Quoted from Raegor:
Do you know what type of floor joists you have? Mine's a bonus room above the garage, dunno if they build up that floor like a normal 2nd floor.
I have two pins up there but pins are only 250 each.
I don't remember the joist specifics but ours is a bonus room above a 3-car garage. House was built in 2002. I remember checking the load capacity of that room when we first moved in and I am WELL under the limit with everything up there (7 pins, 2 drivers, 2 slots, MAME cabinet, JVL and Megatouch games).
I believe most second story floors are rated for a minimum of 40 lbs/sq. ft. So a 250lb pinball which is spread over 12.5 sq.ft. (5' x 2.5')would only load about 20 lbs/sq.ft. Also, having the games near the walls and not in the center of the room also increases the load bearing capacity. Even though a floor is rated at 40 lbs/sq.ft., a 200 lb man is not going to fall through the floor even though he's standing in an area of less than 1 sq.ft. It spreads the load across the entire square footage.
So take the length and width of your room, multiply those together and then by 40. That should give you a general idea of the capacity for the room. So a 10x20 room would give you about 8,000 lb capacity (10x20x40)! If a pinball is roughly 250 lbs, that would be 32 pins!