I need to verify where my joists are in relation to a shower tray drain before I lift the tiled floor or order the tray. I know which way the joists run and can see one line of fixing nails, can anyone confirm what the on centre measurements of the joist are ? The house was built in 1989, I have 16" (400mm) on centre in mind from somewhere, but not absolutely sure.
Joists on centre distance ?
- Thread starter bathjobby
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400mm sounds right but it depends on the size of joist and they could be 450mm centres or even 600mm centres. Can you check under the carpets in other rooms to see the nail patterns because that may help but to be honest it may be just pot luck unless you lift the floor to check.
you are correct with your figure of 16inch centres. All joists ,rafters ,stud walls etc are at this centre because of the size of plaster board, plywood, etc which come in 8x4 foot sheets. This allows you to position the sheet directly on the centre of a joist.
The only slight alteration is if the builders used metric ,but it is still roughly the same, ie 400mm centres
The only slight alteration is if the builders used metric ,but it is still roughly the same, ie 400mm centres
For this year of construction 400mm ctrs on joists would have been the norm. You can check other rooms for nail ctrs, but if there was an obstruction in the bathroom the ctrs may not be the same. You are left with two ways of finding correct ctrs. 1. lift the floor (a pain if you have to wait a long time for later ordered materials 
) 2. buy a stud detector, approx £15, and proceed to trace the floor joists from the ceiling below the bathroom. this is the easy way--no mess.
) 2. buy a stud detector, approx £15, and proceed to trace the floor joists from the ceiling below the bathroom. this is the easy way--no mess. Sponsored Links
You can never be sure where the joists are! No matter what centers are 'supposed' to be used, the chippies will have put the joists where convenient (but keeping to 400mm or thereabouts centers). So the spacing could be 300 in places then suddenly 390, then 412 and so on. It all depends on obstructions etc.
For example, a room 4250mm wide. The joists cannot ALL be @ 400 centres can they, some squeezing up is inevitable.
For example, a room 4250mm wide. The joists cannot ALL be @ 400 centres can they, some squeezing up is inevitable.
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