4" joist maximum span
- Thread starter davey76
- Start date
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At 400mm centres, and assuming regularised 100x50 timber and grade C16, you'll span around 2 metres.
C24 will span about 2.15m.
Close up the centres, or double them up, and they'll span a bit further...
C24 will span about 2.15m.
Close up the centres, or double them up, and they'll span a bit further...
and we're off!!.................... 
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Shouldn't be too bouncy with deflection limited to 0.003xspan...
If the floor is to be ceramic tiled you want zero movement or bounce.
In my own kitchen, i took up the floorboards, i fitted props under the floor joists at mid-span, fixed noggins where the plywood sheet edges fell and screwed 18mm ply to the floor.
Half my floor is wood the other (extended) part is concrete and there is no difference in the condition of the tiling - both are sound. I did make sure that the floor tiles overlapped the join though i.e. avoiding any tile grout joints directly over the join.
Do it robustly and do it once.
In my own kitchen, i took up the floorboards, i fitted props under the floor joists at mid-span, fixed noggins where the plywood sheet edges fell and screwed 18mm ply to the floor.
Half my floor is wood the other (extended) part is concrete and there is no difference in the condition of the tiling - both are sound. I did make sure that the floor tiles overlapped the join though i.e. avoiding any tile grout joints directly over the join.
Do it robustly and do it once.
True...missed the bit about tiling, it was bed time!
Also need decent WBP plywood over the joists too.
50x150 C16 regularised at 400mm c/c and 2m span would give 1.6mm deflection, under full load...which should be OK
50x100 gives more like 6mm which is probably a bit high for tiling.
Of course, if it's ground floor, nothing to prevent sleeper walls being used if the span is a bit longer.
Depending on the age of the house there should be a layer of concrete oversite which may be strong enough to take the props/sleeper wall.
Although, if in doubt, cast a small footing or use deeper joists.
What is your span?
Precisely - on stilts which then sit on the concrete oversite along with a strip of plastic dpc under the props.
ah there is no concrete oversite - its an olde worlde house so just soil under the floor
total span is approx 15' with a sleeper wall at each end and in the middle. The joists are still a bit bouncy though - mid-span between the sleeper walls
total span is approx 15' with a sleeper wall at each end and in the middle. The joists are still a bit bouncy though - mid-span between the sleeper walls
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