Drilling holes in floor joists

[MidsTW]

I am moving hot and cold pipes below the floorboards for extra space.

I have drilled the first hole but I seem to have slipped up.... I try to do everything by the book and I believe building regs say you cannot drill a hole outside of 0.4 x the span between 2 supports.

My span is 1560mm between the external wall and a steel I beam. I have drilled a hole at 830mm from external wall (0.53 x span) should I worry? The span is pretty short so I assume this means it isn't as bad.

The hole diameter is 35mm and the depth of the joist is 175mm so I am safe there.

Any advice welcome.

 

[tony1851]

I have drilled a hole at 830mm from external wall (0.53 x span) should I worry?

OMG! We're about to have a nuclear war over some place in eastern Europe, and you're worried about a hole being 204mm out!!

Seriously, no worries - 1.5/1.6m is not a long span for 175mm deep joists.

The guidance for drilling and notching has safety factors in it, as there will always be idiots hacking away with axes and drilling 100mm holes through
150 deep joists.

 

[MidsTW]

Thanks Tony.

That did make me laugh.

Well if it should be okay I will drill the other 3 in the same position. There was a galley kitchen below which means the span is short.

I guess the guidelines are also based on the span being a relatively long length too!

 

[oldbutnotdead]

One way to look at it- if your joists are at 400 centres than according to current TRADA tables to span 1800mm in the most arduous loading (1250N/sq m) you only need 45 x 120. So you could lose 50mm across the entire span and still be within requirements- might be a bit bouncy if it was a bathroom but wouldn't be going anywhere

 

[MidsTW]

Thanks great piece of info! Yes they are 400mm centres!

I have drilled all my holes now too ready to do the plumbing with a mate.

Makes sense that the requirments are relaxed for shorter spans as the bending moment in the centre will not be as high.