Asiapinball
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@NeilMcRae asked a question about floor loadings and pinball machines upstirs on another post about engineering a hoist to get a pinball machine upstairs. Firstly, I'm not a builder or structural engineer and there are likely others better qualified to comment on the group. However, I had all the 1st floor joists replaced in my house a few years ago and as a mathematician took an interest in the loadings calculations. My floors had sagged - they were hugely underspecified by todays standards when installed in 1870, likely due to a shortage of wood / skilled craftsmen in the village as there was a beetle infestation that destroyed much of the woodwork in all the village houses. Some of the floors in the largest 4.8m x 4.5m upstairs rooms had sagged by 3 to 4 inches in the middle but the joists were just 6.5 inches deep by 2.5 inches wide across 16ft spans so it is not surprising they sagged when comparing to the span tables in order to meet current building regulations.
Current building regulations require minimum 1.5KN per square metre live loading (things you put into the room including people) and that translates to about 150kg per square metre evenly spread across the floor. And the test as to whether it meets this requirement is how much the floor deflects (not whether it collapses or not) - it needs to be no more than 3mm maximum deflection per metre of joist span (distance between walls that the joists span from supporting wall to supporting wall below). So if you have a 4m x 3m room and the joists lengthways and you load the floor to 150kg per square metre it should deflect downwards by no more than 12mm (in the centre of the span). There are plenty of span tables online that show what the maximum span to meet this requirement is and they are based on size of timber, spacing of joists, strength of timber (C16 or stronger C24) thickness of floorboards etc. but these tables are for straightforward graded timber in a basic construction going from wall to wall and don't take account of point loads, stud walls above etc (that you need a structural engineer to do the calculations). Note that it is not the size of the room you are putting the weight in its the span of the supporting walls below that matters.
A twilight zone is about 140kg and takes up floorspace (between legs) of 1.4m x 0.75m = 1.05 sq metres. So this is about 10% below the maximum loading. So theoretically you could fill a room with pinball machines and still be below the the maximum floor loading that would give maximum permitted deflection. But you shouldn't really be storing that spare box of coils or spare populated playfield under the machine. And if you did over-load you would unlikely get catastrophic failure unless there was some structural issue; you would just get more downward deflection of the floor.
I concluded that for my new floors that meet current building regulations I could put as many machines upstairs as I want to, but if I did so, my new floors would deflect by 15mm as joists are across almost 5m spans. So, to minimise the floor deflections it would be best to put them in the rooms that have the shortest joist spans, spread them across as many joists as possible (so have them parallel to the joists/ perpendicular to the floorboards) so that it best spreads the load across the floor and keep them to the edges of the room where the supporting walls are and don't use the space underneath to store anything heavy. But then there is still a risk that when I remove the weight after many years the floors will not spring back up to where they were originally - just like my 150 year old under-specified joists (by today's standards) were permanently sagged, even when all the live loading was removed from them.
I don't have any pinball machines upstairs; I gladly have enough space downstairs on concrete / stone floors and I really am no longer cut out for moving machines up and down stairs (only ever done it for 2 machines in the past, RFM and a TOTAN, 20 years ago, and never want to repeat).
Paul
Current building regulations require minimum 1.5KN per square metre live loading (things you put into the room including people) and that translates to about 150kg per square metre evenly spread across the floor. And the test as to whether it meets this requirement is how much the floor deflects (not whether it collapses or not) - it needs to be no more than 3mm maximum deflection per metre of joist span (distance between walls that the joists span from supporting wall to supporting wall below). So if you have a 4m x 3m room and the joists lengthways and you load the floor to 150kg per square metre it should deflect downwards by no more than 12mm (in the centre of the span). There are plenty of span tables online that show what the maximum span to meet this requirement is and they are based on size of timber, spacing of joists, strength of timber (C16 or stronger C24) thickness of floorboards etc. but these tables are for straightforward graded timber in a basic construction going from wall to wall and don't take account of point loads, stud walls above etc (that you need a structural engineer to do the calculations). Note that it is not the size of the room you are putting the weight in its the span of the supporting walls below that matters.
A twilight zone is about 140kg and takes up floorspace (between legs) of 1.4m x 0.75m = 1.05 sq metres. So this is about 10% below the maximum loading. So theoretically you could fill a room with pinball machines and still be below the the maximum floor loading that would give maximum permitted deflection. But you shouldn't really be storing that spare box of coils or spare populated playfield under the machine. And if you did over-load you would unlikely get catastrophic failure unless there was some structural issue; you would just get more downward deflection of the floor.
I concluded that for my new floors that meet current building regulations I could put as many machines upstairs as I want to, but if I did so, my new floors would deflect by 15mm as joists are across almost 5m spans. So, to minimise the floor deflections it would be best to put them in the rooms that have the shortest joist spans, spread them across as many joists as possible (so have them parallel to the joists/ perpendicular to the floorboards) so that it best spreads the load across the floor and keep them to the edges of the room where the supporting walls are and don't use the space underneath to store anything heavy. But then there is still a risk that when I remove the weight after many years the floors will not spring back up to where they were originally - just like my 150 year old under-specified joists (by today's standards) were permanently sagged, even when all the live loading was removed from them.
I don't have any pinball machines upstairs; I gladly have enough space downstairs on concrete / stone floors and I really am no longer cut out for moving machines up and down stairs (only ever done it for 2 machines in the past, RFM and a TOTAN, 20 years ago, and never want to repeat).
Paul
