![]() The counter weight lenght on the joists are 500mm. But I have to get a building permit from council and I really don't want it to get rejected.įor reference I will have two foundations/footings (six total), one at either end on the bearers. I am happy to go with what you have suggested, it's similar to what I had already thought. But again the table says that I would use this size for 1200mm spans, which is not what is recommended by everything else I have read (ie 450mm). In my case they go across the deck (so that the decking boards align going away from the house, in line with the hardwood flooring inside the house).īut my deck is 3800mm wide, which, again on my reading of the span table, means I should be using 170x35mm joists. On my reading 90x45mm joists at 1200mm span load means the joists can be 2400mm long. But the tables I found for hardwood state that 1200mm. Everything I read says that 450mm spacings are standard, and I have done that in the rendering below. I guess my issue is that I don't full understand how you derived the joists based on the span tables. I have rendered an image below with the joist and bearer measurements as you suggested. If I use 450mm spacing, how do I work out what joists are okay? Originally I found 70x45mm timber which I thought should okay for the joists given it's hardwood F27 but I can't find a span table to work it out. But I would prefer 3 bearers with smaller wood but the span tables don't have, say, 1600mm span loads.īut the Joists needing to be 170x45 (1200mm span width) means I am beyond my 300mm limit for my deck. I can accept 2/170x45 bearers as these will run the lenght of the deck (2 bearers spaning 2400mm each, deck is 3800mm wide). The second attachment is the bearer F27 hardwood with the same span/floor load widths. I was going to have joists at about 450mm spacings. My issue is that spanning tables for hardwood seem to limit floor load width (which I assume is span load width) to 1200mm. I want to have the joists above the bearers as this will improve airflow. The deck will be 3800mm wide, 3000mm long. As such I will probably use hardwood as I can get F17-F27, H4 equivalent timber, so I don't have to worry about water and can try to get smaller bearers and joists. My issue is that I am building a deck with little clearance. ![]() 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 .I know this is an old thread but it's been the most helpful in learning how to read span tables. 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. ![]()
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