is interdependent on the building geometry factors.there is however a trend worth considering in building design. As wind uplift pressure is often the limiting criterion in roof sheet sizing and spacing, it can be worth minimising. This can only be achieved by increasing the to 10 o or more. At 20 o the pressure can actually halve. Further increases to 45 o have little effect, and beyond this pressures generally increase. Use AS when considering changes to roof to reduce wind pressure. economy safety services How to use 1. Calculate the maximum length. 2. Establish the rainfall intensity for the location of the building. These can be read from the table for many Australian locations, or use the maps for more specific locations within the surrounding areas of Sydney, Melbourne and Brisbane. 3. Using the Roof Slope table for the next highest rainfall intensity, select a roofing profile and to match the maximum length. 4. Check that the selected product is available for the building location using the Regional Product Availability chart. 4

5 Regional rainfall intensity Values of rainfall intensity in the table and maps have been derived from AS3500 Part 3 Stormwater drainage. It should however be emphasised that the extent and longevity of records in Australia are limited and any such data therefore carries with it a degree of uncertainty. SYDNEY REGION GOSFORD 220 RICHMOND RIVERSTONE HORNSBY ST. IVES PENRITH BLACKTOWN YEAR RAINFALL INTENSITIES (mm/hr) Australian Capital Territory Queensland Canberra 194 Brisbane 333 New South Wales Bundaberg 318 Albury 191 Cairns 38 Armidale 219 Charleville 23 Batemans Bay 279 Charters Towers 285 Bathurst 197 Cloncurry 228 Bowral 225 Goondiwindi 24 Broken Hill 181 Gympie 299 Coffs Harbour 293 Innisfail 323 Cowra 203 Longreach 251 Dubbo 221 Mackay 33 Forbes 209 Mt.Isa 223 Gosford 240 Noosa 320 Goulburn 197 Proserpine 35 Kempsey 283 Rockhampton 33 Lismore 278 Southport 308 Lithgow 191 Toowoomba 251 Maitland 224 Townsville 34 Mittagong 227 Warwick 240 Newcastle 233 Tasmania Nowra 280 Burnie 191 Orange 214 Hobart 155 Parramatta 230 Launceston 150 Penrith 220 Victoria Port Macquarie 290 Ballarat 184 Riverstone 218 Geelong 172 Sydney 273 Lakes Entrance 179 Wagga Wagga 190 Melbourne 18 Wollongong 294 Mildura 174 Wyong 240 Morwell 19 Northern Territory Western Australia Alice Springs 204 Albany 217 Darwin 3 Broome 343 Katherine 304 Bunbury 215 South Australia Derby 343 Adelaide 18 Geraldton 173 Mt.Gambier 18 Perth 214 Port Augusta 189 Port Headland 332 KINGAROY TOOWOOMBA WARRAGAMBA BALLARAT COLAC CAMBELLTOWN CASTLEMAINE 180 GEELONG LAIDLEY LIVERPOOL KILCOY PARRAMATTA CALOUNDRA CABOOLTURE IPSWICH STRATHFIELD BANKSTOWN CENTRAL VICTORIA KILMORE MELBOURNE FRANKSTON HEALESVILLE WARRAGUL NOOSA NAMBOUR BRISBANE CITY 270 CRONULLA MANSFIELD SOUTH EAST QUEENSLAND MAROOCHYDORE BEENLEIGH WALHALLA HEYFIELD SALE MORWELL 190 The maps are only intended to indicate the variability SOUTHPORT of rainfall intensity within the region shown. Specific data for any location can be obtained from the Commonwealth Bureau of Meteorology in Melbourne. 240 WARWICK 240 BOONAH COOLANGATTA GOLD COAST 5

6 MINIMUM ROOF SLOPES a rainfall intensity of 200mm/hr total Stramit Corrugated exceeds the scope of this guide Stramit Longspan Stramit Monoclad Stramit Megaclad Stramit Xtraspan Stramit Speed Deck Stramit Speed Deck Ultra Stramit Capacity Plus Stramit Snaptite MINIMUM ROOF SLOPES a rainfall intensity of 220mm/hr total Stramit Corrugated exceeds the scope of this guide Stramit Longspan Stramit Monoclad Stramit Megaclad Stramit Xtraspan Stramit Speed Deck Stramit Speed Deck Ultra Stramit Capacity Plus Stramit Snaptite MINIMUM ROOF SLOPES a rainfall intensity of 240mm/hr total Stramit Corrugated exceeds the scope of this guide Stramit Longspan Stramit Monoclad Stramit Megaclad Stramit Xtraspan Stramit Speed Deck Stramit Speed Deck Ultra Stramit Capacity Plus Stramit Snaptite MINIMUM ROOF SLOPES a rainfall intensity of 280mm/hr total Stramit Corrugated exceeds the scope of this guide Stramit Longspan Stramit Monoclad Stramit Megaclad Stramit Xtraspan Stramit Speed Deck Stramit Speed Deck Ultra Stramit Capacity Plus Stramit Snaptite

7 MINIMUM ROOF SLOPES a rainfall intensity of 340mm/hr total Stramit Corrugated 5.0 exceeds the scope of this guide Stramit Longspan Stramit Monoclad Stramit Megaclad Stramit Xtraspan Stramit Speed Deck Stramit Speed Deck Ultra Stramit Capacity Plus Stramit Snaptite MINIMUM ROOF SLOPES a rainfall intensity of 370mm/hr total Stramit Corrugated 5.5 exceeds the scope of this guide Stramit Longspan Stramit Monoclad Stramit Megaclad Stramit Xtraspan Stramit Speed Deck Stramit Speed Deck Ultra Stramit Capacity Plus Stramit Snaptite Note: Depth of flow in pan = 0% height of underlap (agreed industry standard) Product availability Not all profiles listed in this guide are available in all locations. The table below gives an indication of availability by region. REGIONAL PRODUCT AVAILABILITY N.TER N. QLD S. QLD NSW ACT VIC TAS S.AUS W. AUS Stramit Corrugated Stramit Longspan Stramit Monoclad Stramit Megaclad Stramit Xtraspan 900????? Stramit Speed Deck 500? Stramit Speed Deck Ultra Stramit Snaptite???? Stramit Capacity Plus readily available? available subject to enquiry and minimum order quantity not normally available 7

8 The Stramit web page can be found at: Details of many Stramit products can also be seen on the AIA site Product Selector at: contact numbers for information prices availability general technical products other advice coating product data colours SYDNEY phone (02) (02) Quarry Road, Erskine Park NSW 2759 fax (02) (02) CANBERRA phone (02) Bass Street, Queanbeyan NSW 220 fax (02) COFFS HARBOUR phone (02) (02) Mansbridge Drive, Coffs Harbour NSW 2450 fax (02) (02) NEWCASTLE phone (02) Nelson Road, Cardiff NSW 2285 fax (02) ORANGE phone (02) Leewood Drive, Orange NSW 2800 fax (02) MELBOURNE phone (03) 9237 (03) /144 Ferntree Gully Road, Knoxfield VIC 3180 fax (03) (03) ALBURY phone (02) Ariel Drive,Albury NSW 240 fax (02) BENDIGO phone (03) Ramsay Court, Kangaroo Flat VIC 3555 fax (03) HOBART phone (03) Crooked Billett Drive, Brighton TAS 7030 fax (03) (03) LAUNCESTON phone (03) (03) Hobart Road, Kings Meadows TAS 7249 fax (03) ADELAIDE phone (08) (08) Stock Road, Cavan SA 5094 fax (08) (08) BRISBANE phone (07) Platinum Street, Crestmead QLD 4132 fax (07) TOWNSVILLE phone (07) Bayswater Road, Garbutt QLD 4814 fax (07) CAIRNS phone (07) Vickers Street, Edmonton QLD 489 fax (07) MACKAY phone (07) (07) Brickworks Court, Glenella QLD 4740 fax (07) (07) MARYBOROUGH phone (07) Activity St, Maryborough QLD 450 fax (07) ROCKHAMPTON phone (07) Johnson St, Parkhurst QLD 4702 fax (07) SUNSHINE COAST phone (07) Unit 1, 5 Kerryl St, Kunda Park QLD 455 fax (07) MURWILLUMBAH phone (02) Kay Street, Murwillumbah NSW 2484 fax (02) DARWIN phone (08) Albatross Street,Winnellie NT 0820 fax (08) PERTH phone (08) Bickley Road, Maddington WA 109 fax (08) BUNBURY phone (08) Proffit Street, Bunbury WA 230 fax (08) Registered trademarks of Stramit Corporation Pty Limited. ABN trading as Stramit Building Products A member of the Fletcher Building Group COLORBOND and ZINCALUME are registered trademarks of BlueScope Steel Limited Stramit Corporation Pty. Limited August This document replaces all previous issues. Please destroy, or clearly mark as superseded, all previous issues. 047