Timber joist calcs - can anyone help?
Discussion
Skodasupercar said:
The self weight of the joists is considered in the calcs but ISN'T included in the dead load figure. The dead load figure is for the linings alone.
The reason you can't find 150x50 (well 145x47) in the span tables is two fold. 1) I suspect you have the 2nd edition span tables to BS5268, not the new timber sizer software to EC5 2) the standard span tables assume an imposed load of 0.9kN. Being as there is only a tiny void between the ceiling and the floor structure above, there will be no access or additional loading. Therefore the imposed load can be reduced.
With timber sizing you should always expect a deflection of span/250. Unless you overspec the members that is!
Now for floor joists at this span and centers you would be looking at 245x47mm for a domestic intermediate floor. So, a floor that could take the weight of furniture, many many people, the weight of the ceiling and floor linings and the weight of some timber partitions needs a 245mm deep joist, whereas a ceiling joist that is only holding 1x sheet of plasterboard and nothing else needs 150mm.
I hope that puts the sizes and the loads into perspective!
Not really, I sized the beams based on it being a ceiling, as that's what it is. The reason you can't find 150x50 (well 145x47) in the span tables is two fold. 1) I suspect you have the 2nd edition span tables to BS5268, not the new timber sizer software to EC5 2) the standard span tables assume an imposed load of 0.9kN. Being as there is only a tiny void between the ceiling and the floor structure above, there will be no access or additional loading. Therefore the imposed load can be reduced.
With timber sizing you should always expect a deflection of span/250. Unless you overspec the members that is!
Now for floor joists at this span and centers you would be looking at 245x47mm for a domestic intermediate floor. So, a floor that could take the weight of furniture, many many people, the weight of the ceiling and floor linings and the weight of some timber partitions needs a 245mm deep joist, whereas a ceiling joist that is only holding 1x sheet of plasterboard and nothing else needs 150mm.
I hope that puts the sizes and the loads into perspective!
Not that I really care that much, but do you follow the argument that you can reduce the imposed load as no access is possible to the ceiling void? The 0.9kN imposed load is to account for access - no access = no additional imposed load. No imposed load = smaller joists.
The standard span tables don't allow the user to change the imposed load specifications. If you use the actual software on the TRADA website, you can adjust the imposed load spec.
Anyway, to the OP, do whatever you feel based on the information provided. Your house, your call!
The standard span tables don't allow the user to change the imposed load specifications. If you use the actual software on the TRADA website, you can adjust the imposed load spec.
Anyway, to the OP, do whatever you feel based on the information provided. Your house, your call!
I've only quick-scanned the thread, but do you really need to noggin at every board edge on 400mm centres? A lot of extra work. The BS for plaster boarding is relatively easy to find online, and will tell you where you will / won't need noggins. Pretty sure you'll be fine on 400 centres in 12.5mm board. If you're joists are decent, straight and level I wouldn't bother.
As an aside, the garage I built has C16 joists to the span tables - something like 220x47 with built in ends. My 30's house has 67x34mm joists over a similar 4m span in the upstairs (heavy) lath and plaster ceiling, held by one nail roughly bashed in to hold it up!
As an aside, the garage I built has C16 joists to the span tables - something like 220x47 with built in ends. My 30's house has 67x34mm joists over a similar 4m span in the upstairs (heavy) lath and plaster ceiling, held by one nail roughly bashed in to hold it up!
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