plasterboard on the underside of the rafters the effects of deflection under concentrated (point) load do not need to be considered as per guidance given in BS 5268-7.5 clause 4.3. The imposed load should be calculated in accordance with BS 6399:Part 3:1988 Code of practice for imposed roof loads, as a rule of thumb for altitudes not exceeding 100m you can use a uniformly distributed load of 0.75 kN/m² and for most other areas exceeding 100m but not exceeding 200m you can use 1 kN/m², for parts of Scotland, Pennines, North East England and heights over 200m you will need to refer to BS 6399 Part 3.Īs there are no brittle finishes e.g. ![]() Rafters are to have minimum end bearing of 35mm. Wane as allowed in BS 4978:2007+A2:2017 is permitted in all sections included in these span tables. Timber to be covered, these span tables do not apply to timber which is fully exposed to the elements. Holes and notches cannot be drilled or cut into the rafters unless proved adequate by specialist calculations. Because metal roofs are often exposed to extreme temperatures, they require a special type of rafter that is designed to withstand such conditions. The calculations on which these span tables are based conservatively assume that the rafters are not continuous over the purlins, but they can be continuous over the supporting purlin if required. These span tables are based on the assumption that the tiling battens fastened to the top of the rafters will provide adequate lateral restraint and also ensure that lateral loads are distributed. It is also assumed ceiling joists will be used to transmit the horizontal component of thrust occurring at eaves level to complementary rafters. These span tables only apply to roof systems with four or more rafters. These span tables do not apply to trussed rafter roofs. The dead loads shown at the top of span table above do not include the self weight of the rafters, however, the rafter self weights are included (in addition to the dead loads) in the calculations used to determine permissble clear spans. The number of supports (beams or purlins) affects the allowable span length. ![]() Maximum roof slope is 5° for monoslope and 22.5° for pitched roof. Patio width is no less than 2.1m and length is no less than 3.5m. Patio height (hc) must always be less than roof height (h). The allowable clear spans have been calculated in accordance with BS 5268-2:2002 Structural use of timber - Part 2: Code of practice for permissible stress design, materials and workmanship and BS 5268-7.5:1990 Structural use of timber - Section 7.5 Domestic rafters. Average roof height between 3m and 6.5m (3m h 6.5m). These span tables have been prepared for the use of Spantec Colorbeam in a range of free standing and attached verandah, patio, awning and carport designs. For final design confirmation and further design options, including continuous spans or non-uniformly loaded joists, please refer to the Dindas Design Guide, contact us at any of our state locations, or request information through .Dead load per square metre (in kN/m²) supported by raftersĬentre-to-centre spacing of rafters (in mm) These calculation results will only be used as a handy guide (not for construction) when designing your project joist spans. This can be a solid bottom edge bearing (like a wall) or face fixed metal hanger. bearing conditions (35mm) or greater have been included. * Joists with a Max.Centre spacing of 600mm or less = 22mm min ![]() * Joists with a Max.Centre spacing of 450mm or less = 19mm min Joist Centres are 300mm and can only be used at any joist centres equal to or less than 300mm centres.įlooring thickness must be checked before installation to ensure it can span the intended Max. Centres” is 600mm, the joist can be used at the lower nominated spacings, i.e., 300mm, 400mm, 480mm, and 600mm centres if it’s Max. Centres are the maximum centres that this joist can be installed at. The Class 1 classification includes two sub-classifications: Class 1a and Class 1b In these situations, they must be separated by a wall with fire-resisting and sound insulation properties. They can also be horizontally attached to other Class 1 buildings, such as terrace houses, rowhouses, or townhouses. Typically, they are standalone single dwellings of a domestic or residential nature.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |